FERTILITY AND STERILITY Copyright"
Vol. 55, No.2, Fehruary
1991 The American Fertility Society
1991
Printed on acid-free paper in U.S.A.
Antibiotics: potential hazards to male fertility
Peter N. Schlegel, M.D. Thomas S. K. Chang, Ph.D. Fray F. Marshall, M.D. The Population Council, Center for Biomedical Research, and The New York Hospital-Cornell Medical Center, New York, New York, and the Johns Hopkins Medical Institutions, Baltimore, Maryland
Adverse effects of antibiotic agents on spermatogenesis or sperm function have been demonstrated throughout the animal kingdom. In man, these effects have been clearly delineated for a few agents and have been implicated for most major classes of antibiotics, including the nitrofurans, macrolides, aminoglycosides, tetracyclines, and sulfa drugs. The effects of antibiotics on fertility and the implications for the management of the infertile couple may be greater than generally appreciated. Because of the potential multifactorial nature of infertility, it is intended for this review to raise as many questions as it will answer regarding the adverse effects of these very commonly used antibiotics on male fertility. The need is evident for continued laboratory investigation and thoughtful clinical observation to better define the effects of antibiotics on fertility in men. The antibiotics to be discussed in this review include only the antibacterial agents; the terms antibiotic and antimicrobial will be used interchangeably. The antitumor agents have been reviewed previously.1 The antiprotozoal, antihelminthic, and other agents are only occasionally used in this country and are not included in this discussion. Approximately 10% to 15% of all couples demonstrate primary infertility, and of those couples a male factor is identified in approximately 50% of cases. 2 Many extrinsic or environmental factors, including the increased use of antibiotics, have been implicated as potential causes of male infertility.3,4 However, the exact etiology of male factor infertility is often difficult to define because of our poor understanding of spermatozoal biochemistry, the processes of spermatogenesis, and sperm maturation. In addition, the potential for multifactorial Vol. 55, No.2, February 1991
causes of infertility and degrees of subfertility5 magnify the complexities involved in our attempts to assess the etiology of male infertility. The time required for spermatogenesis and transport of spermatozoa through the reproductive tract, combined with other confounding systemic factors (local temperature effects, other medications, viral diseases, stress, increased age) clearly represent additional formidable barriers to delineating the possible antifertility effects of these agents. Ethical considerations preclude the direct evaluation of the adverse effects of many environmental agents, including antibiotics, on human fertility and restrict critical studies directed at clarifying the effects of these factors on male reproductive function. However, current information documenting the effects of antibiotics on human and nonprimate male reproductive physiology identifies the potential fertility hazards of antibiotics. To best organize the data, the antibiotics will be categorized by class of drug and the effects of antibiotics on spermatogenesis and/or sperm function. Table 1 provides a synopsis. NITROFURANS
The nitrofuran derivatives have been known to cause spermatogenic arrest and decreased sperm counts in man since 1953. 29 Paul and associates 6 ,29 have demonstrated in vitro an inhibiting effect of furacin on carbohydrate metabolism and oxygen consumption of testicular cells of the rat. The classical work on the effects of nitrofurantoin, the most commonly used agent in this class of antibiotics, was reported by Nelson and Bunge in 1957.8 Of 36 normal volunteers given 10 mg/kg per day of this Schlegel et al.
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Adverse Effects of Antibiotics on Spermatogenesis and Spermatozoa
Table 1
Adverse effects on Antibiotic Nitrofurans Furacin Nitrofurantoin
Furadroxyl Macrolides Spiramycin Erythromycin Tylosin Erythromycin Chloramphenicol Tylosin Oleandomycin Lincomycin Aminoglycosides Gentamicin
Neomycin
Framycetin Tetracyclines Tetracycline HCI Chlortetracycline Minocycline Sulfa Drugs Sulfasalazine Co-trimoxazole Penicillins Penicillin G, Cephalothin Ampicillin Dicloxacillin Miscellaneous Novobiocin
Species
Spermatogenesis
Dose
Rat 6
Inhibits testicular cell carbohydrate metabolism and oxygen consumption Used to treat germ cell tumors Temporary spermatogenic arrest; decreased sperm count
Human 7 Humans
lOmg/kg/d
Rat 9- 11
lOmg/kg/d
Spermatogenic arrest at level of primary spermatocytes Used to treat germ cell tumors
Rat9.13.14 Rat 15
Therapeutic Therapeutic
Rat 15
Therapeutic
Spermatogenic arrest Decreased frequency of mitotic division in testes Decreased frequency of mitotic division in testes
Human 12
Human 16 Ram 16 Bu1l16.17 Rabbit 16 Equine 1S
Immobilizes spermatozoa at 5 to lOX clinically achievable concentrations
Impaired motility or spermicidal
Human 9
Therapeutic
Rat 9
Therapeutic
Human 19
Therapeutic
Rat9.19.2o
Therapeutic/ toxic
Rat 9
Cessation of meiosis at level of primary spermatocytes Spermatogenic arrest; cessation of meiosis Adverse effects on sperm concentration, total sperm count and sperm motility Decreased index of spermatogenesis; spermatogenic arrest; decreased RNA and DNA content in cells of spermatogenic epithelium Spermatogenic arrest
Rat 20
Therapeutic/ toxic
Human 16
lOOmcg/mL
Bovine 21
~50mcg/mL
Human 22-25
Therapeutic
Human 26.27
l60mg/d
Rat 9
Therapeutic
Chicken 2s
6.2mcg/mL
Bovine 17
200mcg/mL
Decrease in fertilizing capacity and motility Decrease in sperm motility
Bovine 17
>125mcg/mL
Spermicidal
Slight decrease in spermatogenic index and in RNA content of spermatogenic cells Deleterious effects on sperm motility Toxic Oligospermia; poor sperm motility, morphological changes Decreased sperm count; decreased sperm motility and morphology Spermatogenic arrest
drug, 7 developed temporary spermatogenic arrest associated with decreased sperm counts. Six other patients also demonstrated decreased sperm counts but no changes were seen on testicular biopsies. Several studies have confirmed the finding of spermatogenic arrest in rats at a dose of 10 mg/kg 236
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per day and defined the level of arrest at the level of primary spermatocytes.9- 11 The disturbance of spermatogenesis observed by Yunda and Kushniruk l l was found to be associated with a decrease in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) content of the surviving cells. In conFertility and Sterility
trast to these reports demonstrating adverse effects of nitrofurantoin on spermatogenesis,6,8-11,29 a study from the Pathology and Toxicology Section of Norwich Eaton Pharmaceuticals (Norwich, New York, NY) in 1984 found no effect on spermatogenesis of male rats treated for 60 days at doses of 10 mg/kg per day.30 The reproductive capacity of male rats treated at 10 mg/kg per day did not appear to differ from control rats. No evaluations were performed for germ cell DNA or RNA content in this study.30 The gonadotoxic effects of nitrofurans in men appear to extend to most of the antibiotics in this class. Furagin (Norwich Eaton), nitrofurazone, and furadonin, as well as nitrofurantoin and furadantin macrocrystals have all been demonstrated to adversely affect spermatogenesis. Nitrofurazone 7 and furadroxyl12 (Norwich Eaton) have been used to treat testicular tumors because of their gonadotoxicity. Nitrofurantoin has been used to immobilize spermatozoa and decrease the time to sterility after vasectomy. However, this immediate immobilization of sperm occurs at concentrations 5 to 10 times greater than those seen clinically in man, and the effects of exposure of spermatozoa to clinically achievable concentrations of nitrofurantoin have not been reported. Recommended therapeutic dosages for nitrofurantoin have now been decreased to 5 to 7 mg/kg per day. To date, no studies have been reported to evaluate the effects of nitrofurantoin on fertility at this dose or at the bacterial suppressive dose of 1 to 2 mg/kg per day. It should be assumed until dem0nstrated otherwise that there may be an adverse effect of nitrofurantoin on spermatogenesis at the therapeutic dose although it is likely to be low at the suppressive doses. Men interested in fertility and requiring long-term antibiotic suppression should preferably be placed on antibacterial agents other than nitrofurantoin, if possible.
the field of dentistry, was found to cause spermatogenic arrest after 8 days of therapeutic equivalent oral doses in rats. 9,13,14 Erythromycin as well as tylosin given at therapeutic dosages decreased the frequency of mitotic division in rat testes. The effects of erythromycin on rat testicular germ cells were reversible 18 days after the cessation of treatment. 15 Short-term exposure of macrolides and related drugs at high dosages to sperm from humans 16 as well as ram,16 bull,16,17 rabbit,16 and horse lS spermatozoa impaired motility or was spermicidal. Longterm exposure to these agents at clinically achievable drug concentrations had no demonstrable effects, except in fowl spermatozoa. Presently, inadequate information is available regarding the effects of macrolides on human male fertility. Based on animal data and the ability of many of the macrolides to inhibit human mitochondrial protein synthesis, it is likely that these agents may impair fertility in man at least during the period of treatment. AMINOGLYCOSIDES
The macrolides (erythromycin, spiramycin, tylosin, midecamycin acetate, oleandomycin, and troleandomycin) are so named because of their large (12 to 16 atom) lactone ring structure. They are discussed with other agents that are elaborated by strains of Streptomyces and their derivatives (lincomycin and chloramphenicol) because of their similar mechanism of action. Spiramycin, which is widely used in Europe for the treatment of protozoal infections as well as in
In general, the aminoglycosides appear to negatively affect spermatogenesis but have negligible, if any, effects on mature spermatozoa. The effects of gentamicin treatment on spermatogenesis were investigated by Timmermans,9 who found that men treated with gentamicin before prostatic surgery developed a cessation of meiosis at the stage of primary spermatocytes with an increase of normal and abnormal primary spermatocytes on testis biopsy. This paper did not describe the indication or duration for treatment of these patients with gentamicin. Neomycin was found to have an adverse effect on sperm concentration, total sperm count, and spermatozoal motility in men with chronic inflammatory urologic conditions. No testicular biopsies were performed in these patients. 19 Studies using rats treated for 8 days with therapeutic doses of gentamicin confirmed the observations in humans regarding the adverse effects of aminoglycosides on spermatogenesis. 9 These animals were found to have spermatogenic arrest with cessation of spermatogonial division and interruption of meiosis in primary spermatocytes. Neomycin has been found to cause decreases in indices of spermatogenesis, including the number of tubules containing spermatozoa, average number of spermatogonia per tubule, and in the RNA and DNA
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content in cells of the spermatogenic epithelium of rats treated with either therapeutic or toxic doses for 20 days. Spermatogenic arrest appeared to occur in these animals at the pre meiotic stage of the spermatogenic epithelium as evidenced by suppression of the mitotic activity of the spermatogonia and subsequent death of spermatogonia and spermatocytes. 19 ,20 Framycetin, another neomycin not in clinical use in this country, has also been found to cause spermatogenic arrest in rats after an 8-day course of administration. 9 In contrast to the adverse effects of aminoglycosides on spermatogenesis, this class of antibiotics has virtually no direct effects on the viability and/ or motility of spermatozoa in vitro. Studies in which kanamycin,18 amikacin,31 streptomycin,18,28 gentaniicin,18,32 neomycin, and tobramycin 17 were admixed with spermatozoa have failed to show any detrimental effect on sperm function at concentrations up to 1 mg/mL when the pH of the test solutions was maintained in the physiological range. The lack of adverse effects of streptomycin on human spermatozoa at concentrations up to 5 mg/mL has led to its acceptance as a component in semen extenders for the cryopreservation of human sperm. TETRACYCLINES
have been found to be directly toxic to mammalian spermatozoa at or below clinically achievable urine concentrations of these agents. Chlortetracycline has deleterious effects on human spermatozoa at concentrations of 100 mcg/mL,16 and minocycline hydrochloride has been found to be toxic to bovine spermatozoa at all concentrations tested (lowest was 50 mcg/mL).21 Tetracycline hydrochloride does not appear to affect the motility and viability of human spermatozoa at a concentration of 4 mcg/10 6 sperm but has not been evaluated to date at higher concentrations. Due to the widespread applicability of tetracyclines to infections involving the genitourinary tract, further information is necessary to delineate the negative effects of these agents on human spermatozoal function. Tetracyclines appear to have less severe adverse effects on spermatogenesis than some of the other classes of agents but are relatively toxic to ejaculated spermatozoa at the concentrations seen therapeutically in man. It is likely that the beneficial effects of treatment of men with an infectious etiology for infertility may actually reflect a balance between the beneficial effects of eradication of infection and pyospermia versus the probably temporary negative effects of tetracyclines on spermatozoal function. The judicious use of antibiotics may lead to further improvement in the results of treatment of men with genitourinary infections and infertility, particularly for those patients requiring long-term or chronic administration of antibiotics. For example, Toth and Lesser 34 reported that in patients with demonstrated Ureaplasma urealyticum infection, doxycycline rather than tetracycline should be the antibiotic of choice.
Tetracyclines have been shown to bind avidly to mammalian spermatozoa including human sperm. The strong adsorption of tetracyclines to the head portion of spermatozoa has been used clinically to study the acrosome reaction, the fusion of the plasma membrane, and acrosomal cap of spermatozoa that occurs after capacitation. 33 Despite similar mechanisms of antibacterial action, the effects of tetracyclines and aminoglycosides on spermatogenesis are markedly different. No information is available on humans; however, treatment of rats with oxytetracycline9 for an 8day period had a minimal effect on spermatogenesis as evaluated by histologic examination. Tetracycline hydrochloride administered to rats in either therapeutic or toxic doses demonstrated20 only a negligible disruption of spermatogenesis after a I-month treatment period as evaluated by histology. There was a slight decrease in spermatogenic index, number of spermatogonia per tubule, and RNA content in spermatogenic cells of the rat testes in this study. In distinct contrast to their relatively mild effects on spermatogenesis, several tetracyclines
Recently, significant literature has developed regarding the detrimental effects of one sulfa drug, sulfasalazine, on male fertility. Sulfasalazine is used in the treatment of inflammatory bowel disease and has been in clinical use since the 1940s. It is metabolized to a sulfa moiety, sulfapyridine, as well as 5-aminosalicylic acid and absorbed from the colon after oral administration. The active agent against the bowel disease is the salicylate; however, animal studies have demonstrated that the antifertility effect of sulfasalazine is most likely mediated by sulfapyridine. 22 ,35 The producers of sulfasalazine estimate that 50,000 men are currently being treated with this drug. 22 Despite this long period of administration to a significant number of patients,
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SULFA DRUGS
the first reports of oligospermia related to treatment with sulfasalazine did not appear in the medical literature until 1979. These first reports have been substantiated with several descriptions of the temporal relationship between sulfasalazine treatment and 01igospermia. 23-25 The effect of sulfasalazine on semen quality (oligospermia' poor sperm motility, and possibly morphological changes, i.e., nucleomalacia) appears to be independent of serum luteinizing hormone, follicle-stimulating hormone, prolactin, and testosterone levels 22 in these patients although this finding has been disputed. 36 The alterations in fertility of men treated with this drug also appear to be independent of general health or severity of inflammatory bowel disease as evidenced by rapid improvement of semen quality after discontinuation of the drug despite worsening of bowel symptoms. Reinstitution of sulfasalazine therapy in patients without symptoms has been shown by Cosentino et a1. 22 to result in deterioration of semen quality. The effects of sulfasalazine on semen parameters appear to be fully reversible. Many pregnancies have been reported in couples after the man has stopped taking the drug despite treatment for up to 11 years. The time course of full reversibility would be consistent with a toxic effect on the testis, probably early in the process of spermatogenesis. A possible secondary effect on later stages of spermiogenesis is implied by the partial response of semen parameters within 2 weeks after withdrawal of the drug. Inadequate information is available on testicular biopsies of men who have taken this drug to fully assess its effect on testicular histology. The toxicity of sulfasalazine may be unique to this agent because other sulfa drugs appear to be without significant effects on semen parameters in men. Sulfadiazene has been shown to have no effect on semen parameters after a 2-week course of administration to normal healthy volunteers.37 Patients treated with sulfanilamide in doses of 828 to 1,800 mg/d for 16 to 58 days showed no significant alterations in total sperm count or percentage oflive spermatozoa. 38 The combination drug co-trimoxazole (sulfamethoxazole and trimethoprim) was found to decrease the sperm count in 37% of 40 patients being treated for possible genitourinary infection after referral for infertility.26 However, 42% of these patients also demonstrated improvement in semen quality with treatment, so a strong relationship between this agent and impairment of sperm production cannot be made on the basis of this report. One Vol. 55, No.2, February 1991
study from Germany27 indicated a possible effect of co-trimoxazole on semen parameters in urologic and dermatologic patients. Forty-five patients underwent semen analysis before, during, and after 7 to 80 days of treatment with 160 mg of trimethoprim and 800 mg of sulfamethoxazole per day given orally. The adverse effects on total sperm number, sperm motility, and morphology were not seen during the treatment period but only 4 weeks after stopping the combination drug. No further followup of these patients was presented. Based on these two clinical studies of co-trimoxazole, at most only a possible influence of this agent on spermatogenesis could be inferred. Despite several studies in man and animals on the effects of sulfa drugs on spermatogenesis, marked adverse effects on spermatogenesis and fertility have so far been demonstrated only for sulfasalazine. Further investigation is required to define the adverse action of sulfasalazine on spermatogenesis. PENICILLINS
Many of the side effects seen in the human use of penicillins result from the formation of a proteinpenicillin hapten that may induce an antibody response in the treated patient, leading to an allergic type of response. Little is known of the effects of penicillins on human spermatogenesis, and most of the penicillins appear to have minimal effects on spermatozoal function in vitro, as measured by· sperm motility and fertility. In rats, therapeutic doses of penicillin G and cephalothin (Keflin, Eli Lilly Co., Indianapolis, IN) have been found to cause spermatogenic arrest after treatment for 8 days with these agents. 9 Penicillin G,16 cephapirin, ceforanide, and ampicillin 39 have all been found to have minimal effects on mammalian spermatozoa. An apparently speciesspecific decrease in fertilizing capacity and motility has been seen with chicken spermatozoa28 at an ampicillin concentration of only 6.2 mcg/mL. This effect is not seen in bulls17 or horses,39 but the effects of ampicillin on human spermatozoa have not been evaluated to date. Dicloxacillin has also been shown to decrease bull sperm motility at concentrations of antibiotic found in the urine (200 mcg/mL); however, this effect has not been reported in humans. The apparent relative safety of penicillins for spermatozoa has led to the widespread acceptance of the use of penicillin (frequently in combination Schlegel et al.
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with streptomycin, 1,000 IV /mL and 1,000 mcg/mL, respectively) as a semen extender for the cryopreservation of animal spermatozoa. MISCELLANEOUS
The effects, if any, on human spermatogenesis and sperm function are not known for most of the other antibiotics that have been evaluated in animals. Agents that affect DNA gyrase are ofparticular interest because of the emerging use of the quinolones, a class of antibiotics that inhibits the enzyme DNA gyrase, and is increasingly used for urologic patients. Nalidixic acid, which inhibits DNA gyrase and tRNA synthetases,4o has been found to have no effect in vitro on equine spermatozoa. IS Novobiocin, a similar antibiotic agent no longer in therapeutic use for humans, was found to be toxic in vitro to bovine spermatozoa at all concentrations tested (lowest was 125 mcg/mL)P It is interesting that the effect of novobiocin on DNA gyrase, also known as topoisomerase, is more pronounced for eukaryotic cells than is seen with nalidixic acid. However, because spermatozoa are not thought to actively transcribe DNA for protein synthesis, the mechanism of toxicity for novobiocin may be other than its effect on DNA gyrase. Ofloxacin is the only quinolone for which reproductive studies have been reported to date. Ofloxacin has been evaluated in adult male mice4I and found to have no adverse effect on germ cell chromosomes during 1 to 5 days of treatment. Clearly, further investigation is needed into the potential adverse effects on fertility of these agents that are likely to be used for suppressive therapy over long periods of time in increasing numbers of patients. DISCUSSION
At least some antibiotics from each ofthe classes of agents discussed above have been found to adversely affect male fertility potential in humans or in a carefully studied animal model. However, there is little information regarding the mechanisms by which these agents affect spermatogenesis or spermatozoal function. Future studies will need to clarify and examine the following questions. At what stage or stages in spermatogenic differentiation do antibiotics cause spermatogenic arrest? Are there species-specific differences in the effect of an antibiotic on spermatogenesis? By what biochemical mechanism does an antibiotic 240
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affect spermatogenesis, and if that mechanism differs from the antimicrobial action, how can it be prevented? For example, if the toxicity from sulfasalazine involves the inhibition of endogenous folic acid production in the testis, which is thought to be minimal in other eukaryotic cells, can that effect be altered by administration of high dose folic acid to these patients? Are the effects of antibiotics on spermatogenesis seen only during treatment, as is currently believed, or are there permanent changes in the number of stem cells in the testis? Finally, the clinical implications of the questions raised in this review must be addressed. Is there an optimal antibiotic agent or class of antibiotics to use against susceptible microbes for long-term suppressive therapy in the male urologic patient desiring fertility? Should particular agents, such as minocycline and other tetracyclines, not be used in any male patient with infertility because of their toxic effects on spermatozoal function? Antibiotics appear to affect spermatogenesis by causing spermatogenic arrest in germ cells not protected from these agents by the blood-testis barrier. Clinical observation of patients requiring long-term suppressive use of antibiotics (e.g., adult vesicoureteral reflux patients) may provide further information regarding the adverse effects of antibiotics in man with minimal confounding effects from underlying disease processes. Clearly, treatment of patients with acute bacterial infections requires the use of antibiotics that reach the site of infection and are effective against the organism to be eradicated. Furthermore, the effects of any illness on fertility potential have to be taken into account when evaluating adverse effects of antibiotics on male fertility. However, based on the accumulating knowledge of antibiotic effects on spermatogenesis and spermatozoal function in many different species, including man, we . must consider that there is likely to be a detrimental effect of antibiotics on male fertility potential at least during the course of treatment. A patient with pyospermia requires treatment for his infection. To minimize the potentially detrimental effects of antibiotics, treatment should await results of semen culture. The antibiotic with demonstrated in vitro effectiveness and the minimum possible detrimental effects on fertility may then be used for treatment of infection. Based on the data available, it is possible that the tetracyclines may adversely affect spermatozoal function. The infertile patient with genitourinary infections may be better managed by treatFertility and Sterility
ment of susceptible organisms with penicillin derivatives (cephalosporins). Penicillin derivatives appear to have the least toxicity to male fertility potential of the available effective agents although their possible effects on human spermatogenesis have not been documented in detail. Further definition of the mechanism by which antibiotics affect spermatogenesis, the reversibility of these effects, the relative effects of different antibiotic agents on male fertility, and the exact exposure of spermatozoa to antibiotics inside the blood-testis barrier is necessary. This information will allow clinicians to better formulate a rational basis for the management of all patients, particularly men who are considered to be infertile or require long-term treatment with antibiotics. Further delineation of the mechanisms by which antibiotics adversely affect spermatogenesis, if pursued, may also facilitate the development of nonhormonal male contraceptive agents. Most importantly, clinicians must consider that antibiotics may represent agents with potential adverse effects on male fertility. It should be remembered that sulfasalazine was in widespread use for over 40 years in many patients before an association with infertility was recognized. One of the best sources for information regarding the adverse effects of any agent on human fertility remains thoughtful clinical observation.
state of knowledge regarding the adverse effects of antibiotics on male fertility is presented in this review. Acknowledgment. The authors thank Marc Goldstein, M.D., The New York Hospital-Cornell Medical Center, New York, New York, for his thoughtful review ofthis manuscript.
REFERENCES
Individual agents within each of the major classes of antibiotics have been shown to have significant adverse effects on spermatogenesis or spermatozoal function in mammals. For humans, infertility or significant alterations in semen parameters have been well documented for the nitrofurans and for patients on sulfasalazine. Other commonly used antibiotics, such as minocycline, have been shown to be toxic to sperm at any concentration. Until further information is available, clinicians must keep in mind that treatment with antibiotics may adversely affect the fertility potential of men. It is possible that some classes of antibiotic agents, such as the penicillins or the quinolones, may have minimal effects on male fertility and maintain the clinical efficacy for patients requiring long-term antibiotic suppressive therapy. Further investigation is needed into the relative toxicity of antibiotics and the mechanisms by which antibiotics affect spermatogenesis and spermatozoal function. A background of the current
1. Damewood MD, Grochow LB: Prospects for fertility after chemotherapy or radiation for neoplastic disease. Fertil Steril 45:443, 1986 2. Lipshultz LI, Howards SS: Evaluation of the subfertile man. Sem UroI2:73, 1984 3. Leto S, Frensilli FJ: Changing parameters of donor semen. Fertil Steril 36:766, 1981 4. Nelson CMK, Bunge RG: Semen analysis: Evidence for changing parameters of male fertility potential. Fertil Steril 25:503, 1974 5. Collins JA, Wrixon W, Jones LB, Wilson EH: Treatmentindependent pregnancy among infertile couples. N Engl J Med 309:1201, 1983 6. Paul MF, Paul HE, Kopko F, Bryson MJ, Harrington C: Inhibition by furacin of citrate formation in testis preparations. J BioI Chem 206:491, 1954 7. Politano VA, Leadbetter GW, Leadbetter WF: Use of furacin in treatment of testicular tumors: a case report. J Urol 79:771, 1958 8. Nelson WO, Bunge RG: The effect of therapeutic dosages of nitrofurantoin (furadantin) upon spermatogenesis in man. J Urol 77:275, 1957 9. Timmermans L: Influence of antibiotics on spermatogenesis. J Urol112:348, 1974 10. Nelson WO, Steinberger E: The effect of furadroxyl upon the testis of the rat. Anat Rec 112:367, 1952 11. Yunda IF, Kushniruk YI: Effect of nitrofuran preparations on spermatogenesis. Bull Exp BioI Med 77:68,1974 12. Karol HJ: Nitrofurans in treatment of malignant testicular tumors. J Urol84:120, 1960 13. Johnson RH, Rozanis J: A review of chemotherapeutic plaque control. Oral Surg Oral Med Oral Pathol 47:136, 1979 14. Furio MM, Wordell CJ: Treatment of infectious complications of acquired immunodeficiency syndrome. Clin Pharm 4:539,1985 15. Lastikka L, Virsu ML, Halkka 0, Eriksson K, Estola T: Goniomitosis in rats affected by mycoplasma or macrolides. Med BioI Eng Comput 54:146, 1976 16. White IG: The toxicity of some antibacterials for bull, ram, rabbit and human spermatozoa. Aust J Exp BioI Med Sci 32:41,1954 17. Berndtson WE, Foote RH: Survival and fertility of antibiotic-treated bovine spermatozoa. J Dairy Sci 59:2130, 1976 18. Back DG, Pickett BW, Voss JL, Seidel GE: Effect of antibacterial agents on the motility of stallion spermatozoa at various storage times, temperatures and dilution ratios. J Anim Sci 41:137,1975 19. Yunda IF, Kushniruk YI: Neomycin effect on testicle function. Antibiot Med BiotekhnoI18:43, 1973 20. Kushniruk YI: Influence of certain antibacterial prepara-
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21.
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23. 24.
25. 26.
27.
28.
29.
30.
tions on the nucleic acid content in cells of the spermatogenic epithelium. Tsitol Genet 10:342, 1976 Ahmad K, Foote RH: Postthaw survival and fertility of frozen bull spermatozoa treated with antibiotics and detergent. J Dairy Sci 69:535, 1986 Cosentino MJ, Chey WY, Takihara H, Cockett ATK: The effects of sulfasalazine on human male fertility and seminal prostaglandins. J UrolI32:682, 1984 Levi AJ, Fisher AM, Hughes L, Hendry WF: Male infertility due to sulphasalazine. Lancet 2:276, 1979 Toovey S, Hudson E, Hendry WF, Levi AJ: Sulphasalazine and male infertility: Reversibility and possible mechanism. Gut 22:445, 1981 Birnie GG, McLeod TIF, Watkinson G: Incidence of sulphasalazine-induced male infertility. Gut 22:452,1981 Murdia A, Mathur V, Kothari LK, Singh KP: Sulpha-trimethoprim combinations and male fertility. Lancet 2:375, 1978 Lange D, Schirren C: Untersuchungen uber den einflub von ri methoprim/sulfamethoxazol auf die qualitat des spermas bei andrologischen patienten-zugleich ein beitrag zur pharmakologischen prufung eines medikamentes auf die spermatogenetische aktivitat des hodens. Z Hautkr 49:863, 1974 Wilcox FH, Shorb MS: The effect of antibiotics on bacteria in semen and on motility and fertilizing ability of chicken spermatozoa. Am J Vet Res 19:945, 1958 Paul HE, Paul MF, Kopko F, Bender"RC, Everett G: Carbohydrate metabolism studies on the testis of rats fed certain nitrofurans. Endocrinology 53:585, 1953 Prytherch JP, Sutton ML, Denine EP: General reproduction, perinatal-postnatal, and teratology studies ofnitrofurantoin macrocrystals in rats and rabbits. J Toxicol Environ Health 13:811, 1984
31. Ahmad K, Foote RH: Motility and fertility of frozen bull spermatozoa in tris-yolk and milk extenders containing amikacin sulfate. J Dairy Sci 68:2083, 1985 32. Sexton T J, Jacobs LA, McDaniel G R: A new poultry extender. 4. Effects of antibacterials in control of bacterial contamination in chicken semen. Poult Sci 59:274,1980 33. Ericsson RJ, Baker VF: Binding of tetracycline to mammalian spermatozoa. Nature 214:403, 1967 34. Toth A, Lesser ML: Ureaplasma urealyticum and infertility: the effect of different antibiotic regimens on the semen quality. J UrolI28:705, 1982 35. O'Morain CO, Smethurst P, Dore CJ, Levi AJ: Reversible male infertility due to sulphasalazine: studies in man and rat. Gut 25:1078, 1985 36. Ragni G, Bianchi Porro G, Ruspa M, Barattini G, Lombardi C, Petrillo M: Abnormal semen quality and low serum testosterone in men with inflammatory bowel disease treated for a long time with sulfasalazine. Andrologia, 16: 162,1984 37. Osenkop RS, MacLeod J: Sulfadiazene: its effect on spermatogenesis and its excretion in the ejaculate. J Urol58:80, 1947 38. Heckel NJ, Hori CG: The effect of sulphanilamide upon spermatogenesis in Man. Am J Med Sci 198:347, 1939 39. Timoney PJ, O'Reilly PJ, Harrington AM, McCormack R, McArdle JF: Survival of haemophilus equigenitalis in different antibiotic-containing semen extenders. J Reprod Fertil27(suppl):377, 1979 40. Wright HT, Nurse KC, Goldstein DJ: Nalidixic acid, oxolinic acid, and novobiocin inhibit yeast glycyl and leucyltransfer RNA synthetases. Science 213:455, 1981 41. Shimada H, Ebine Y, Sato T, Kurosawa Y, Arauchi T: Dominant lethal study in male mice treated with ofloxacin, a new antimicrobial drug. Mutat Res 144:51, 1985
Received March 23, 1990. Dr. Schlegel is an American Foundation for Urologic Diseases Fellow and was supported in part by grant 2 T32 DK 07313-11 from the National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland. He is affiliated with The Population Council, Center for Biomedical Research and the Department of Surgery/U rology, The N ew York Hospital-Cornell Medical Center, New York, New York. Reprint requests: Peter N. Schlegel, M.D., The Population Council, Center for Biomedical Research, Rockefeller University, 1230 York Avenue, Box 273, New York, New York 10021. Drs. Chang and Marshall are affiliated with the James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland. "
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Printed on acid-free paper in U.S.A.
Antibiotics: potential hazards to male fertility
Peter N. Schlegel, M.D. Thomas S. K. Chang, Ph.D. Fray F. Marshall, M.D. The Population Council, Center for Biomedical Research, and The New York Hospital-Cornell Medical Center, New York, New York, and the Johns Hopkins Medical Institutions, Baltimore, Maryland
Adverse effects of antibiotic agents on spermatogenesis or sperm function have been demonstrated throughout the animal kingdom. In man, these effects have been clearly delineated for a few agents and have been implicated for most major classes of antibiotics, including the nitrofurans, macrolides, aminoglycosides, tetracyclines, and sulfa drugs. The effects of antibiotics on fertility and the implications for the management of the infertile couple may be greater than generally appreciated. Because of the potential multifactorial nature of infertility, it is intended for this review to raise as many questions as it will answer regarding the adverse effects of these very commonly used antibiotics on male fertility. The need is evident for continued laboratory investigation and thoughtful clinical observation to better define the effects of antibiotics on fertility in men. The antibiotics to be discussed in this review include only the antibacterial agents; the terms antibiotic and antimicrobial will be used interchangeably. The antitumor agents have been reviewed previously.1 The antiprotozoal, antihelminthic, and other agents are only occasionally used in this country and are not included in this discussion. Approximately 10% to 15% of all couples demonstrate primary infertility, and of those couples a male factor is identified in approximately 50% of cases. 2 Many extrinsic or environmental factors, including the increased use of antibiotics, have been implicated as potential causes of male infertility.3,4 However, the exact etiology of male factor infertility is often difficult to define because of our poor understanding of spermatozoal biochemistry, the processes of spermatogenesis, and sperm maturation. In addition, the potential for multifactorial Vol. 55, No.2, February 1991
causes of infertility and degrees of subfertility5 magnify the complexities involved in our attempts to assess the etiology of male infertility. The time required for spermatogenesis and transport of spermatozoa through the reproductive tract, combined with other confounding systemic factors (local temperature effects, other medications, viral diseases, stress, increased age) clearly represent additional formidable barriers to delineating the possible antifertility effects of these agents. Ethical considerations preclude the direct evaluation of the adverse effects of many environmental agents, including antibiotics, on human fertility and restrict critical studies directed at clarifying the effects of these factors on male reproductive function. However, current information documenting the effects of antibiotics on human and nonprimate male reproductive physiology identifies the potential fertility hazards of antibiotics. To best organize the data, the antibiotics will be categorized by class of drug and the effects of antibiotics on spermatogenesis and/or sperm function. Table 1 provides a synopsis. NITROFURANS
The nitrofuran derivatives have been known to cause spermatogenic arrest and decreased sperm counts in man since 1953. 29 Paul and associates 6 ,29 have demonstrated in vitro an inhibiting effect of furacin on carbohydrate metabolism and oxygen consumption of testicular cells of the rat. The classical work on the effects of nitrofurantoin, the most commonly used agent in this class of antibiotics, was reported by Nelson and Bunge in 1957.8 Of 36 normal volunteers given 10 mg/kg per day of this Schlegel et al.
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Adverse Effects of Antibiotics on Spermatogenesis and Spermatozoa
Table 1
Adverse effects on Antibiotic Nitrofurans Furacin Nitrofurantoin
Furadroxyl Macrolides Spiramycin Erythromycin Tylosin Erythromycin Chloramphenicol Tylosin Oleandomycin Lincomycin Aminoglycosides Gentamicin
Neomycin
Framycetin Tetracyclines Tetracycline HCI Chlortetracycline Minocycline Sulfa Drugs Sulfasalazine Co-trimoxazole Penicillins Penicillin G, Cephalothin Ampicillin Dicloxacillin Miscellaneous Novobiocin
Species
Spermatogenesis
Dose
Rat 6
Inhibits testicular cell carbohydrate metabolism and oxygen consumption Used to treat germ cell tumors Temporary spermatogenic arrest; decreased sperm count
Human 7 Humans
lOmg/kg/d
Rat 9- 11
lOmg/kg/d
Spermatogenic arrest at level of primary spermatocytes Used to treat germ cell tumors
Rat9.13.14 Rat 15
Therapeutic Therapeutic
Rat 15
Therapeutic
Spermatogenic arrest Decreased frequency of mitotic division in testes Decreased frequency of mitotic division in testes
Human 12
Human 16 Ram 16 Bu1l16.17 Rabbit 16 Equine 1S
Immobilizes spermatozoa at 5 to lOX clinically achievable concentrations
Impaired motility or spermicidal
Human 9
Therapeutic
Rat 9
Therapeutic
Human 19
Therapeutic
Rat9.19.2o
Therapeutic/ toxic
Rat 9
Cessation of meiosis at level of primary spermatocytes Spermatogenic arrest; cessation of meiosis Adverse effects on sperm concentration, total sperm count and sperm motility Decreased index of spermatogenesis; spermatogenic arrest; decreased RNA and DNA content in cells of spermatogenic epithelium Spermatogenic arrest
Rat 20
Therapeutic/ toxic
Human 16
lOOmcg/mL
Bovine 21
~50mcg/mL
Human 22-25
Therapeutic
Human 26.27
l60mg/d
Rat 9
Therapeutic
Chicken 2s
6.2mcg/mL
Bovine 17
200mcg/mL
Decrease in fertilizing capacity and motility Decrease in sperm motility
Bovine 17
>125mcg/mL
Spermicidal
Slight decrease in spermatogenic index and in RNA content of spermatogenic cells Deleterious effects on sperm motility Toxic Oligospermia; poor sperm motility, morphological changes Decreased sperm count; decreased sperm motility and morphology Spermatogenic arrest
drug, 7 developed temporary spermatogenic arrest associated with decreased sperm counts. Six other patients also demonstrated decreased sperm counts but no changes were seen on testicular biopsies. Several studies have confirmed the finding of spermatogenic arrest in rats at a dose of 10 mg/kg 236
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per day and defined the level of arrest at the level of primary spermatocytes.9- 11 The disturbance of spermatogenesis observed by Yunda and Kushniruk l l was found to be associated with a decrease in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) content of the surviving cells. In conFertility and Sterility
trast to these reports demonstrating adverse effects of nitrofurantoin on spermatogenesis,6,8-11,29 a study from the Pathology and Toxicology Section of Norwich Eaton Pharmaceuticals (Norwich, New York, NY) in 1984 found no effect on spermatogenesis of male rats treated for 60 days at doses of 10 mg/kg per day.30 The reproductive capacity of male rats treated at 10 mg/kg per day did not appear to differ from control rats. No evaluations were performed for germ cell DNA or RNA content in this study.30 The gonadotoxic effects of nitrofurans in men appear to extend to most of the antibiotics in this class. Furagin (Norwich Eaton), nitrofurazone, and furadonin, as well as nitrofurantoin and furadantin macrocrystals have all been demonstrated to adversely affect spermatogenesis. Nitrofurazone 7 and furadroxyl12 (Norwich Eaton) have been used to treat testicular tumors because of their gonadotoxicity. Nitrofurantoin has been used to immobilize spermatozoa and decrease the time to sterility after vasectomy. However, this immediate immobilization of sperm occurs at concentrations 5 to 10 times greater than those seen clinically in man, and the effects of exposure of spermatozoa to clinically achievable concentrations of nitrofurantoin have not been reported. Recommended therapeutic dosages for nitrofurantoin have now been decreased to 5 to 7 mg/kg per day. To date, no studies have been reported to evaluate the effects of nitrofurantoin on fertility at this dose or at the bacterial suppressive dose of 1 to 2 mg/kg per day. It should be assumed until dem0nstrated otherwise that there may be an adverse effect of nitrofurantoin on spermatogenesis at the therapeutic dose although it is likely to be low at the suppressive doses. Men interested in fertility and requiring long-term antibiotic suppression should preferably be placed on antibacterial agents other than nitrofurantoin, if possible.
the field of dentistry, was found to cause spermatogenic arrest after 8 days of therapeutic equivalent oral doses in rats. 9,13,14 Erythromycin as well as tylosin given at therapeutic dosages decreased the frequency of mitotic division in rat testes. The effects of erythromycin on rat testicular germ cells were reversible 18 days after the cessation of treatment. 15 Short-term exposure of macrolides and related drugs at high dosages to sperm from humans 16 as well as ram,16 bull,16,17 rabbit,16 and horse lS spermatozoa impaired motility or was spermicidal. Longterm exposure to these agents at clinically achievable drug concentrations had no demonstrable effects, except in fowl spermatozoa. Presently, inadequate information is available regarding the effects of macrolides on human male fertility. Based on animal data and the ability of many of the macrolides to inhibit human mitochondrial protein synthesis, it is likely that these agents may impair fertility in man at least during the period of treatment. AMINOGLYCOSIDES
The macrolides (erythromycin, spiramycin, tylosin, midecamycin acetate, oleandomycin, and troleandomycin) are so named because of their large (12 to 16 atom) lactone ring structure. They are discussed with other agents that are elaborated by strains of Streptomyces and their derivatives (lincomycin and chloramphenicol) because of their similar mechanism of action. Spiramycin, which is widely used in Europe for the treatment of protozoal infections as well as in
In general, the aminoglycosides appear to negatively affect spermatogenesis but have negligible, if any, effects on mature spermatozoa. The effects of gentamicin treatment on spermatogenesis were investigated by Timmermans,9 who found that men treated with gentamicin before prostatic surgery developed a cessation of meiosis at the stage of primary spermatocytes with an increase of normal and abnormal primary spermatocytes on testis biopsy. This paper did not describe the indication or duration for treatment of these patients with gentamicin. Neomycin was found to have an adverse effect on sperm concentration, total sperm count, and spermatozoal motility in men with chronic inflammatory urologic conditions. No testicular biopsies were performed in these patients. 19 Studies using rats treated for 8 days with therapeutic doses of gentamicin confirmed the observations in humans regarding the adverse effects of aminoglycosides on spermatogenesis. 9 These animals were found to have spermatogenic arrest with cessation of spermatogonial division and interruption of meiosis in primary spermatocytes. Neomycin has been found to cause decreases in indices of spermatogenesis, including the number of tubules containing spermatozoa, average number of spermatogonia per tubule, and in the RNA and DNA
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content in cells of the spermatogenic epithelium of rats treated with either therapeutic or toxic doses for 20 days. Spermatogenic arrest appeared to occur in these animals at the pre meiotic stage of the spermatogenic epithelium as evidenced by suppression of the mitotic activity of the spermatogonia and subsequent death of spermatogonia and spermatocytes. 19 ,20 Framycetin, another neomycin not in clinical use in this country, has also been found to cause spermatogenic arrest in rats after an 8-day course of administration. 9 In contrast to the adverse effects of aminoglycosides on spermatogenesis, this class of antibiotics has virtually no direct effects on the viability and/ or motility of spermatozoa in vitro. Studies in which kanamycin,18 amikacin,31 streptomycin,18,28 gentaniicin,18,32 neomycin, and tobramycin 17 were admixed with spermatozoa have failed to show any detrimental effect on sperm function at concentrations up to 1 mg/mL when the pH of the test solutions was maintained in the physiological range. The lack of adverse effects of streptomycin on human spermatozoa at concentrations up to 5 mg/mL has led to its acceptance as a component in semen extenders for the cryopreservation of human sperm. TETRACYCLINES
have been found to be directly toxic to mammalian spermatozoa at or below clinically achievable urine concentrations of these agents. Chlortetracycline has deleterious effects on human spermatozoa at concentrations of 100 mcg/mL,16 and minocycline hydrochloride has been found to be toxic to bovine spermatozoa at all concentrations tested (lowest was 50 mcg/mL).21 Tetracycline hydrochloride does not appear to affect the motility and viability of human spermatozoa at a concentration of 4 mcg/10 6 sperm but has not been evaluated to date at higher concentrations. Due to the widespread applicability of tetracyclines to infections involving the genitourinary tract, further information is necessary to delineate the negative effects of these agents on human spermatozoal function. Tetracyclines appear to have less severe adverse effects on spermatogenesis than some of the other classes of agents but are relatively toxic to ejaculated spermatozoa at the concentrations seen therapeutically in man. It is likely that the beneficial effects of treatment of men with an infectious etiology for infertility may actually reflect a balance between the beneficial effects of eradication of infection and pyospermia versus the probably temporary negative effects of tetracyclines on spermatozoal function. The judicious use of antibiotics may lead to further improvement in the results of treatment of men with genitourinary infections and infertility, particularly for those patients requiring long-term or chronic administration of antibiotics. For example, Toth and Lesser 34 reported that in patients with demonstrated Ureaplasma urealyticum infection, doxycycline rather than tetracycline should be the antibiotic of choice.
Tetracyclines have been shown to bind avidly to mammalian spermatozoa including human sperm. The strong adsorption of tetracyclines to the head portion of spermatozoa has been used clinically to study the acrosome reaction, the fusion of the plasma membrane, and acrosomal cap of spermatozoa that occurs after capacitation. 33 Despite similar mechanisms of antibacterial action, the effects of tetracyclines and aminoglycosides on spermatogenesis are markedly different. No information is available on humans; however, treatment of rats with oxytetracycline9 for an 8day period had a minimal effect on spermatogenesis as evaluated by histologic examination. Tetracycline hydrochloride administered to rats in either therapeutic or toxic doses demonstrated20 only a negligible disruption of spermatogenesis after a I-month treatment period as evaluated by histology. There was a slight decrease in spermatogenic index, number of spermatogonia per tubule, and RNA content in spermatogenic cells of the rat testes in this study. In distinct contrast to their relatively mild effects on spermatogenesis, several tetracyclines
Recently, significant literature has developed regarding the detrimental effects of one sulfa drug, sulfasalazine, on male fertility. Sulfasalazine is used in the treatment of inflammatory bowel disease and has been in clinical use since the 1940s. It is metabolized to a sulfa moiety, sulfapyridine, as well as 5-aminosalicylic acid and absorbed from the colon after oral administration. The active agent against the bowel disease is the salicylate; however, animal studies have demonstrated that the antifertility effect of sulfasalazine is most likely mediated by sulfapyridine. 22 ,35 The producers of sulfasalazine estimate that 50,000 men are currently being treated with this drug. 22 Despite this long period of administration to a significant number of patients,
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SULFA DRUGS
the first reports of oligospermia related to treatment with sulfasalazine did not appear in the medical literature until 1979. These first reports have been substantiated with several descriptions of the temporal relationship between sulfasalazine treatment and 01igospermia. 23-25 The effect of sulfasalazine on semen quality (oligospermia' poor sperm motility, and possibly morphological changes, i.e., nucleomalacia) appears to be independent of serum luteinizing hormone, follicle-stimulating hormone, prolactin, and testosterone levels 22 in these patients although this finding has been disputed. 36 The alterations in fertility of men treated with this drug also appear to be independent of general health or severity of inflammatory bowel disease as evidenced by rapid improvement of semen quality after discontinuation of the drug despite worsening of bowel symptoms. Reinstitution of sulfasalazine therapy in patients without symptoms has been shown by Cosentino et a1. 22 to result in deterioration of semen quality. The effects of sulfasalazine on semen parameters appear to be fully reversible. Many pregnancies have been reported in couples after the man has stopped taking the drug despite treatment for up to 11 years. The time course of full reversibility would be consistent with a toxic effect on the testis, probably early in the process of spermatogenesis. A possible secondary effect on later stages of spermiogenesis is implied by the partial response of semen parameters within 2 weeks after withdrawal of the drug. Inadequate information is available on testicular biopsies of men who have taken this drug to fully assess its effect on testicular histology. The toxicity of sulfasalazine may be unique to this agent because other sulfa drugs appear to be without significant effects on semen parameters in men. Sulfadiazene has been shown to have no effect on semen parameters after a 2-week course of administration to normal healthy volunteers.37 Patients treated with sulfanilamide in doses of 828 to 1,800 mg/d for 16 to 58 days showed no significant alterations in total sperm count or percentage oflive spermatozoa. 38 The combination drug co-trimoxazole (sulfamethoxazole and trimethoprim) was found to decrease the sperm count in 37% of 40 patients being treated for possible genitourinary infection after referral for infertility.26 However, 42% of these patients also demonstrated improvement in semen quality with treatment, so a strong relationship between this agent and impairment of sperm production cannot be made on the basis of this report. One Vol. 55, No.2, February 1991
study from Germany27 indicated a possible effect of co-trimoxazole on semen parameters in urologic and dermatologic patients. Forty-five patients underwent semen analysis before, during, and after 7 to 80 days of treatment with 160 mg of trimethoprim and 800 mg of sulfamethoxazole per day given orally. The adverse effects on total sperm number, sperm motility, and morphology were not seen during the treatment period but only 4 weeks after stopping the combination drug. No further followup of these patients was presented. Based on these two clinical studies of co-trimoxazole, at most only a possible influence of this agent on spermatogenesis could be inferred. Despite several studies in man and animals on the effects of sulfa drugs on spermatogenesis, marked adverse effects on spermatogenesis and fertility have so far been demonstrated only for sulfasalazine. Further investigation is required to define the adverse action of sulfasalazine on spermatogenesis. PENICILLINS
Many of the side effects seen in the human use of penicillins result from the formation of a proteinpenicillin hapten that may induce an antibody response in the treated patient, leading to an allergic type of response. Little is known of the effects of penicillins on human spermatogenesis, and most of the penicillins appear to have minimal effects on spermatozoal function in vitro, as measured by· sperm motility and fertility. In rats, therapeutic doses of penicillin G and cephalothin (Keflin, Eli Lilly Co., Indianapolis, IN) have been found to cause spermatogenic arrest after treatment for 8 days with these agents. 9 Penicillin G,16 cephapirin, ceforanide, and ampicillin 39 have all been found to have minimal effects on mammalian spermatozoa. An apparently speciesspecific decrease in fertilizing capacity and motility has been seen with chicken spermatozoa28 at an ampicillin concentration of only 6.2 mcg/mL. This effect is not seen in bulls17 or horses,39 but the effects of ampicillin on human spermatozoa have not been evaluated to date. Dicloxacillin has also been shown to decrease bull sperm motility at concentrations of antibiotic found in the urine (200 mcg/mL); however, this effect has not been reported in humans. The apparent relative safety of penicillins for spermatozoa has led to the widespread acceptance of the use of penicillin (frequently in combination Schlegel et al.
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with streptomycin, 1,000 IV /mL and 1,000 mcg/mL, respectively) as a semen extender for the cryopreservation of animal spermatozoa. MISCELLANEOUS
The effects, if any, on human spermatogenesis and sperm function are not known for most of the other antibiotics that have been evaluated in animals. Agents that affect DNA gyrase are ofparticular interest because of the emerging use of the quinolones, a class of antibiotics that inhibits the enzyme DNA gyrase, and is increasingly used for urologic patients. Nalidixic acid, which inhibits DNA gyrase and tRNA synthetases,4o has been found to have no effect in vitro on equine spermatozoa. IS Novobiocin, a similar antibiotic agent no longer in therapeutic use for humans, was found to be toxic in vitro to bovine spermatozoa at all concentrations tested (lowest was 125 mcg/mL)P It is interesting that the effect of novobiocin on DNA gyrase, also known as topoisomerase, is more pronounced for eukaryotic cells than is seen with nalidixic acid. However, because spermatozoa are not thought to actively transcribe DNA for protein synthesis, the mechanism of toxicity for novobiocin may be other than its effect on DNA gyrase. Ofloxacin is the only quinolone for which reproductive studies have been reported to date. Ofloxacin has been evaluated in adult male mice4I and found to have no adverse effect on germ cell chromosomes during 1 to 5 days of treatment. Clearly, further investigation is needed into the potential adverse effects on fertility of these agents that are likely to be used for suppressive therapy over long periods of time in increasing numbers of patients. DISCUSSION
At least some antibiotics from each ofthe classes of agents discussed above have been found to adversely affect male fertility potential in humans or in a carefully studied animal model. However, there is little information regarding the mechanisms by which these agents affect spermatogenesis or spermatozoal function. Future studies will need to clarify and examine the following questions. At what stage or stages in spermatogenic differentiation do antibiotics cause spermatogenic arrest? Are there species-specific differences in the effect of an antibiotic on spermatogenesis? By what biochemical mechanism does an antibiotic 240
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affect spermatogenesis, and if that mechanism differs from the antimicrobial action, how can it be prevented? For example, if the toxicity from sulfasalazine involves the inhibition of endogenous folic acid production in the testis, which is thought to be minimal in other eukaryotic cells, can that effect be altered by administration of high dose folic acid to these patients? Are the effects of antibiotics on spermatogenesis seen only during treatment, as is currently believed, or are there permanent changes in the number of stem cells in the testis? Finally, the clinical implications of the questions raised in this review must be addressed. Is there an optimal antibiotic agent or class of antibiotics to use against susceptible microbes for long-term suppressive therapy in the male urologic patient desiring fertility? Should particular agents, such as minocycline and other tetracyclines, not be used in any male patient with infertility because of their toxic effects on spermatozoal function? Antibiotics appear to affect spermatogenesis by causing spermatogenic arrest in germ cells not protected from these agents by the blood-testis barrier. Clinical observation of patients requiring long-term suppressive use of antibiotics (e.g., adult vesicoureteral reflux patients) may provide further information regarding the adverse effects of antibiotics in man with minimal confounding effects from underlying disease processes. Clearly, treatment of patients with acute bacterial infections requires the use of antibiotics that reach the site of infection and are effective against the organism to be eradicated. Furthermore, the effects of any illness on fertility potential have to be taken into account when evaluating adverse effects of antibiotics on male fertility. However, based on the accumulating knowledge of antibiotic effects on spermatogenesis and spermatozoal function in many different species, including man, we . must consider that there is likely to be a detrimental effect of antibiotics on male fertility potential at least during the course of treatment. A patient with pyospermia requires treatment for his infection. To minimize the potentially detrimental effects of antibiotics, treatment should await results of semen culture. The antibiotic with demonstrated in vitro effectiveness and the minimum possible detrimental effects on fertility may then be used for treatment of infection. Based on the data available, it is possible that the tetracyclines may adversely affect spermatozoal function. The infertile patient with genitourinary infections may be better managed by treatFertility and Sterility
ment of susceptible organisms with penicillin derivatives (cephalosporins). Penicillin derivatives appear to have the least toxicity to male fertility potential of the available effective agents although their possible effects on human spermatogenesis have not been documented in detail. Further definition of the mechanism by which antibiotics affect spermatogenesis, the reversibility of these effects, the relative effects of different antibiotic agents on male fertility, and the exact exposure of spermatozoa to antibiotics inside the blood-testis barrier is necessary. This information will allow clinicians to better formulate a rational basis for the management of all patients, particularly men who are considered to be infertile or require long-term treatment with antibiotics. Further delineation of the mechanisms by which antibiotics adversely affect spermatogenesis, if pursued, may also facilitate the development of nonhormonal male contraceptive agents. Most importantly, clinicians must consider that antibiotics may represent agents with potential adverse effects on male fertility. It should be remembered that sulfasalazine was in widespread use for over 40 years in many patients before an association with infertility was recognized. One of the best sources for information regarding the adverse effects of any agent on human fertility remains thoughtful clinical observation.
state of knowledge regarding the adverse effects of antibiotics on male fertility is presented in this review. Acknowledgment. The authors thank Marc Goldstein, M.D., The New York Hospital-Cornell Medical Center, New York, New York, for his thoughtful review ofthis manuscript.
REFERENCES
Individual agents within each of the major classes of antibiotics have been shown to have significant adverse effects on spermatogenesis or spermatozoal function in mammals. For humans, infertility or significant alterations in semen parameters have been well documented for the nitrofurans and for patients on sulfasalazine. Other commonly used antibiotics, such as minocycline, have been shown to be toxic to sperm at any concentration. Until further information is available, clinicians must keep in mind that treatment with antibiotics may adversely affect the fertility potential of men. It is possible that some classes of antibiotic agents, such as the penicillins or the quinolones, may have minimal effects on male fertility and maintain the clinical efficacy for patients requiring long-term antibiotic suppressive therapy. Further investigation is needed into the relative toxicity of antibiotics and the mechanisms by which antibiotics affect spermatogenesis and spermatozoal function. A background of the current
1. Damewood MD, Grochow LB: Prospects for fertility after chemotherapy or radiation for neoplastic disease. Fertil Steril 45:443, 1986 2. Lipshultz LI, Howards SS: Evaluation of the subfertile man. Sem UroI2:73, 1984 3. Leto S, Frensilli FJ: Changing parameters of donor semen. Fertil Steril 36:766, 1981 4. Nelson CMK, Bunge RG: Semen analysis: Evidence for changing parameters of male fertility potential. Fertil Steril 25:503, 1974 5. Collins JA, Wrixon W, Jones LB, Wilson EH: Treatmentindependent pregnancy among infertile couples. N Engl J Med 309:1201, 1983 6. Paul MF, Paul HE, Kopko F, Bryson MJ, Harrington C: Inhibition by furacin of citrate formation in testis preparations. J BioI Chem 206:491, 1954 7. Politano VA, Leadbetter GW, Leadbetter WF: Use of furacin in treatment of testicular tumors: a case report. J Urol 79:771, 1958 8. Nelson WO, Bunge RG: The effect of therapeutic dosages of nitrofurantoin (furadantin) upon spermatogenesis in man. J Urol 77:275, 1957 9. Timmermans L: Influence of antibiotics on spermatogenesis. J Urol112:348, 1974 10. Nelson WO, Steinberger E: The effect of furadroxyl upon the testis of the rat. Anat Rec 112:367, 1952 11. Yunda IF, Kushniruk YI: Effect of nitrofuran preparations on spermatogenesis. Bull Exp BioI Med 77:68,1974 12. Karol HJ: Nitrofurans in treatment of malignant testicular tumors. J Urol84:120, 1960 13. Johnson RH, Rozanis J: A review of chemotherapeutic plaque control. Oral Surg Oral Med Oral Pathol 47:136, 1979 14. Furio MM, Wordell CJ: Treatment of infectious complications of acquired immunodeficiency syndrome. Clin Pharm 4:539,1985 15. Lastikka L, Virsu ML, Halkka 0, Eriksson K, Estola T: Goniomitosis in rats affected by mycoplasma or macrolides. Med BioI Eng Comput 54:146, 1976 16. White IG: The toxicity of some antibacterials for bull, ram, rabbit and human spermatozoa. Aust J Exp BioI Med Sci 32:41,1954 17. Berndtson WE, Foote RH: Survival and fertility of antibiotic-treated bovine spermatozoa. J Dairy Sci 59:2130, 1976 18. Back DG, Pickett BW, Voss JL, Seidel GE: Effect of antibacterial agents on the motility of stallion spermatozoa at various storage times, temperatures and dilution ratios. J Anim Sci 41:137,1975 19. Yunda IF, Kushniruk YI: Neomycin effect on testicle function. Antibiot Med BiotekhnoI18:43, 1973 20. Kushniruk YI: Influence of certain antibacterial prepara-
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SUMMARY
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21.
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23. 24.
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28.
29.
30.
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31. Ahmad K, Foote RH: Motility and fertility of frozen bull spermatozoa in tris-yolk and milk extenders containing amikacin sulfate. J Dairy Sci 68:2083, 1985 32. Sexton T J, Jacobs LA, McDaniel G R: A new poultry extender. 4. Effects of antibacterials in control of bacterial contamination in chicken semen. Poult Sci 59:274,1980 33. Ericsson RJ, Baker VF: Binding of tetracycline to mammalian spermatozoa. Nature 214:403, 1967 34. Toth A, Lesser ML: Ureaplasma urealyticum and infertility: the effect of different antibiotic regimens on the semen quality. J UrolI28:705, 1982 35. O'Morain CO, Smethurst P, Dore CJ, Levi AJ: Reversible male infertility due to sulphasalazine: studies in man and rat. Gut 25:1078, 1985 36. Ragni G, Bianchi Porro G, Ruspa M, Barattini G, Lombardi C, Petrillo M: Abnormal semen quality and low serum testosterone in men with inflammatory bowel disease treated for a long time with sulfasalazine. Andrologia, 16: 162,1984 37. Osenkop RS, MacLeod J: Sulfadiazene: its effect on spermatogenesis and its excretion in the ejaculate. J Urol58:80, 1947 38. Heckel NJ, Hori CG: The effect of sulphanilamide upon spermatogenesis in Man. Am J Med Sci 198:347, 1939 39. Timoney PJ, O'Reilly PJ, Harrington AM, McCormack R, McArdle JF: Survival of haemophilus equigenitalis in different antibiotic-containing semen extenders. J Reprod Fertil27(suppl):377, 1979 40. Wright HT, Nurse KC, Goldstein DJ: Nalidixic acid, oxolinic acid, and novobiocin inhibit yeast glycyl and leucyltransfer RNA synthetases. Science 213:455, 1981 41. Shimada H, Ebine Y, Sato T, Kurosawa Y, Arauchi T: Dominant lethal study in male mice treated with ofloxacin, a new antimicrobial drug. Mutat Res 144:51, 1985
Received March 23, 1990. Dr. Schlegel is an American Foundation for Urologic Diseases Fellow and was supported in part by grant 2 T32 DK 07313-11 from the National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland. He is affiliated with The Population Council, Center for Biomedical Research and the Department of Surgery/U rology, The N ew York Hospital-Cornell Medical Center, New York, New York. Reprint requests: Peter N. Schlegel, M.D., The Population Council, Center for Biomedical Research, Rockefeller University, 1230 York Avenue, Box 273, New York, New York 10021. Drs. Chang and Marshall are affiliated with the James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland. "
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