Pharmacology and Therapeutics
Topical Metronidazole Gel Use in Acne Vulgaris p. Gamborg Nielsen, M.D.
Abstract: Two percent metronidazole and 5% benzoyi peroxide cream was evaluated in four clinical trials. It could be shown that this test cream was significantly better than 5% benzoyi peroxide jelly alone, and significantly better than a placebo cream. It was also shown that 2% metronidazole and 5% benzoyi peroxide cream was equal to systemic oxytetracycline therapy. The advisability of the combination of metronidazole and benzoyi peroxide was simultaneously discussed.
The efficacy of antifungal imidazole derivatives in acne vulgaris was first reported in 1978. The eflfect was associated with follicular infestation by Pityrosporon ovale, and was generally related to long-term antibiotic therapy. ' It was also shown that antifungal imidazoles have a bactericidal eflect on gram-positive cocci.^ The usefulness of miconazole for acne vulgaris was indicated in the early 1980s, and it was shown that a combination of 2% miconazole and 5% benzoyi peroxide improved this effect.^ At the same time, it was documented that topical metronidazole for rosacea was superior to placebo and equal to systemic oxytetracycline therapy.'*'' Microorganisms found in rosacea lesions were not sensitive to metronidazole,* and it was proved that metronidazole impedes leukocyte chemotaxis and selectively suppresses some aspects of cell-mediated immunity.^'* Consequently, it was supposed that metronidazole, in addition to its antimicrobial activity, had an anti-inflammatory effect. Apart from Demodexfolliculorum, the same microorganisms found in rosacea lesions are found in those of acne, and due to its anti-inflammatory effect, it was
From the Department of Dermatology, Varberg Hospital, Varberg, Sweden. Supported by A/S Dumex, Ltd., Copenhagen, Denmark. Address correspondence to: P. Gamborg Nielsen, M.D., Department of Dermatology, Varberg Hospital, S-432 81 Varberg, Sweden.
662
expected that metronidazole would have an eflect on acne vulgaris. However, clinical trials proved that the eflect of 1 % metronidazole cream did not significantly difler from that of placebo cream.* Based on experiences from treatment of rosacea and acne vulgaris, it was considered to be of interest to study the efficacy of a combination of 2% metronidazole and 5% benzoyi peroxide on acne lesions. Materials and Methods • Clinical trials were performed from 1983 to 1987 in four groups of patients suffering from acne vulgaris, grades II to III, according to the four-category acne classification of Pillsbury, Shelley, and Kligman.'° The studies took place at a dermatologic department during the winter months, and the patients had not been treated with agents active against acne during the 3 months preceding the start of the trials. Test coinpositions were applied to the face, limited by the hair border and the mandibular arch, twice-daily for 6 weeks. The test cream base was an oil-in-water emulsion (propylene glycol 15.0%, cetylanum 5.0%, cetanol 15.0%, sodium lauryl sulfate 0.8%, and citric aeid disodium hydrogen phosphate buffer [pH 3.4] 65.0%). Apart from thefirstgroup, in which patients were provided with 100 g of the test cream, all patients were supplied with 75 g of test cream. The patients were not allowed to use any other acne treatment during the trial. The final examination, performed after 6 weeks of treatment, included clinical assessment, lesion counts (papules, pustules, and cysts), standardized photography, and the patient's subjective opinion of the treatment's effect. The objective clinical assessment was expressed in four categories, as was the photographic evaluation, which was performed by two independent dermatologists. Papules, pustules, and eysts were counted at entry and at the end of the studies. Comedones were not counted. The patient's subjective opinion of the treatment result was classed as much improved, improved, somewhat improved, unchanged, worse, or much worse. Before the study, 100 patch tests (50 2% metronidazole and 5% benzoyi peroxide cream, and 50 cream base)
September 1991, Vol. 30, No. 9
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Topical Metronidazole and Acne Vulgaris • Nielsen
were performed, and at the end, all patients were tested with 2% metronidazole and 5% benzoyi peroxide cream using the method recommended by the International Contact Dermatitis Research Group (ICDRG). Percutaneous absorption of metronidazole was determined by the HFLC method, first described by Hackett and Dusci." The determination of metronidazole efficacy included 53 patients derived from groups 2 and 3 treated with 2% metronidazole and 5% benzoyi peroxide eream, with 20 patients from group 2 treated with placebo cream serving as controls. Side effects were registered, and for statistical calculations of means, the student's t-test was used.
Group 1 • Eighteen military conscripts (18 men and 0 women), with an average age of 19 years (age range, 17-20 years), entered an open trial of 2% metronidazole and 5% benzoyi peroxide prepared in the test cream base. The patients constituted a highly uniform group with regard to diet and environment. At entry and at the end of the study, the patients were examined in Wood's light for coral red and yellow fluorescence.
Group 2 • Forty-three randomly selected patients with acne vulgaris (24 women and 19 men), with an average age of 19 years (age range, 17-31 years), entered the study. The trial was performed in a double-blind fashion, using 2% metronidazole and 5% benzoyi peroxide cream versus placebo cream. The average amount of cream applied to the face during the study period was 39.8 g (range, 24.671.9 g). The mean amount of metronidazole applied by each patient was 6.58 mg/d (range, 4.46-12.3 mg/d). Patients were randomly assigned to one of the two courses of treatment. Twenty-three were allocated to 2 % metronidazole and 5% benzoyi peroxide cream, whereas 20 received the cream base. Group 3 • Sixty randomly elected patients (33 women and 27 men), with an average age of 24 years (age range, 15-42 years), were enlisted in the trial. Patients were randomly assigned to one of the two courses of treatment. Thirty were allocated to 2% metronidazole and 5% benzoyi peroxide cream, and 30 to 5% benzoyi peroxide jelly. The test cream was the same, and the reference composition with cosmetic and galenical properties similar to those of the test cream. The average amount of cream and jelly applied to the face during the study was 43.8 g (range, 11.9-73.7 g). Group 4 • Fifty-two randomly selected patients (30 women and 22 men), with an average age of 26 years (age range, 17-39 years), were included in the study. Twenty-six were allocated to 2% metronidazole and 5% benzoyi peroxide cream and placebo tablets, and 26 to oxytetracycline tablets 250 mg twice daily and placebo cream. The average
663
amount of cream applied to the face during the study period was 28.5 g (range, 8.5-70.8 g). Tablets were taken twice daily, 30 tninutes before meals. Results
No allergic reactions were observed in the 100 dermatologic outpatients tested with 2% metronidazole and 5% benzoyi peroxide cream or the cream base, but irritant reactions were found in 10%. All patients included in group 1 completed the study. Coral red fluorescence was found in eight (44.4%), and yellowfluorescencein six (33.3%) patients at entry to the trial. No fluorescence at all was found at the close of the study. The reduction of papules and pustules was about 70%, but the number of cysts at entry was too few for assessment. The objective and photographic assessments and the patients' subjective opinions of treatment effect corresponded well with each other (Table 1). In group 2, it was found that 2% metronidazole and 5% benzoyi peroxide cream was significantly more effective than placebo cream on papules and pustules (p < 0.05). These results were also confirmed in objective and photographic assessments, as well as by the patients' subjective opinions of treatment result. In group 3, 30 patients receiving the test cream and 29 receiving 5% benzoyi peroxide jelly completed the study. One patient treated with 5% benzoyi peroxide jelly left the study due to insufficient eflfect. The results of the overall clinical and photographic assessment showed a significant diflerence between the two courses of treatment, with the test cream being statistically superior Xc 5% benzoyi peroxide jelly (Table 1). The reduction of papules was significantly greater in the test cream group (p < 0.05), but no significant diflerence in the number of pustules was registered. The number of cysts was too few for any conclusions. The patients' subjective opinions of the treatment eflect favored the test eream, and this diflerence was statistically significant (p < 0.05) (Table 1). In group 4, 23 patients receiving 2% metronidazole and 5% benzoyi peroxide cream, and 23 receiving oxytetracycline completed the study. Two patients became pregnant during the study period and one patient was breast-feeding. These patients stopped treatment and were excluded from the trial. Three patients left the country during the study period. Of those patients who did not complete the tdal, three came from the test cream group and three from the oxytetracycline group. The results of the clinical assessment and photographic evaluation showed no significant diflerence between the two courses of treatment (Table 1). The reduction
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International Journal of Dermatology • September 1991
Vol. 30
Table 1. Objective and Photographic Assessment Gradedin Four Categories and Subjective Opinion of Treatment Effect Classified in Six Categories (Expressed in Number of Patients; Belonging to Groups 1-4) Groups Group 2 (n = 43)
Objective assessment 0-25% 26-50% 51-75% 76-100% Photographic assessment 0-25% 26-50% 51-75% 76-100% Subjective opinion Much improved Improved Somewhat improved Unchanged Worse Much worse
Group 3 (n = 60)
Group 4 (n = 52)
1-4
(n = 94)
Test (n = 30)
BPO (n = 29)
Test (n = 23)
Tetracycl (n = 23)
Test (n = 94)
9 3 8 0
2 2 8 18
9 3 3 14
1 2 8 12
2 4 6 11
7 7 26 54
2 5 5 11
10 4 6 0
3 4 4 19
8 2 3 16
1 3 10 9
3 4 4 12
8 13 22 51
15 4 3 1 0 0
2 6 1 11 0 0
18 7 1 4 0 0
13 4 4 8 0
12 8 2 1 0 0
9 6 4 3 1
54 26 7 7 0 0
Group 1 (n = 18)
Test (n = 23)
1 1 4 12
2 6 12
3
2 1 3 12 9 7 I 1 0 0
Placebo (n = 20)
0
0
Test: 2% metronidazole and 5% benzoyi peroxide cream; BPO: benzoyi peroxide 5% jelly; Tetracycl: oxytetracycline.
of papules was the same in both groups, but the reduction of pustules was significantly greater in patients treated with the test cream (p < 0.05). Even though significant figures were obtained, the material was too small for any definite conclusions. In groups 1 through 4, 94 patients were treated with 2% metronidazole and 5% benzoyi peroxide cream. At the objective clinical assessment, 85.1% of the patients were improved by 51% to 100%, and at the photographic evaluation 11.1%; likewise 85.1% of the patients considered themselves improved or much improved. Papules were reduced by 75.1%, pustules by 58.3%, and cysts by 36.4%. Due to limited number, the eflicacy of the test cream on pustules and cysts was difficult to evaluate. Stinging was experienced by only one patient in the test cream groups. However, dryness of facial skin was a common phenomenon during the first 2 weeks of the treatment period, but this decreased during the following weeks, and had no influence on the treatment results. Such dryness is generally found among patients treated with preparations containing benzoyi peroxide. No allergic reactions were registered. At the final patch test, 18 (19%) irritant reactions were found among those who had used 2% metronida-
zole and 5% benzoyi peroxide cream. Of those patients who had used 5% benzoyi peroxide, nine (31%) irritant reactions were registered. Two (10%) irritant reactions were found in those patients who had used placebo cream (cream base). Determination of metronidazole in serum showed only traces of metronidazole or substances interfering with the analysis. Results ranged from 15-68 ng/ml serum, corresponding to a sensitivity limit of the method used of 50 ng/ml serum. Serum values exceeding the sensitivity limit were found infivepatients, and traces of metronidazole were found even in three patients treated with the placebo cream (control group), corresponding to analysis of pooled donor serum, in which a chromatographic pattern similar to metronidazole's is occasionally found. Discussion Without a doubt, 2% metronidazole and 5% benzoyi peroxide cream is an eflective treatment for the papulopustulous stage of acne vulgaris. The test cream was shown to be significantly superior to placebo cream and to 5% benzoyi peroxide jefly alone. Furthermore, it was equal to systemic oxytetracycline therapy, at least
No. 9
Topical Metronidazole and Acne Vulgaris • Nielsen
for the milder types of acne vulgaris. For severe cases of papulo-pustulous acne, systemic treatment is preferred. Two percent metronidazole and 5% benzoyi peroxide cream appeared most effective in women over 20 years of age. This finding raises the question of whether or not intermediate forms of acne vulgaris and rosacea exist, or if they may simply be interpreted as a differential diagnostic problem. Three ingredients with activity against acne vulgaris were included in the test cream: metronidazole, benzoyi peroxide, and propylene glycol. It has previously been documented that metronidazole possesses an anti-inflammatory effect through impeding leukocyte chemotaxis.'^''' Susceptibility of cutaneous propionibacteria to metronidazole has not been proved, and its effect on acne vulgaris therefore probably depends on its anti-inflammatory action.'" Benzoyi peroxide is a substance with a well-documented bacteriostatic effect on cutaneous propionibacteria, and it has the ability to decrease hydrolysis of triglycerides.'^ Propylene glycol has a keratolytic effect, and is generally used as an enhancer for active substances included in creams and ointments. It has recently been shown that 15% propylene glycol in distilled water has a fungicidic effect on P. ovale.^^ Theoretically, these three substances included in the test cream may have an additive effect on factors known to induce acne lesions. However, none has any influence on the etiologic background. Propylene glycol probably enhances the percutaneous penetration of metronidazole without a simultaneous increase in serum levels, compared to a metronidazole cream without this additive. Acne lesions are generally located deeper in the skin than those of rosacea, and, therefore, enhancement of percutaneous penetration of metronidazole was intended. Based on several experimental studies, there are reservations as to the use of a combination of metronidazole and benzoyi peroxide. The reductive metabolism of the nitro group of metronidazole has been shown to be responsible for its mutagenic and carcinogenic properties. Nitro-reductases are active only in anaerobic environments, and have never been found in human cells, probably due to generally good oxygenation.'^ Anaerobic conditions do not exist in dermal cells of normal individuals or in patients with non-necrotic acne vulgaris and rosacea. Therefore, reductive metabolism in those cells may be considered inconceivable. Reduction of the nitro group does not occur in bacteria or fungi unsusceptible to metronidazole, as reduction is a condition of the drug's antimicrobial activity. Metronidazole is most likely absorbed as it is, undergoing an oxidative biotransforma-
665
tion in the liver and being excreted as metronidazole or its oxidative metabolites in the urine. During the last decades, benzoyi peroxide has been prescribed for mild acne vulgaris, and it is currently the most common topically applied substance. In previously performed studies, free radical-generating capacity and enhancement of malignant conversion of benign skin tumors due to topically applied benzoyi peroxide have been documented.'* It has been emphasized that the rate of malignant conversion is faster in ultraviolet (UV)-induced tumors, but it has also been shown that benzoyi peroxide protects against tumorigenicity and does not enhance carcinogenicity in this type of tumor, whereas benzoyi peroxide without doubt enhances chemical carcinogenesis."'^° Topically applied benzoyi peroxide has been shown to be absorbed in considerable amounts, and later split in the epidermis into benzoic acid and oxygen. Therefore, an anaerobic environment, which is a prerequisite of reduction of the nitro group of metronidazole, may be considered unlikely due to liberation of oxygen. Benzoyi peroxide initiates free radical reactivity of the nitroimidazoles, and this effect is significantly enhanced by irradiation with UV light near their absorption maximum of 320 to 325 nm. The time scale of the irradiation is believed to fall in the range of microseconds to milliseconds.^' However, oxygen has been documented to be an efficient inhibitor of this process.^^ Chemical initiation of free radical reactivity of metronidazole by benzoyi peroxide appears to be the most important objection against using this test cream. The reductive metabolism of metronidazole may be considered rather unlikely, due to chemical and physiologic oxygenation. Even though it would be desirable to abolish carcinogenic aspects of these compounds, investigations into their mutual reactivity and interaction should also be performed. Until its side effects have been properly elucidated, this test cream should be used with caution.
References 1. Aron-Brunetiere R, Avram A. Pityrosporum ovale and acne vulgaris. Mykosen. I978;(Suppl):l50-I54. 2. Cartwright RY. Pharmacology of imidazole derivatives with anti-mycotic activity. Mykosen. 1978(Suppl):298-303. 3. Degrect H, Van den Borsche G. Double blind evaluation of a mico-nazole-benzoyl peroxide combination for the topical treatment of acne vulgaris. Dermatologica. 1982; 164:201-208. 4. Gamborg Nielsen P. Treatment of rosacea with 1% metronidazole cream: A double-blind study. Br J Dermatol. 1983; 108:327332.
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5. Gamborg Nielsen P. A double blind study of 1% metronidazole cream versus oxytetracycline therapy for rosacea. Br J Dermatol 1983;109:63-65. 6. Eriksson G, Nord CE. Impact of topical metronidazole of the skin and colon microflora in patients with rosacea. Infection 1987;1:8-1O. 7. Gnarpe H, Persson S, Belsheim J. Influence of metronidazole and tinidazole on leukocyte chemotaxis in Crohn's disease. Infection. 1978 ;(Suppl): 107-109. 8. Grove DI, Mahmoud AAF, Warren KS. Suppression of cell mediated immunity by metronidazole. Int Arch Allergy Appl Immunol. 1977;54:422-427. 9. Gamborg Nielsen P. Treatment of Acne Vulgaris with 1 % Metronidazole Cream. Copenhagen, Denmark: Dumex, Ltd., 1984. 10. Pillsbury DM, Shelley MB, Kligman AM. A Manual of Cutaneous Medicine. Philadelphia: WB Saunders, 1961:223-276. 11. Hackett LP, Dusci LJ. Determination of metronidazole and tinidazole in human plasma using high-performance liquid chromatography. J Chromatogr. 1979; 175:347-349. 12 Plewig G, Schopf E. Anti-inflammatory eifects of antimicrobial agents: An in vivo study. J Invest Dermatol. 1975;65:532-536. 13 Esterley N, Furey N, Flanagan L. The effect of antimicrobial agents on leucocyte chemotaxis. J Invest Dermatol. 1978-7O-5155.
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14. Hoffler U, Niederau W, Pulverer G. Susceptibility of cutaneous
15.
16 17. 18
19. 20. 21. 22
propionibacteria to newer antibiotics. Chemotherapy 198026:7-11. Fulton JE, Farzad-Bakshandeh A, Bradley S. Studies of the mechanism of action of topical benzoyi peroxide and vitamin A acid in acne vulgaris. J Cutan Pathol. 1974; 1:191-200. Faergeman J, Fredriksson T. Propylene glycol in the treattnent of tinea versicolor. Acta Derm Venereol (Stockh). 1980;60:92-93. Olsen PR, Hebjorn M. Safety of metronidazole? Arch Pharm Chem Sci Ed. 1982;10:69-79. Slaga T, Klein-Szanto AJP, Triplett LL, et al. Skin tumor-promoting activity of benzoyi peroxide, a widely used free radical generating compound. Science. 1981;213:1023-1025. Iversen OH. Carcinogenesis studies with benzoyi peroxide (panoxyl gel 5%). J Invest Dermatol. 1986;4:442-448. Kelin-Szanto AJP, Slaga TJ. Effects of peroxides on rodent skin: Epidermal hyperplasia and tumor promotion. J Invest Dermatol. I982;79:30-34. Epstein JH. The effects of benzoyi peroxide (BPO) and croton oil (CO) on UVB initiated carcinogenesis. Photoehem Photobiol. 1983;37(Suppl):538-543. Moore DE. Reactions of nitroimidazoles with free radicals: Enhancement of reaction by UV-irradiation. Int J Radiat Biol 1985;5:563-568.
A laboratory of bacteriology in the last few years of the 19th century. It contains 240 original objects. From the Fundaci6Museu d'Histdria de la Medicina (Barcelona). Submitted by Felipe Cid, M.D., Barcelona, Spain.
Topical Metronidazole Gel Use in Acne Vulgaris p. Gamborg Nielsen, M.D.
Abstract: Two percent metronidazole and 5% benzoyi peroxide cream was evaluated in four clinical trials. It could be shown that this test cream was significantly better than 5% benzoyi peroxide jelly alone, and significantly better than a placebo cream. It was also shown that 2% metronidazole and 5% benzoyi peroxide cream was equal to systemic oxytetracycline therapy. The advisability of the combination of metronidazole and benzoyi peroxide was simultaneously discussed.
The efficacy of antifungal imidazole derivatives in acne vulgaris was first reported in 1978. The eflfect was associated with follicular infestation by Pityrosporon ovale, and was generally related to long-term antibiotic therapy. ' It was also shown that antifungal imidazoles have a bactericidal eflect on gram-positive cocci.^ The usefulness of miconazole for acne vulgaris was indicated in the early 1980s, and it was shown that a combination of 2% miconazole and 5% benzoyi peroxide improved this effect.^ At the same time, it was documented that topical metronidazole for rosacea was superior to placebo and equal to systemic oxytetracycline therapy.'*'' Microorganisms found in rosacea lesions were not sensitive to metronidazole,* and it was proved that metronidazole impedes leukocyte chemotaxis and selectively suppresses some aspects of cell-mediated immunity.^'* Consequently, it was supposed that metronidazole, in addition to its antimicrobial activity, had an anti-inflammatory effect. Apart from Demodexfolliculorum, the same microorganisms found in rosacea lesions are found in those of acne, and due to its anti-inflammatory effect, it was
From the Department of Dermatology, Varberg Hospital, Varberg, Sweden. Supported by A/S Dumex, Ltd., Copenhagen, Denmark. Address correspondence to: P. Gamborg Nielsen, M.D., Department of Dermatology, Varberg Hospital, S-432 81 Varberg, Sweden.
662
expected that metronidazole would have an eflect on acne vulgaris. However, clinical trials proved that the eflect of 1 % metronidazole cream did not significantly difler from that of placebo cream.* Based on experiences from treatment of rosacea and acne vulgaris, it was considered to be of interest to study the efficacy of a combination of 2% metronidazole and 5% benzoyi peroxide on acne lesions. Materials and Methods • Clinical trials were performed from 1983 to 1987 in four groups of patients suffering from acne vulgaris, grades II to III, according to the four-category acne classification of Pillsbury, Shelley, and Kligman.'° The studies took place at a dermatologic department during the winter months, and the patients had not been treated with agents active against acne during the 3 months preceding the start of the trials. Test coinpositions were applied to the face, limited by the hair border and the mandibular arch, twice-daily for 6 weeks. The test cream base was an oil-in-water emulsion (propylene glycol 15.0%, cetylanum 5.0%, cetanol 15.0%, sodium lauryl sulfate 0.8%, and citric aeid disodium hydrogen phosphate buffer [pH 3.4] 65.0%). Apart from thefirstgroup, in which patients were provided with 100 g of the test cream, all patients were supplied with 75 g of test cream. The patients were not allowed to use any other acne treatment during the trial. The final examination, performed after 6 weeks of treatment, included clinical assessment, lesion counts (papules, pustules, and cysts), standardized photography, and the patient's subjective opinion of the treatment's effect. The objective clinical assessment was expressed in four categories, as was the photographic evaluation, which was performed by two independent dermatologists. Papules, pustules, and eysts were counted at entry and at the end of the studies. Comedones were not counted. The patient's subjective opinion of the treatment result was classed as much improved, improved, somewhat improved, unchanged, worse, or much worse. Before the study, 100 patch tests (50 2% metronidazole and 5% benzoyi peroxide cream, and 50 cream base)
September 1991, Vol. 30, No. 9
No. 9
Topical Metronidazole and Acne Vulgaris • Nielsen
were performed, and at the end, all patients were tested with 2% metronidazole and 5% benzoyi peroxide cream using the method recommended by the International Contact Dermatitis Research Group (ICDRG). Percutaneous absorption of metronidazole was determined by the HFLC method, first described by Hackett and Dusci." The determination of metronidazole efficacy included 53 patients derived from groups 2 and 3 treated with 2% metronidazole and 5% benzoyi peroxide eream, with 20 patients from group 2 treated with placebo cream serving as controls. Side effects were registered, and for statistical calculations of means, the student's t-test was used.
Group 1 • Eighteen military conscripts (18 men and 0 women), with an average age of 19 years (age range, 17-20 years), entered an open trial of 2% metronidazole and 5% benzoyi peroxide prepared in the test cream base. The patients constituted a highly uniform group with regard to diet and environment. At entry and at the end of the study, the patients were examined in Wood's light for coral red and yellow fluorescence.
Group 2 • Forty-three randomly selected patients with acne vulgaris (24 women and 19 men), with an average age of 19 years (age range, 17-31 years), entered the study. The trial was performed in a double-blind fashion, using 2% metronidazole and 5% benzoyi peroxide cream versus placebo cream. The average amount of cream applied to the face during the study period was 39.8 g (range, 24.671.9 g). The mean amount of metronidazole applied by each patient was 6.58 mg/d (range, 4.46-12.3 mg/d). Patients were randomly assigned to one of the two courses of treatment. Twenty-three were allocated to 2 % metronidazole and 5% benzoyi peroxide cream, whereas 20 received the cream base. Group 3 • Sixty randomly elected patients (33 women and 27 men), with an average age of 24 years (age range, 15-42 years), were enlisted in the trial. Patients were randomly assigned to one of the two courses of treatment. Thirty were allocated to 2% metronidazole and 5% benzoyi peroxide cream, and 30 to 5% benzoyi peroxide jelly. The test cream was the same, and the reference composition with cosmetic and galenical properties similar to those of the test cream. The average amount of cream and jelly applied to the face during the study was 43.8 g (range, 11.9-73.7 g). Group 4 • Fifty-two randomly selected patients (30 women and 22 men), with an average age of 26 years (age range, 17-39 years), were included in the study. Twenty-six were allocated to 2% metronidazole and 5% benzoyi peroxide cream and placebo tablets, and 26 to oxytetracycline tablets 250 mg twice daily and placebo cream. The average
663
amount of cream applied to the face during the study period was 28.5 g (range, 8.5-70.8 g). Tablets were taken twice daily, 30 tninutes before meals. Results
No allergic reactions were observed in the 100 dermatologic outpatients tested with 2% metronidazole and 5% benzoyi peroxide cream or the cream base, but irritant reactions were found in 10%. All patients included in group 1 completed the study. Coral red fluorescence was found in eight (44.4%), and yellowfluorescencein six (33.3%) patients at entry to the trial. No fluorescence at all was found at the close of the study. The reduction of papules and pustules was about 70%, but the number of cysts at entry was too few for assessment. The objective and photographic assessments and the patients' subjective opinions of treatment effect corresponded well with each other (Table 1). In group 2, it was found that 2% metronidazole and 5% benzoyi peroxide cream was significantly more effective than placebo cream on papules and pustules (p < 0.05). These results were also confirmed in objective and photographic assessments, as well as by the patients' subjective opinions of treatment result. In group 3, 30 patients receiving the test cream and 29 receiving 5% benzoyi peroxide jelly completed the study. One patient treated with 5% benzoyi peroxide jelly left the study due to insufficient eflfect. The results of the overall clinical and photographic assessment showed a significant diflerence between the two courses of treatment, with the test cream being statistically superior Xc 5% benzoyi peroxide jelly (Table 1). The reduction of papules was significantly greater in the test cream group (p < 0.05), but no significant diflerence in the number of pustules was registered. The number of cysts was too few for any conclusions. The patients' subjective opinions of the treatment eflect favored the test eream, and this diflerence was statistically significant (p < 0.05) (Table 1). In group 4, 23 patients receiving 2% metronidazole and 5% benzoyi peroxide cream, and 23 receiving oxytetracycline completed the study. Two patients became pregnant during the study period and one patient was breast-feeding. These patients stopped treatment and were excluded from the trial. Three patients left the country during the study period. Of those patients who did not complete the tdal, three came from the test cream group and three from the oxytetracycline group. The results of the clinical assessment and photographic evaluation showed no significant diflerence between the two courses of treatment (Table 1). The reduction
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International Journal of Dermatology • September 1991
Vol. 30
Table 1. Objective and Photographic Assessment Gradedin Four Categories and Subjective Opinion of Treatment Effect Classified in Six Categories (Expressed in Number of Patients; Belonging to Groups 1-4) Groups Group 2 (n = 43)
Objective assessment 0-25% 26-50% 51-75% 76-100% Photographic assessment 0-25% 26-50% 51-75% 76-100% Subjective opinion Much improved Improved Somewhat improved Unchanged Worse Much worse
Group 3 (n = 60)
Group 4 (n = 52)
1-4
(n = 94)
Test (n = 30)
BPO (n = 29)
Test (n = 23)
Tetracycl (n = 23)
Test (n = 94)
9 3 8 0
2 2 8 18
9 3 3 14
1 2 8 12
2 4 6 11
7 7 26 54
2 5 5 11
10 4 6 0
3 4 4 19
8 2 3 16
1 3 10 9
3 4 4 12
8 13 22 51
15 4 3 1 0 0
2 6 1 11 0 0
18 7 1 4 0 0
13 4 4 8 0
12 8 2 1 0 0
9 6 4 3 1
54 26 7 7 0 0
Group 1 (n = 18)
Test (n = 23)
1 1 4 12
2 6 12
3
2 1 3 12 9 7 I 1 0 0
Placebo (n = 20)
0
0
Test: 2% metronidazole and 5% benzoyi peroxide cream; BPO: benzoyi peroxide 5% jelly; Tetracycl: oxytetracycline.
of papules was the same in both groups, but the reduction of pustules was significantly greater in patients treated with the test cream (p < 0.05). Even though significant figures were obtained, the material was too small for any definite conclusions. In groups 1 through 4, 94 patients were treated with 2% metronidazole and 5% benzoyi peroxide cream. At the objective clinical assessment, 85.1% of the patients were improved by 51% to 100%, and at the photographic evaluation 11.1%; likewise 85.1% of the patients considered themselves improved or much improved. Papules were reduced by 75.1%, pustules by 58.3%, and cysts by 36.4%. Due to limited number, the eflicacy of the test cream on pustules and cysts was difficult to evaluate. Stinging was experienced by only one patient in the test cream groups. However, dryness of facial skin was a common phenomenon during the first 2 weeks of the treatment period, but this decreased during the following weeks, and had no influence on the treatment results. Such dryness is generally found among patients treated with preparations containing benzoyi peroxide. No allergic reactions were registered. At the final patch test, 18 (19%) irritant reactions were found among those who had used 2% metronida-
zole and 5% benzoyi peroxide cream. Of those patients who had used 5% benzoyi peroxide, nine (31%) irritant reactions were registered. Two (10%) irritant reactions were found in those patients who had used placebo cream (cream base). Determination of metronidazole in serum showed only traces of metronidazole or substances interfering with the analysis. Results ranged from 15-68 ng/ml serum, corresponding to a sensitivity limit of the method used of 50 ng/ml serum. Serum values exceeding the sensitivity limit were found infivepatients, and traces of metronidazole were found even in three patients treated with the placebo cream (control group), corresponding to analysis of pooled donor serum, in which a chromatographic pattern similar to metronidazole's is occasionally found. Discussion Without a doubt, 2% metronidazole and 5% benzoyi peroxide cream is an eflective treatment for the papulopustulous stage of acne vulgaris. The test cream was shown to be significantly superior to placebo cream and to 5% benzoyi peroxide jefly alone. Furthermore, it was equal to systemic oxytetracycline therapy, at least
No. 9
Topical Metronidazole and Acne Vulgaris • Nielsen
for the milder types of acne vulgaris. For severe cases of papulo-pustulous acne, systemic treatment is preferred. Two percent metronidazole and 5% benzoyi peroxide cream appeared most effective in women over 20 years of age. This finding raises the question of whether or not intermediate forms of acne vulgaris and rosacea exist, or if they may simply be interpreted as a differential diagnostic problem. Three ingredients with activity against acne vulgaris were included in the test cream: metronidazole, benzoyi peroxide, and propylene glycol. It has previously been documented that metronidazole possesses an anti-inflammatory effect through impeding leukocyte chemotaxis.'^''' Susceptibility of cutaneous propionibacteria to metronidazole has not been proved, and its effect on acne vulgaris therefore probably depends on its anti-inflammatory action.'" Benzoyi peroxide is a substance with a well-documented bacteriostatic effect on cutaneous propionibacteria, and it has the ability to decrease hydrolysis of triglycerides.'^ Propylene glycol has a keratolytic effect, and is generally used as an enhancer for active substances included in creams and ointments. It has recently been shown that 15% propylene glycol in distilled water has a fungicidic effect on P. ovale.^^ Theoretically, these three substances included in the test cream may have an additive effect on factors known to induce acne lesions. However, none has any influence on the etiologic background. Propylene glycol probably enhances the percutaneous penetration of metronidazole without a simultaneous increase in serum levels, compared to a metronidazole cream without this additive. Acne lesions are generally located deeper in the skin than those of rosacea, and, therefore, enhancement of percutaneous penetration of metronidazole was intended. Based on several experimental studies, there are reservations as to the use of a combination of metronidazole and benzoyi peroxide. The reductive metabolism of the nitro group of metronidazole has been shown to be responsible for its mutagenic and carcinogenic properties. Nitro-reductases are active only in anaerobic environments, and have never been found in human cells, probably due to generally good oxygenation.'^ Anaerobic conditions do not exist in dermal cells of normal individuals or in patients with non-necrotic acne vulgaris and rosacea. Therefore, reductive metabolism in those cells may be considered inconceivable. Reduction of the nitro group does not occur in bacteria or fungi unsusceptible to metronidazole, as reduction is a condition of the drug's antimicrobial activity. Metronidazole is most likely absorbed as it is, undergoing an oxidative biotransforma-
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tion in the liver and being excreted as metronidazole or its oxidative metabolites in the urine. During the last decades, benzoyi peroxide has been prescribed for mild acne vulgaris, and it is currently the most common topically applied substance. In previously performed studies, free radical-generating capacity and enhancement of malignant conversion of benign skin tumors due to topically applied benzoyi peroxide have been documented.'* It has been emphasized that the rate of malignant conversion is faster in ultraviolet (UV)-induced tumors, but it has also been shown that benzoyi peroxide protects against tumorigenicity and does not enhance carcinogenicity in this type of tumor, whereas benzoyi peroxide without doubt enhances chemical carcinogenesis."'^° Topically applied benzoyi peroxide has been shown to be absorbed in considerable amounts, and later split in the epidermis into benzoic acid and oxygen. Therefore, an anaerobic environment, which is a prerequisite of reduction of the nitro group of metronidazole, may be considered unlikely due to liberation of oxygen. Benzoyi peroxide initiates free radical reactivity of the nitroimidazoles, and this effect is significantly enhanced by irradiation with UV light near their absorption maximum of 320 to 325 nm. The time scale of the irradiation is believed to fall in the range of microseconds to milliseconds.^' However, oxygen has been documented to be an efficient inhibitor of this process.^^ Chemical initiation of free radical reactivity of metronidazole by benzoyi peroxide appears to be the most important objection against using this test cream. The reductive metabolism of metronidazole may be considered rather unlikely, due to chemical and physiologic oxygenation. Even though it would be desirable to abolish carcinogenic aspects of these compounds, investigations into their mutual reactivity and interaction should also be performed. Until its side effects have been properly elucidated, this test cream should be used with caution.
References 1. Aron-Brunetiere R, Avram A. Pityrosporum ovale and acne vulgaris. Mykosen. I978;(Suppl):l50-I54. 2. Cartwright RY. Pharmacology of imidazole derivatives with anti-mycotic activity. Mykosen. 1978(Suppl):298-303. 3. Degrect H, Van den Borsche G. Double blind evaluation of a mico-nazole-benzoyl peroxide combination for the topical treatment of acne vulgaris. Dermatologica. 1982; 164:201-208. 4. Gamborg Nielsen P. Treatment of rosacea with 1% metronidazole cream: A double-blind study. Br J Dermatol. 1983; 108:327332.
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5. Gamborg Nielsen P. A double blind study of 1% metronidazole cream versus oxytetracycline therapy for rosacea. Br J Dermatol 1983;109:63-65. 6. Eriksson G, Nord CE. Impact of topical metronidazole of the skin and colon microflora in patients with rosacea. Infection 1987;1:8-1O. 7. Gnarpe H, Persson S, Belsheim J. Influence of metronidazole and tinidazole on leukocyte chemotaxis in Crohn's disease. Infection. 1978 ;(Suppl): 107-109. 8. Grove DI, Mahmoud AAF, Warren KS. Suppression of cell mediated immunity by metronidazole. Int Arch Allergy Appl Immunol. 1977;54:422-427. 9. Gamborg Nielsen P. Treatment of Acne Vulgaris with 1 % Metronidazole Cream. Copenhagen, Denmark: Dumex, Ltd., 1984. 10. Pillsbury DM, Shelley MB, Kligman AM. A Manual of Cutaneous Medicine. Philadelphia: WB Saunders, 1961:223-276. 11. Hackett LP, Dusci LJ. Determination of metronidazole and tinidazole in human plasma using high-performance liquid chromatography. J Chromatogr. 1979; 175:347-349. 12 Plewig G, Schopf E. Anti-inflammatory eifects of antimicrobial agents: An in vivo study. J Invest Dermatol. 1975;65:532-536. 13 Esterley N, Furey N, Flanagan L. The effect of antimicrobial agents on leucocyte chemotaxis. J Invest Dermatol. 1978-7O-5155.
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14. Hoffler U, Niederau W, Pulverer G. Susceptibility of cutaneous
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propionibacteria to newer antibiotics. Chemotherapy 198026:7-11. Fulton JE, Farzad-Bakshandeh A, Bradley S. Studies of the mechanism of action of topical benzoyi peroxide and vitamin A acid in acne vulgaris. J Cutan Pathol. 1974; 1:191-200. Faergeman J, Fredriksson T. Propylene glycol in the treattnent of tinea versicolor. Acta Derm Venereol (Stockh). 1980;60:92-93. Olsen PR, Hebjorn M. Safety of metronidazole? Arch Pharm Chem Sci Ed. 1982;10:69-79. Slaga T, Klein-Szanto AJP, Triplett LL, et al. Skin tumor-promoting activity of benzoyi peroxide, a widely used free radical generating compound. Science. 1981;213:1023-1025. Iversen OH. Carcinogenesis studies with benzoyi peroxide (panoxyl gel 5%). J Invest Dermatol. 1986;4:442-448. Kelin-Szanto AJP, Slaga TJ. Effects of peroxides on rodent skin: Epidermal hyperplasia and tumor promotion. J Invest Dermatol. I982;79:30-34. Epstein JH. The effects of benzoyi peroxide (BPO) and croton oil (CO) on UVB initiated carcinogenesis. Photoehem Photobiol. 1983;37(Suppl):538-543. Moore DE. Reactions of nitroimidazoles with free radicals: Enhancement of reaction by UV-irradiation. Int J Radiat Biol 1985;5:563-568.
A laboratory of bacteriology in the last few years of the 19th century. It contains 240 original objects. From the Fundaci6Museu d'Histdria de la Medicina (Barcelona). Submitted by Felipe Cid, M.D., Barcelona, Spain.
