ADONIS 0 14O778391000324
J. net. Pharmncol. Therap. 14,257-262, 1991.
Pharmacokinetics of tinidazole in dogs and cats E. SARKIALA, A. JARVINEN*, S. V A L T T I L A t & M. M E R O Department of Clinical Sciences, College of Veterinary Medicine, Helsinki,* Department of Pharmacology and Toxicology, University of Helsinki, and t Orion Pharmaceutica, Analytical Department, Espoo, Finland
Sarkiala, E., Jgrvinen, A.. Valttila, S., Mero, M. Pharmacokinetics of tinidazole in dogs and cats. J. vet. P f u r m u v l . TIierup. 14, 257-262. Pharmacokinetics of tinidazole in dogs and cats after single intravenous (15 mg/ kg) and oral doses (15 mg/kg o r 30 mg/kg) were studied in a randomized crossover study. Tinidazole was completely absorbed at both oral dose levels in cats and dogs. Peak tinidazole concentration in plasma was 17.8 pg/ml in dogs and 22.5 pg/ml in cats after 15 mg/kg p.o. T h e oral dose of 30 rng/kg resulted in peak levels of 37.9 pg/ml in dogs and 33.6 pg/ml in cats. T h e apparent total plasma clearance of the d r u g was about twofold higher in dogs than in cats, resulting in an elimination half-life that was twice as long in cats (8.4 h) as in dogs (4.4 h). T h e apparent volume of distribution was 663 mVkg in dogs and 536 ml/ kg in cats. Therapeutic plasma drug concentrations higher than t h e M f C values of most tinidazole-sensitive bacteria were achieved for 24 h in cats and for 12 h in clogs after a single oral dose of 15 mg/kg. From the pharniacokinetic standpoint tinidazole seems to be well-suited to clinical use in small animal practice. Evu Sarkiuln, Drpnrtment vf Clinicul Scicmces, Cullegr vf Velrrinuty Midicine, Haviretilie, 57 00580 HeLsinki, Fiiclcnd.
INTRODUC’TION In the treatment of anaerobic o r mixed infections, a bacteriological diagnosis is seldom available at the time treatment is begun. Therefore, anti-microbial agents like chloramphenicol and clindamycin, which are effective against most anaerobes, are often preferred. However, since these agents can produce serious adverse effects their general use in infections that are not life-threatening can be questioned (Sande & Mandell, 1985;- Dow, 1988). Knowledge of the importance of anaerobic bacteria in infections like gingivitis and periodontitis also calls for the use of safer drugs in veterinary medicine (Mallonee et ul., 1988; Isogai et al., 1989). Several nitroimidazoles, like metronidazole and tinidazole, are widely used in humans, whereas only metronidazole has been used extensively in veterinary medicine. Nitroimi-
dazoles are bactericidal to most. Graninegative and also to many Gram-positive bacteria, including klactamase-producing Bric/rruidrs fragilis (Jokipii 8c Jokipii, 1977; Prescott & Baggot, 1988); they also have antiprotozoal activity (Webster, 1985). Moreover, they are known to have a wide therapeutic range and low toxicity. Tinidazole has been given in doses u p to 65 mg/kg to humans and 300 nig/kg to rats and monkeys without toxic or adverse reactions (Cossu el ul., 1986; Sawyer et al., 1976). Although nitroimidamles are generally well-tolerated they can cause gastrointestinal and cutaneous side-effects, thrombophlebitis after intravenous administration, headache, sleeplessness, depression, glossitis, stomatitis and dryness of the mucous membranes (Sawyer el ul., 1976: Andersson, 1981; Carmine et al., 1982; Webster, 1985). However, more serious adverse effects like neutropenia o r neurologic symptoms only 257
258 E . Sarkiula et al.
rarely occur, but prolonged high-dose therapy may be associated with carcinogenicity (Carmine et al., 1982; Webster, 1985). Tinidazole and metronidazole have been shown to be widely distributed in the body and to penetrate well into various tissues in man as well as in the dog and rat (Kimura el al., 1974; Anderson, 1981; Wood el ul., 1982). T h e total clearance of tinidazole in man is only about one-half of that of metronidazole resulting in a twofold longer elimination half-life and higher and more stable plasma concentrations compared with metronidazole (Welling & Monro, 1972; Mattie el al., 1982). Similarly, in horses the half-life of tinidazole was found to be 5.2 h and that of metronidazole 3.9 h (Prescott & Baggot, 1988; Pyorala et ul., 1990). T h e longer elimination half-life and the wide therapeutic range of tinidazole could be of advantage in veterinary medicine by allowing longer dosing intervals. Despite its obvious advantages over metronidazole, the pharmacokinetics of tinidazole has not been studied in cats and only one report exists on its pharmacokinetics in dogs (Kimura et al., 1974). T h e present study was undertaken to characterize the pharmacokinetics of tinidazole in dogs and cats after single intravenous (i.v.) and oral (p.0.) doses. To provide a basis for a rational dosage regimen in future studies and to test the linearity of the pharrnacokinetics of tinidazole two oral doses were used.
animal weight, was given. For the dogs the drug was hidden in a small piece of commercial dog food, while the cats received the drug together with 5 ml of water. For intravenous (i.v.) administration, tinidazole 5 mg/ml sohtion (Orion Pharmaceutica, Finland,. batch OCO42-1) was given as a bolus injection over 2 min.
Study design T h e study utilized a cross-over design. Each animal was given 15 mg/kg tinidazole both i.v. and p.0. and 30 mg/kg p.0. in a random order. A wash-out period of at least 2 weeks was allowed between the phases of the study. An indwelling plastic catheter was inserted in the cephalic vein of the dogs and in the jugular vein of the cats for collection of blood samples (4 ml each). T h e cats were sedated by giving an intramuscular (im.) injection of 80 yg/kg medetomidine (Farmos Group Ltd, Finland). After the catheter was inserted, the sedation was antagonized with atipamezole (32 pg/kg im.) (Farmos Group Ltd, Finland). Blood samples were taken immediately before and at 2, 4, 8, 16, 30 min and 1, 2, 4, 6, 12, 24, 48 h after i.v. administration and 0, 0.25, 0.5, 1, 1.5, 2, 3, 6, 8, 12, 24, 48 h after oral administration. All blood samples were taken in heparinized tubes. Plasma was separated by centrifugation and immediately deep frozen at -70 "C until assayed.
MATERIALS AND M E T H O D S Analytical methods AnimaLr and drugs
Six healthy Beagle dogs, four males and t w o females, were used. T h e dogs ranged in age from 4 to 5 years and in weight from 10.5 to 15.0 kg (mean 12.1 kg). In addition, six domestic shorthair cats (three males and three females) w e r e used. Their age ranged between 1 and 2 years and their weight from 2.4 to 3.7 kg (mean 2.8 kg). All animals were fasted over-night but water was freely accessible before the study. Tinidazole tablets (150 mg or 500 mg; Orion Pharmaceutica, Finland, batch OD 1-3 and NC 1-6, respectively) were divided and a piece of tablet, adjusted according to the
Concentrations of tinidazole in plasma samples were determined by high-performance liquid chromatography (HPLC) with UV detection at 313 nm. T h e method involved extraction of the plasma samples (0.2 ml) with 3 ml of dichloromethane. T h e organic phase was evaporated to dryness and dissolved into 200 y1 of the mobile phase and an aliquot of 20 ~1 was analysed by HPLC. T h e method was validated with regard to linearity, accuracy, precision, recovery and specificity. T h e method gave interferencefree and linear results over the concentration range 0.10-45.45 pg/ml. T h e recovery was more than 99% at all concentration levels
Plurmucokinetics of liniduzole
studied. T h e relative standard deviation of quality control samples 22.73 and 5.68 Fg/ml of tinidazole were 5.0 and 6.0% (n = 19), respectively. T h e precision of six successively analysed spiked plasma samples at the concentrations of 45.45, 13.64, 1.36 and 0.10 pg/ml of tinidazole were 1.8, 1.3, 1.7, and 1.2%, respectively. T h e method permitted quantitative measurements down to 0.10 pg/ml. T h e concentrations below this level were calculated as zero.
Cat 0-0
259
.
I5mg/kg i.v.
Phannacokinelic calculations
Plasma peak concentration (C& and time to reach this concentration (tmax) were read from the individual data. T h e area under the time-concentration curve (AUC (0-00))was calculated by the trapezoidal method u p to the last sample point (48 h) and extrapolated to infinity by using ICPHAKM computer program (Gomeni & Gomeni, 1978). Apparent total body clearance (CL) was calculated as DoselAUC (0-m) and apparent volume of distribution, V d , is given by clearance divided by the terminal slope. Apparent elimination half-life (t,J was calculated from the terminal slope o f the time-concentration curve.
0
2
4
6
8
10
12
24
48
Time (h) FIG. 1. Plasma tinidazole concentrations in dogs (upper panel) and cats (lower panel) after intravenous or oral administration of tinidazole 15 nigl kg or 30 mglkg. hlean f SEM are shown (n = 6 in each group except 30 mglkg p.0. in cats where n = 5).
Analysis of variance using subject and treatment as factors followed by Tukey HSD test was employed in the statistical analysis of the data. However, for differences between 1,,, values in oral dosing the Wilcoxon signedrank test was used. AUC (0-0))after 30 mg/kg p.0. was corrected for dose before the statistical analysis with SAS statistical software.
after oral administration were not different from those after intravenous administration. A dose of 30 mg/kg p.0. in dogs resulted in significantly higher peak concentration of tinidazole (37.9 pg/ml) than the lower dose 15 mg/kg p.0. (17.8 pg/ml). T h e t,/2 after 30 mg/kg p.0. in dogs was also significantly longer than after 15 mg/kg i.v. or 15 mg/kg P.o., while no significant differences were observed in other parameters. In cats no significant differences were observed in any parameters between the various doses.
RESULTS
DISCUSSION
T h e mean plasma concentrations 6f tinidazole in dogs and cats after i.v. and p.0. administration are shown in Fig. 1. T h e average pharmacokinetic parameters are summarized in Tables I and 11. Oral absorption of tinidazole was complete after both doses in dogs and cats. Both in dogs and cats AUC (0-m) values corrected for dose
Nitroimidazoles have a wide spectrum of activity against anaerobic bacteria Uokipii & Jokipii, 1977; Carmine et al., 1982; Prescott & Baggot, 1988). I n small animal practice metronidazole has been proven to be effective in the treatment of disease conditions such as gingivitis, periodontitis, abscesses and anal sac infections, chronic diarrhoea without diagno-
Slntislics
-.
260 E. Sarkiulu et al. T A B L E 1. Pharmacokinetic parameters of tinidazole in dogs after intravenous and oral administration (Mean f SEM) 15 mg/kg
30 'mglkg
p.0.
p.0.
142.71 f 12.29
17.78 f 0.45h 1.2 k 0.1 158.68 f 6.06
110.4 2 11.3 702.6 2 77.2 4.4 k 0.04
95.3 f 3.7 623.7 k 18.3 4.6 f 0.3
37.91 f 0.76h 1.6 f 0.2 378.15 f 50.53 189.07 f 25.27 90.3 f 15.8 678.2 +. 53.0 5.7 f 0.6"
15 mg/kg L.V.
C,,,, (w/ml)
23.98 f 1.34
(h)
,,t
AUC (0-m) (pg x h/ml) AUC,,,,,' (vg x hlmU CL t m l 4 x kg)l V , (mpkg) l,,,
(h)
"
P < 0.05 as compared with other trratments; P < 0.01 as cornpared with other treatments; AUC,,,,, = AL'C (0-m) corrected for
'
dose. T A B L E 11. Pharmacokinetic parameters of tinidazole in cats after intravenous and oral administration (Mean 5 SEM). N o statistically significantdifferences were observed in the parameters between the various doses 15 mg/kg
15 ing/kg p.0.
30 mg/kg
332.68 & 37.63
22.53 f 1.22 3.4 k 0.9 339.35 f 12.89
47.9 +- 4.7 548.4 2 52.8 8.4 2 1.0
44.6 f 1.6 538.5 f 35.8 8.4 f 0.6
33.61 f 1.57 2.8 5 0.8 571.91 f 42.63 238.30 f 5 I .48 53.7 f 3.8 705.8 f 37.2 9.2 f 0.6
I.V.
C,,,,, (Fg/111l) t,,,.,, (h) AVC (0-m) (pg X h/nil) AUC,,,,.' (pg X h/nil) CL (mVh kg) V,I W k g ) 1112 (h)
42.64 2 9.70
p.0.
~~~~
' AUC,,,,,
= AUC (0-m)
corrected for close
sed bacterial cause in dogs, and enteritis caused by Giardiu lmhlicl (Prescott & Baggot, 1988).Other infections where anaerobes have been cultured are osteomyelitis, peritonitis, pyothorax, pyometra and animal bite wounds (Hirsch el al., 1979; Goldstein el al., 1984; Johnson el al., 1984; Kanoe el al., 1984; Scott el al., 1984). Since the anti-bacterial spectrum of tinidazole is closely related to that of metronidazole (Carmine el al., 1982; Sande & Mandell, 1985) tinidazole could be used for the same indications. T h e present results show that tinidazole is completely absorbed after oral administration in dogs and cats. This is consistent with human studies reporting oral bioavailability of 90% or more (Carmine el al., 1982; Wood el
al., 1982). I n line with human data (Charuel el (11.. 1981) n o indication of non-linearity in the pharmacokinetics of tinidazole was observed between oral doses of 15 and 30 niglkg in dogs or cats in the present study. Total plasma clearance (CL) of tinidazole was twice as high in dogs resulting in a twofold longer elimination half-life ( l i p ) in cats. Accordingly, higher plasma tinidazole levels were maintained for a longer time in cats than in dogs. Interestingly, the t112 of tinidazole in dogs was about equal to that of metronidazole (Neff-Davis el al., 1981) although the tlI2 of tinidazole in man is clearly longer than that of metronidazole (Welling & Monro, 1972; Mattie el al., 1982). At the present time data a r e not available to allow comparison of tinidazole and metronidazole
Pha,?iiacokinefics of f i n i d m o l e 26 1
in cats. MZC values for tinidazole against most common anaerobic bacteria are generally below 2 vg/ml although some Bacteroides species can have MZC values of 6.3 pg/ml or even higher Uokipii & Jokipii, 1977; Rodriquez ef al., 1977; Heimdahl el al., 1980; Olsson-Liljeqvist & Nord, 1981). In the present study, these levels were exceeded in plasma in both dogs and cats after a single oral dose of 15 mg/kg. In dogs the average plasma tinidazole concentration was 3.7 pg/ml 12 h and in cats 4.3 pg/ml 24 h after a single dose of 15 mg/kg. Tinidazole penetrates well into various tissues and drug concentrations in most target tissues similar to that in plasma have been observed Uokipii ef al., 1977; Ripa el al., 1977; Heimdahl ef al., 1980; von Konow & Nord, 1982; Wood el al., 1982). O n the basis of these single dose results oral administration of 15 mg/kg once daily could be assumed to be a safe and effective dosage in cats. In dogs twice-daily oral administration at the same dose level (15 mg/kg) would seem to be appropriate in maintaining plasma levels exceeding the MIC values. T h e once-daily administration of 30 mg/kg in dogs could be used because it has been shown that the repeated administration of higher doses have not resulted in cohsiderable accumulation of the drug in tissues (Kimura ef al., 1974). In conclusion, tinidazole has been found to be well-absorbed after oral administration in dogs and cats and therapeutic tinidazole concentrations in plasma are achieved. Tinidazole seems to offer the possibility of the effective treatment of anaerobic infections in small animal practice.
ACKNOWLEDGMENTS This study has been financially supported by Orion Pharmaceutica. T h e skilful technical assistance of Kaarina Meller, Sirpa Soini, Laura Wessman and Johanna, Bjorkroth is greatly acknowledged.
REFERENCES Anderson, K.E. (1 981) Pharniacokinetics of nitroimidazoles. Spectrum of adverse reactions. Smiidinnvinii Jouninl of Infecfiotu Diserues, (Suppl. 26). 60-67.
Carmine, A.A., Brogden, R.N., Heel, R.C. Speight, T.M. & Avery, G.S. (1982) Tinidazole in anaerobic infections. A review of its antibacterial activity, pharmacological properties and therapeutic efficacy. Drugs, 24, 83-1 17. Charuel, C., Nachbaur, J., Monro, A.M. & de Palol, J. (1981) T h e pharmacokinetics of intravenous tinidazole i n man. Jourirnl of Aiifiwicrobial CIiemotlierapy, 8, 343-346. Cossu, F., Rombi, G.P., Mazza, S. & Facchini, A. (1 986) Radiosensitization by tinidazole: pharmacokinetic study. Iii/eriintioiinl Joiiriial of Clinicnl Phariiincolugy niid Research, 6, 3 17-323. Dow, S.W. (1988) hlanagenient of anaerobic infections. In The VeferinaT Clinics of Norfk Aviericn: Small Animal Practice, Clitiicnl Plcarinacology, Ed. Papich, M.G. 18, No. 6, 1167-1 182. W.B. Saunders Company, Philadelphia. Goldstein, E.J.C., Citron, D.M. & Finegold, S.M. ( 1984) Role of anaerobic bacteria in bite-wound infections. Reviews of Iitferfious Diseases, 6, 177183. Gonieni, C. & Gonieni. R. (1978) I C ~ I A H L I Interac: tive graphic package for pharmacokinetic analysis. Coiiipu/ers mid Biomedicnl Resrurcli, 11, 345361. Heinidahl, A., Nord, C.E. & Okuda, K. (1980) Effect of tinidazole on the oral, throat and colon microflora of man. Medical hficrobiulom rtiirl I l i i i t i t i d i > ~ ,168,
1-10.
Hirsch, D.C., Biberstein, E.L. 8c Jang, S.S. (197!)) 0hlig;ite anaerobes i n clinical veterin;iry practice. Jotiriiril of Cliiiiccil , \ l i c I o b i o l o ~ . 10, 188-1 I) I. Isogii, E., Isogai. H.. hliura, H., T;ik;ino, K., Aoi, Y.. Hay;ishi, M. B Naniioka, S. (19x9) Oral florx of niongrel and beagle dogs with pcriodontal disease. Jripoiie.~Joiiriiril (fVc*frriirniyScirircr, 51, 1 1 0 - 1 IS. Johiison, K.A., Lonias, G . R . 8c Wood. A.K.W. (1984) Osteoniyelitis in dogs and cats caused by anaerobic bacteria. Aiis/rulifiii V&riiiciiy Joui-iid, 61, 57-61. Jokipii, A.M.M. B Jokipii. L. (1977) Bacterial activity of tinidazole. Chriiiotlroi-apy. 23, 25-3 1. Jokipii, A.hI.M., hlyllyl~i, V.V., Hokkanen, E. 8c
Jokipii. L. (1977) Penetration of the blood brain barrier by nietronidazole and tinidazole. Jotiriial of Aiitiinicrobinl Cliemo/lirrop?, 3, 239-249. Kmoe, hl., Kido. hl. & Toda, M. (1984) Obligate anaerobic bacteria found in canine and feline purulent lesions. Britisli Veteiinmy Jouriinl, 140, 25 7-262. Kiniura, Y., Ohki. K., Kano, H. & Noguchi. Y. ( 1974) Absorption, distribution, excretion and metabolism of tinidazole. Plinriiincoiiirfri~s,8, 573587. hlallonee, D.H., Harvey, C.E., Veriner, M. & Hammond, B.F. ( 19Y8) Bacteridlogy of periodontal disease in the cat. A r c h e s oforal Biology. 33, 677683. Mattie, H., Dijknians, B.A.C. & van Gulpen, C. (1982) T h e pharniacokinetics of nietronidazole and tinidazole in patients with mixed aerobicanaerobic infections. Jouriial of Aiitiisicrobinl Clreinotliernp?. 10 (Suppl. A), 59-64.
262
E . Sarkzula et al.
Neff-Davis, C.A., Davis, L.E. & Gillette, E.L. (1981) Metronidazole: a method for its determination in biological fluids and its disposition kinetics in the dog. Journal of Veteriiurry Plmrniacology and Tlrerapeutics. 4, 121-127. Olsson-Liljeqvist. B. & Nord, C.E. (1981) f i i uilro susceptibility of anaerobic bacteriia to nitroimidazoles. Scawdinauiair Journal of fttfectious Durases, (Suppl. 26), 42-45. Prescott, J.F. & Baggot, J.D. (1988) Nucleic acid inhibitors. Nitroirnidazoles. In Aiitiiiricubial Tlierapy in Veterinary Medicine, 1st edn. Eds Prescott. J.F. & Baggot, J.D. pp. 213-217. Blackwell Scientific Publications, Boston. PyoPAla, S., Kotilainen, T., Silvennoinen, P., HSnninen. U.. Mero. M. & Kaartinen, L. (1990) Pharniacokinetics of tinidazole in the horse. Jvunial of Veterinary Plmriiiacology and Tlierapeutics, 13, 7680. Ripa, T., Westroni, L., Mardh, P-A. It Andersson, K-E. (1977) Concentrations of tinidazole in body fluids and tissues in gynaecological patients. Cliet~iotlwrapy.23, 227-235. Rodriguez, J.A.G., Sanchez. J.E.G., Gonzales, M.C.S.& Prieto, J.P. (1977) T h e sensitivity of anaerobic Gram-negative bacilli to four nilroimidazole derivatives. Plianiratlwrapeutica, 1 , 573582. Sande. M.A. & Mandell. G.L. (1985) Antimicrobial
agents. In Tlw Pliarinacological Basis of Tlierupeutirs 7th edn. Eds Goodnian Gilman, A., Goodman, L.S., Rdkl, T.W. & Murdd, F., pp. 1066-1239. Macmillan, New York. Sawyer, P.R., Brogden, R.N., Pinder, K.M., Speight, T.M. & Avery, G.S. ( 1 976) Tinidazole: a review of its antiprotozoal activity and therapeutic efficacy. Drugs, 11, 423-440. Scott, P.C., Taylor, T.K., Gilniore, J.F. & Hart, A.T. (1984) Suppurative peritonitis in cats associated with anaerobic bacteria. Aurlraliati V ef ri l ’ i t qJuurtial, 61, 367-368. Webster, L.T. (1985) Drugs used in the clieniotherapy of protozoal infections. In The Plrarinucological Basis of Tlierapeutics 7th edn. Eds Goodinan Gilman, A., Goodman. L.S.. Rall, T.W. & Murad. F., pp. 1049-1057, Macniillan, New York. Welling, P.G. (G Monro, A.M. (1972) T h e pharmacokinetics of nietronidazole and , tinitlazole in man. ArriieiiiiifIel-Forscliuii~, 22, 2 128-2 132. von Konow, L. & Nord. C.E. (1982) Concentrations of tinidazole and metronidazole in serum, saliva Clieiitoand alveolar bone. Jouriml o/ Airt~iiiicrol~ial therapy. 10 (Suppl. A), 165-172. Wood, B.A., Faulkner, J.K. & Moiiro, A.M. (1982) T h e pharniacokinetics, nietabolisni and tissue distribution 0 1 tiniclazole. Jouriral of A iifiiiiicrobial Clie,rollreral?y, 10 (Suppl. A), 43-57.
J. net. Pharmncol. Therap. 14,257-262, 1991.
Pharmacokinetics of tinidazole in dogs and cats E. SARKIALA, A. JARVINEN*, S. V A L T T I L A t & M. M E R O Department of Clinical Sciences, College of Veterinary Medicine, Helsinki,* Department of Pharmacology and Toxicology, University of Helsinki, and t Orion Pharmaceutica, Analytical Department, Espoo, Finland
Sarkiala, E., Jgrvinen, A.. Valttila, S., Mero, M. Pharmacokinetics of tinidazole in dogs and cats. J. vet. P f u r m u v l . TIierup. 14, 257-262. Pharmacokinetics of tinidazole in dogs and cats after single intravenous (15 mg/ kg) and oral doses (15 mg/kg o r 30 mg/kg) were studied in a randomized crossover study. Tinidazole was completely absorbed at both oral dose levels in cats and dogs. Peak tinidazole concentration in plasma was 17.8 pg/ml in dogs and 22.5 pg/ml in cats after 15 mg/kg p.o. T h e oral dose of 30 rng/kg resulted in peak levels of 37.9 pg/ml in dogs and 33.6 pg/ml in cats. T h e apparent total plasma clearance of the d r u g was about twofold higher in dogs than in cats, resulting in an elimination half-life that was twice as long in cats (8.4 h) as in dogs (4.4 h). T h e apparent volume of distribution was 663 mVkg in dogs and 536 ml/ kg in cats. Therapeutic plasma drug concentrations higher than t h e M f C values of most tinidazole-sensitive bacteria were achieved for 24 h in cats and for 12 h in clogs after a single oral dose of 15 mg/kg. From the pharniacokinetic standpoint tinidazole seems to be well-suited to clinical use in small animal practice. Evu Sarkiuln, Drpnrtment vf Clinicul Scicmces, Cullegr vf Velrrinuty Midicine, Haviretilie, 57 00580 HeLsinki, Fiiclcnd.
INTRODUC’TION In the treatment of anaerobic o r mixed infections, a bacteriological diagnosis is seldom available at the time treatment is begun. Therefore, anti-microbial agents like chloramphenicol and clindamycin, which are effective against most anaerobes, are often preferred. However, since these agents can produce serious adverse effects their general use in infections that are not life-threatening can be questioned (Sande & Mandell, 1985;- Dow, 1988). Knowledge of the importance of anaerobic bacteria in infections like gingivitis and periodontitis also calls for the use of safer drugs in veterinary medicine (Mallonee et ul., 1988; Isogai et al., 1989). Several nitroimidazoles, like metronidazole and tinidazole, are widely used in humans, whereas only metronidazole has been used extensively in veterinary medicine. Nitroimi-
dazoles are bactericidal to most. Graninegative and also to many Gram-positive bacteria, including klactamase-producing Bric/rruidrs fragilis (Jokipii 8c Jokipii, 1977; Prescott & Baggot, 1988); they also have antiprotozoal activity (Webster, 1985). Moreover, they are known to have a wide therapeutic range and low toxicity. Tinidazole has been given in doses u p to 65 mg/kg to humans and 300 nig/kg to rats and monkeys without toxic or adverse reactions (Cossu el ul., 1986; Sawyer et al., 1976). Although nitroimidamles are generally well-tolerated they can cause gastrointestinal and cutaneous side-effects, thrombophlebitis after intravenous administration, headache, sleeplessness, depression, glossitis, stomatitis and dryness of the mucous membranes (Sawyer el ul., 1976: Andersson, 1981; Carmine et al., 1982; Webster, 1985). However, more serious adverse effects like neutropenia o r neurologic symptoms only 257
258 E . Sarkiula et al.
rarely occur, but prolonged high-dose therapy may be associated with carcinogenicity (Carmine et al., 1982; Webster, 1985). Tinidazole and metronidazole have been shown to be widely distributed in the body and to penetrate well into various tissues in man as well as in the dog and rat (Kimura el al., 1974; Anderson, 1981; Wood el ul., 1982). T h e total clearance of tinidazole in man is only about one-half of that of metronidazole resulting in a twofold longer elimination half-life and higher and more stable plasma concentrations compared with metronidazole (Welling & Monro, 1972; Mattie el al., 1982). Similarly, in horses the half-life of tinidazole was found to be 5.2 h and that of metronidazole 3.9 h (Prescott & Baggot, 1988; Pyorala et ul., 1990). T h e longer elimination half-life and the wide therapeutic range of tinidazole could be of advantage in veterinary medicine by allowing longer dosing intervals. Despite its obvious advantages over metronidazole, the pharmacokinetics of tinidazole has not been studied in cats and only one report exists on its pharmacokinetics in dogs (Kimura et al., 1974). T h e present study was undertaken to characterize the pharmacokinetics of tinidazole in dogs and cats after single intravenous (i.v.) and oral (p.0.) doses. To provide a basis for a rational dosage regimen in future studies and to test the linearity of the pharrnacokinetics of tinidazole two oral doses were used.
animal weight, was given. For the dogs the drug was hidden in a small piece of commercial dog food, while the cats received the drug together with 5 ml of water. For intravenous (i.v.) administration, tinidazole 5 mg/ml sohtion (Orion Pharmaceutica, Finland,. batch OCO42-1) was given as a bolus injection over 2 min.
Study design T h e study utilized a cross-over design. Each animal was given 15 mg/kg tinidazole both i.v. and p.0. and 30 mg/kg p.0. in a random order. A wash-out period of at least 2 weeks was allowed between the phases of the study. An indwelling plastic catheter was inserted in the cephalic vein of the dogs and in the jugular vein of the cats for collection of blood samples (4 ml each). T h e cats were sedated by giving an intramuscular (im.) injection of 80 yg/kg medetomidine (Farmos Group Ltd, Finland). After the catheter was inserted, the sedation was antagonized with atipamezole (32 pg/kg im.) (Farmos Group Ltd, Finland). Blood samples were taken immediately before and at 2, 4, 8, 16, 30 min and 1, 2, 4, 6, 12, 24, 48 h after i.v. administration and 0, 0.25, 0.5, 1, 1.5, 2, 3, 6, 8, 12, 24, 48 h after oral administration. All blood samples were taken in heparinized tubes. Plasma was separated by centrifugation and immediately deep frozen at -70 "C until assayed.
MATERIALS AND M E T H O D S Analytical methods AnimaLr and drugs
Six healthy Beagle dogs, four males and t w o females, were used. T h e dogs ranged in age from 4 to 5 years and in weight from 10.5 to 15.0 kg (mean 12.1 kg). In addition, six domestic shorthair cats (three males and three females) w e r e used. Their age ranged between 1 and 2 years and their weight from 2.4 to 3.7 kg (mean 2.8 kg). All animals were fasted over-night but water was freely accessible before the study. Tinidazole tablets (150 mg or 500 mg; Orion Pharmaceutica, Finland, batch OD 1-3 and NC 1-6, respectively) were divided and a piece of tablet, adjusted according to the
Concentrations of tinidazole in plasma samples were determined by high-performance liquid chromatography (HPLC) with UV detection at 313 nm. T h e method involved extraction of the plasma samples (0.2 ml) with 3 ml of dichloromethane. T h e organic phase was evaporated to dryness and dissolved into 200 y1 of the mobile phase and an aliquot of 20 ~1 was analysed by HPLC. T h e method was validated with regard to linearity, accuracy, precision, recovery and specificity. T h e method gave interferencefree and linear results over the concentration range 0.10-45.45 pg/ml. T h e recovery was more than 99% at all concentration levels
Plurmucokinetics of liniduzole
studied. T h e relative standard deviation of quality control samples 22.73 and 5.68 Fg/ml of tinidazole were 5.0 and 6.0% (n = 19), respectively. T h e precision of six successively analysed spiked plasma samples at the concentrations of 45.45, 13.64, 1.36 and 0.10 pg/ml of tinidazole were 1.8, 1.3, 1.7, and 1.2%, respectively. T h e method permitted quantitative measurements down to 0.10 pg/ml. T h e concentrations below this level were calculated as zero.
Cat 0-0
259
.
I5mg/kg i.v.
Phannacokinelic calculations
Plasma peak concentration (C& and time to reach this concentration (tmax) were read from the individual data. T h e area under the time-concentration curve (AUC (0-00))was calculated by the trapezoidal method u p to the last sample point (48 h) and extrapolated to infinity by using ICPHAKM computer program (Gomeni & Gomeni, 1978). Apparent total body clearance (CL) was calculated as DoselAUC (0-m) and apparent volume of distribution, V d , is given by clearance divided by the terminal slope. Apparent elimination half-life (t,J was calculated from the terminal slope o f the time-concentration curve.
0
2
4
6
8
10
12
24
48
Time (h) FIG. 1. Plasma tinidazole concentrations in dogs (upper panel) and cats (lower panel) after intravenous or oral administration of tinidazole 15 nigl kg or 30 mglkg. hlean f SEM are shown (n = 6 in each group except 30 mglkg p.0. in cats where n = 5).
Analysis of variance using subject and treatment as factors followed by Tukey HSD test was employed in the statistical analysis of the data. However, for differences between 1,,, values in oral dosing the Wilcoxon signedrank test was used. AUC (0-0))after 30 mg/kg p.0. was corrected for dose before the statistical analysis with SAS statistical software.
after oral administration were not different from those after intravenous administration. A dose of 30 mg/kg p.0. in dogs resulted in significantly higher peak concentration of tinidazole (37.9 pg/ml) than the lower dose 15 mg/kg p.0. (17.8 pg/ml). T h e t,/2 after 30 mg/kg p.0. in dogs was also significantly longer than after 15 mg/kg i.v. or 15 mg/kg P.o., while no significant differences were observed in other parameters. In cats no significant differences were observed in any parameters between the various doses.
RESULTS
DISCUSSION
T h e mean plasma concentrations 6f tinidazole in dogs and cats after i.v. and p.0. administration are shown in Fig. 1. T h e average pharmacokinetic parameters are summarized in Tables I and 11. Oral absorption of tinidazole was complete after both doses in dogs and cats. Both in dogs and cats AUC (0-m) values corrected for dose
Nitroimidazoles have a wide spectrum of activity against anaerobic bacteria Uokipii & Jokipii, 1977; Carmine et al., 1982; Prescott & Baggot, 1988). I n small animal practice metronidazole has been proven to be effective in the treatment of disease conditions such as gingivitis, periodontitis, abscesses and anal sac infections, chronic diarrhoea without diagno-
Slntislics
-.
260 E. Sarkiulu et al. T A B L E 1. Pharmacokinetic parameters of tinidazole in dogs after intravenous and oral administration (Mean f SEM) 15 mg/kg
30 'mglkg
p.0.
p.0.
142.71 f 12.29
17.78 f 0.45h 1.2 k 0.1 158.68 f 6.06
110.4 2 11.3 702.6 2 77.2 4.4 k 0.04
95.3 f 3.7 623.7 k 18.3 4.6 f 0.3
37.91 f 0.76h 1.6 f 0.2 378.15 f 50.53 189.07 f 25.27 90.3 f 15.8 678.2 +. 53.0 5.7 f 0.6"
15 mg/kg L.V.
C,,,, (w/ml)
23.98 f 1.34
(h)
,,t
AUC (0-m) (pg x h/ml) AUC,,,,,' (vg x hlmU CL t m l 4 x kg)l V , (mpkg) l,,,
(h)
"
P < 0.05 as compared with other trratments; P < 0.01 as cornpared with other treatments; AUC,,,,, = AL'C (0-m) corrected for
'
dose. T A B L E 11. Pharmacokinetic parameters of tinidazole in cats after intravenous and oral administration (Mean 5 SEM). N o statistically significantdifferences were observed in the parameters between the various doses 15 mg/kg
15 ing/kg p.0.
30 mg/kg
332.68 & 37.63
22.53 f 1.22 3.4 k 0.9 339.35 f 12.89
47.9 +- 4.7 548.4 2 52.8 8.4 2 1.0
44.6 f 1.6 538.5 f 35.8 8.4 f 0.6
33.61 f 1.57 2.8 5 0.8 571.91 f 42.63 238.30 f 5 I .48 53.7 f 3.8 705.8 f 37.2 9.2 f 0.6
I.V.
C,,,,, (Fg/111l) t,,,.,, (h) AVC (0-m) (pg X h/nil) AUC,,,,.' (pg X h/nil) CL (mVh kg) V,I W k g ) 1112 (h)
42.64 2 9.70
p.0.
~~~~
' AUC,,,,,
= AUC (0-m)
corrected for close
sed bacterial cause in dogs, and enteritis caused by Giardiu lmhlicl (Prescott & Baggot, 1988).Other infections where anaerobes have been cultured are osteomyelitis, peritonitis, pyothorax, pyometra and animal bite wounds (Hirsch el al., 1979; Goldstein el al., 1984; Johnson el al., 1984; Kanoe el al., 1984; Scott el al., 1984). Since the anti-bacterial spectrum of tinidazole is closely related to that of metronidazole (Carmine el al., 1982; Sande & Mandell, 1985) tinidazole could be used for the same indications. T h e present results show that tinidazole is completely absorbed after oral administration in dogs and cats. This is consistent with human studies reporting oral bioavailability of 90% or more (Carmine el al., 1982; Wood el
al., 1982). I n line with human data (Charuel el (11.. 1981) n o indication of non-linearity in the pharmacokinetics of tinidazole was observed between oral doses of 15 and 30 niglkg in dogs or cats in the present study. Total plasma clearance (CL) of tinidazole was twice as high in dogs resulting in a twofold longer elimination half-life ( l i p ) in cats. Accordingly, higher plasma tinidazole levels were maintained for a longer time in cats than in dogs. Interestingly, the t112 of tinidazole in dogs was about equal to that of metronidazole (Neff-Davis el al., 1981) although the tlI2 of tinidazole in man is clearly longer than that of metronidazole (Welling & Monro, 1972; Mattie el al., 1982). At the present time data a r e not available to allow comparison of tinidazole and metronidazole
Pha,?iiacokinefics of f i n i d m o l e 26 1
in cats. MZC values for tinidazole against most common anaerobic bacteria are generally below 2 vg/ml although some Bacteroides species can have MZC values of 6.3 pg/ml or even higher Uokipii & Jokipii, 1977; Rodriquez ef al., 1977; Heimdahl el al., 1980; Olsson-Liljeqvist & Nord, 1981). In the present study, these levels were exceeded in plasma in both dogs and cats after a single oral dose of 15 mg/kg. In dogs the average plasma tinidazole concentration was 3.7 pg/ml 12 h and in cats 4.3 pg/ml 24 h after a single dose of 15 mg/kg. Tinidazole penetrates well into various tissues and drug concentrations in most target tissues similar to that in plasma have been observed Uokipii ef al., 1977; Ripa el al., 1977; Heimdahl ef al., 1980; von Konow & Nord, 1982; Wood el al., 1982). O n the basis of these single dose results oral administration of 15 mg/kg once daily could be assumed to be a safe and effective dosage in cats. In dogs twice-daily oral administration at the same dose level (15 mg/kg) would seem to be appropriate in maintaining plasma levels exceeding the MIC values. T h e once-daily administration of 30 mg/kg in dogs could be used because it has been shown that the repeated administration of higher doses have not resulted in cohsiderable accumulation of the drug in tissues (Kimura ef al., 1974). In conclusion, tinidazole has been found to be well-absorbed after oral administration in dogs and cats and therapeutic tinidazole concentrations in plasma are achieved. Tinidazole seems to offer the possibility of the effective treatment of anaerobic infections in small animal practice.
ACKNOWLEDGMENTS This study has been financially supported by Orion Pharmaceutica. T h e skilful technical assistance of Kaarina Meller, Sirpa Soini, Laura Wessman and Johanna, Bjorkroth is greatly acknowledged.
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