Pharmacokinetics of Metronidazole in the Yellow Rat Snake, Elaphe obsoleta quadrivitatta
J Herpe Med Surg 11[2]:4-8 Summer'01 Original Article 22 Refs

Anaerobic bacterial infections are a common problem in reptiles. This study examined pharmacokinetics of metronidazole, a drug used to treat anerobic infections, in wild-caught, yellow rat snakes, Elaphe obsoleta quadrivitatta. A preliminary trial evaluated 20 mg/kg and 100 mg/kg doses, each dose given orally to two rat snakes. Snakes were bled by cardiocentesis at 0, 4, 8, 11.5, and 23 hr. Plasma metronidazole levels were analyzed by high performance liquid chromatography and indicated that the 20 mg/kg dose produced peak metronidazole levels above the 2 - 4 ug/ml reported minimum inhibitory concentrations for most anaerobic bacterial pathogens in mammals. Steady state pharmacokinetics were then evaluated in five snakes. The snakes were given six doses of metronidazole, 20 mg/kg PO q 48 hr. Snakes were bled by cardiocentesis prior to treatment and at 0, 4, 8, 12, 24, and 48 hr after the initial and sixth treatment and at 74 hr following the sixth treatment. The predicted times of maximum metronidazole plasma levels were 1.4 hr following the initial treatment and 4.0 hr following the final treatment. Mean concentrations at these times were 14.2 ± 1.2 ug/ml and 12.8 ± 2.7 ug/ml, respectively. Mean plasma metronidazole concentrations remained above 4.0 ug/ml for 24 hr following the initial treatment and 4.0 hr following the final treatment. No adverse effects were observed in any snake. These data indicate that a metronidazole dosage of 20 mg/kg PO q 48 hr should be adequate for the treatment of most anaerobic infections in yellow rat snakes. [Abstract]