Biological Half-Life of Gentamicin in Gopher Snakes

Abstract

SUMMARY AND CONCLUSIONS A study was performed to determine the biological half-life and plasma concentrations of gentamicin in gopher snakes. The snake plasma was assayed for gentamicin, using a microbiological agar well diffusion technique. In the 1st study, 10 gopher snakes (groups A and B) were each given a single injection of gentamicin. They were anesthetized and samples of blood were collected each day to determine the antibiotic half-life. The average half-life was 82 hours ( sd = 31) at an environmental temperature of 24 C. The variations in the results were probably due to metabolic differences within individual snakes. In another study, 11 gopher snakes were treated with serial injections of gentamicin for about 2 weeks. Group C snakes were given gentamicin at a dose level of 2.5 mg/kg of body weight/72 hours, and those in group D were given a dose level of 2.5 mg/kg of body weight/day. Group E snakes were given gentamicin at a dose level of 5.0 mg/kg of body weight/72 hours, and group F snakes were given gentamicin at a dose level of 5.0 mg/kg of body weight/day. The snakes given gentamicin each day reached very high antibiotic concentrations in their plasma. With the long half-life of gentamicin in snakes, the gentamicin accumulation resulted from daily administration. Plasma gentamicin concentrations in the snakes that were treated every 72 hours were lower than the concentrations in the daily treated snakes. However, these values were still higher than the therapeutic concentration recommended for human beings. It was concluded that gentamicin should not be administered to snakes daily, but rather every 72 hours, and that a prolonged therapeutic dosing should be avoided.