Amikacin pharmacokinetics and the effects of ambient temperature on the dosage regimen in ball pythons (Python...

The serum concentration of amikacin following intracardiac and i.m. administration of amikacin (3.48 mg/kg) in 12 ball pythons (Python regius) housed at 25 degrees C and 37 degrees C was studied. Blood samples were collected by cardiocentesis at intervals up to 144 hr after administration of amikacin. Drug concentration-versus-time curves following intracardiac administration at both temperatures best fit a two-compartment open model. For snakes housed at 37 degrees C, the extrapolated time 0 concentration (mean +/- SD) was 17.64 +/- 3.5 micrograms/ml with a median elimination half-life of 4.5 days. The maximum concentrations were 11.98 +/- 1.67 micrograms/ml and 13.87 +/- 2.61 micrograms/ml for snakes housed at 25 degrees C and 37 degrees C respectively. There were no significant pharmacokinetic differences among the snakes housed at 25 degrees C and 37 degrees C. Model-independent parameters were area under the curve, 69,900 +/- 0.011 micrograms.min/ml, apparent volume of distribution at steady state, 410 +/- 106 ml/kg, clearance, 0.036 +/- 0.009 ml/min/kg, and mean residence time, 3,530 +/- 273.7 minutes. Mean serum amikacin concentrations did not reach the recommended therapeutic peak concentrations for mammals (25 micrograms/ml). In addition, the amikacin serum concentration did not fall below the recommended therapeutic trough concentrations (2 micrograms/ml) by 6 days. The serum amikacin concentrations were efficacious based on the area under the curve. Therefore, amikacin (3.48 mg/kg) administered i.m. to ball pythons should produce maximum serum concentrations against most pathogenic bacteria. In this study, it would have taken another half-life, or 4.5 days, before trough concentrations of 2 micrograms/ml were achieved. To prevent accumulation, a one-time administration of amikacin may be appropriate.