PHARMACOKINETICS AND INTRAMUSCULAR BIOAVAILABILITY OF AMIKACIN IN CHICKENS FOLLOWING SINGLE AND MULTIPLE DOSING

The pharmacokinetics of amikacin were studied in healthy mature female chickens (n = 6). Single doses of amikacin were injected as an i.v. bolus (10 mg/kg) and i.m. (20 mg/kg) into the same birds with a 30-day rest period between treatments. Amikacin was determined by the fluorescence polarization immunoassay method. The i.v. pharmokinetics could be described by a two-compartment model with a t1/2-alpha of 0.150 +/- 0.064 h and a t1/2-beta of 1.44 +/- 0.34 h. The total body clearance was 0.109 +/- 0.017 1/h/kg and the volume of distribution at steady-state was 0.193 +/- 0.060 1/kg. Following a single i.m. injection, the peak plasma concentration (C(max)) was 50.79 +/- 4.05 -mu-g/ml and occured at 0.50 +/- 0.26 h. The i.ni. extent of absorption was 91.2 +/- 17.6%. Simultaneous modeling of i.v. and i.ni. results provided estimates of an absorption half-life of 0.480 +/- 0.158 h. The i.m. pharmacokinetics after repeated administration were studied following the tenth close (20 mg/kg, every 8 h). The C(ss)max was 38.58 +/- 6.96-mu-g/ml and occurred at 0.79 +/- 0.37 li, and the biological half-life of amikacin was 1.86 +/- 0.47 h. The multiple dosing yielded peak concentrations of 39-mu-g/ml and trough concentrations of 3.26-mu-g/ml. Based on these data, the recommended amikacin dosage in chickens is 20 mg/kg body weight every 8 h.