Pharmacokinetics and urinary excretion of gentamicin in Bubalus bubalis calves following intramuscular administration

The pharmacokinetics and urinary excretion of gentamicin was studied in buffalo calves after a single intramuscular administration (10 mg kg-1). Kinetic determinants were calculated by using a two compartment open model. The absorption (t1/2Ka) and biological half lives (t1/2 beta) were calculated to be 0.43 +/- 0.08 and 3.79 +/- 0.23 h, respectively. The value of the apparent volume of distribution (VdB) was found to be 0.38 +/- 0.07 litre kg-1. The satisfactory intramuscular dosage regimen of gentamicin for buffalo calves would be 3.23 mg kg-1 as priming dose and 2.88 mg kg-1 as maintenance dose to be repeated at 12 hour intervals to achieve and maintain the therapeutic plasma levels within safe limits. Urinary excretion of gentamicin was very rapid during the first 12 hours as 48.07 +/- 1.39 per cent of the total administered dose was excreted unchanged during this period.