Pharmacokinetics of tobramycin in the camel

The pharmacokinetics of tobramycin were determined in six healthy camels (Camelus dromedarius) following the intravenous (i.v.) and intramuscular (i.m.) administration of single doses of tobramycin sulphate (40 mg/ml). The half-life to tobramycin was 189 +/- 21 min and the mean residence time was 254 +/- 26 min. The apparent volume of distribution (area method) was 245 +/- 21 ml/kg, while volume of the central compartment of the two-compartment pharmacokinetic model was 110 +/- 12 ml/kg. The clearance (systemic) of tobramycin was 0.90 +/- 0.10 ml/min/kg. Values of the pharmacokinetic parameters suggest that glomerular filtration rate is lower in camels than in other ruminant species, horses, dogs and cats. Following i.m. administration of the dose (1.0 mg/kg), the drug was rapidly absorbed with peak serum concentration of 3.32 +/- 0.59 micrograms/ml at 20-30 min; the absorption half-life was 3.9 +/- 0.9 min. The systemic availability of tobramycin was 90.7 +/- 14.4%. The apparent half-life was 201 +/- 40 min, which was not significantly longer than the half-life following i.v. administration of the drug. Based on the pharmacokinetic values obtained in this study, a dosing rate of 2.5 mg/kg administered by i.m. injection at 12-h intervals can be recommended. This dosage regimen should achieve an average steady state serum concentration of 4 micrograms/ml with peak serum concentration approaching, but not exceeding, 10 micrograms/ml.