Pharmacokinetics of gentamicin in channel catfish (Ictalurus punctatus)

The pharmacokinetics of gentamicin were determined in male and female Ictalurus punctatus weighing between 0.3 kg and 1.7 kg. Plasma gentamicin concentrations were measured by radioimmunoassay technique. In the 1st experiment, an intracardiac bolus dosage of gentamicin (1 mg/kg) was given to 10 channel catfish. Samples of blood were obtained (by cardiac puncture) immediately before gentamicin was given and at various times over a 24-hour period. The gentamicin half-life was 770 minutes (beta = 0.0009 +/- 0.0003 minute-1). The maintenance therapeutic IV dosage of gentamicin was calculated to be 1.6 mg/kg given at 33.2-hour intervals. In the 2nd experiment, an IM dosage of the drug (1 mg/kg) was given to 9 channel catfish, and samples of blood were obtained at various times over a 24-hour period. The gentamicin half-life was 770 minutes (beta = 0.0009 +/- 0.0002 minutes-1). The maintenance therapeutic IM dosage of gentamicin was calculated to be 3.5 mg/kg given at 33.2-hour intervals. The IM bioavailability of gentamicin in channel catfish was estimated to be 60%. Other pharmacokinetic values were also determined. It was concluded that the therapeutic regimen of choice for gentamicin in channel catfish was 3.5 mg/kg given IM with 33-hour intervals between doses.