Abstract

Most antibiotic doses used in marine mammals are based on extrapolations from domestic species and empirical use. Few pharmacokinetic studies have been performed in marine mammals and those that have been on limited numbers of animals and rarely published. In this study, the pharmacokinetics of sodium amoxicillin was determined after a single intravenous administration in 8 northern elephant seal pups (Mirounga angustirostris) and 10 harbor seal pups (Phoca vitulina). The seals ranged in age from one to six months and the mean weights were 11.7 kg (range, 9.5-18.5 kg) for harbor seal pups and 47.1 kg (range, 39.5-61.4 kg) for elephant seal pups. Amoxicillin was administered at a dose of 20 mg/kg into the intravertebral extradural vein. Serial blood samples were drawn over a 24 hr. period from the same vein.

The mean ± SD half-lives for amoxicillin were 1.54 ± 1.09 hours in harbor seals and 2.38 ± 1.23 hours in elephant seals. The mean clearance and volume of distribution were 0.317 ± 0.134 L/kg/hr and 0.599 ± 0.280 L/kg respectively in harbor seals, and 0.131 ± 0.062 L/kg/hr and 0.416 ± 0.456 L/kg respectively in elephant seals. There were no significant differences between the volume of distributions and terminal elimination rate constants (half-lives) between the elephant seal and harbor seal pups. There was significant differences between the parameters of area-under-the-curve, mean residence time, and total systemic clearance.