Amoxicillin pharmacokinetics in harbor seals (Phoca vitulina) and northernelephant seals (Mirounga angustirostris) following single dose intravenousadministration: implications for interspecific dose sealing

The pharmacokinetics of sodium amoxicillin after a single intravenous dose of 20 mg/kg were determined in ten harbor seals (Phoca vitulina) and ten no rthern elephant seals (Mirounga angustirostris). The seals ranged in age fr om 1 to 6 months and the mean weights were 11.7 kg (range, 9.5-18.5 kg) for harbor seals and 47.1 kg (range, 39.5-61.4 kg) for elephant seals. The med ian half-life of amoxicillin (quartiles) in harbor seals, 1.5 (1.0-3.1) h, was not statistically different from that of elephant seals, 2.0 (1.4-3.8) h, nor were the differences between the terminal elimination rate constants between the two species. The only statistically significant differences be tween species were for area-under-the-curve (AUC), and total systemic clear ance. The lack of statistical significance for differences in the volume of distribution at steady-state (Vss) may have been due to minor differences in the time frame of data collection and dose administered between the two groups. A true physiologic difference in drug handling, possibly related to renal perfusion or tubal secretory efficiency could affect amoxicillin kin etics in these species, and longer administration intervals may be appropri ate for elephant seals as compared to harbor seals when administering multi ple dose amoxicillin therapy at 20 mg/kg.