THERAPEUTICS

Drugs and dose rates used in pinnipeds are most fre­quently extrapolated from those used in domestic animals

Fig.

(see Appendix 4). The pharmacokinetics of two antimi­crobial agents with prolonged duration of action have been studied in pinnipeds. An extended-release form of ceftiofur (Excede_® Sterile Suspension, Zoetis, Rhodes, NSW), administered at 6.6 mg/kg IM to California sea­lions, maintained a plasma level >0.5 μg∕mL for 8 d (Meegan et al. 2013). Garcia-Parraga et al. (2016) evalu­ated the duration of cefovecin (Convenia®, Zoetis, Rhodes, NSW) plasma concentrations after single IM or SC injec­tion, at different doses 1-8 mg/kg, in 10 Patagonian sea­lions (Otaria flavescens) and found that cefovecin had a more prolonged pharmacokinetic profile than in any other species previously studied. Following SC adminis­tration, the plasma elimination half-life was 11.3-21.6 d. These findings were also observed in other sea-lion spe­cies (Garcia-Parraga et al. 2012). When using long-acting antibiotics, there is potential for development of bacterial resistance when antimicrobial concentrations are close to the minimum inhibitory concentration for normal flora and when drug activity is very prolonged. The authors cautioned that cefovecin should be reserved for particular cases based on clinical observations and specific microbi­ological diagnoses, and that total doses <8 mg/kg SC/IM should be considered in most cases, in order to shorten the duration of action. Although there have been no studies describing pharmacokinetic parameters in Australian pinniped species, both ceftiofur and cefovecin have been used at these ‘pinniped’ dose rates in long-nosed fur seals, Australian fur seals and Australian sea-lions (K Bodley pers. observ.; C Colitzpers. comm.; D Blyde pers. comm.).

6.