Pharmacokinetics of Moxidectin in Bare-Nosed Wombats (Vombatus ursinus) After Intravenous, Sub-Cutaneous and Transdermal Administration

The anti-parasitic drug moxidectin is a frontline treatment for sarcoptic mange in bare-nosed wombats (Vombatus ursinus), a disease causing significant animal welfare issues and instances of local population declines. Despite widespread usage, knowledge of species-specific pharmacokinetics of moxidectin in bare-nosed wombats is still limited. This study describes the clinical pharmacokinetics of moxidectin by intravenous, subcutaneous, and transdermal routes of administration in bare-nosed wombats. Plasma moxidectin concentration was assessed by liquid chromatography mass spectrometry and analysed by Bayesian hierarchical modelling. Plasma clearance was 1.11-1.85 mL/min/kg. The subcutaneous route showed biphasic absorption, dominated by a slow terminal absorption phase (80% of the effective dose of moxidectin was absorbed in this phase) with a half-life of approximately 631 h (26.3 days). The transdermal route had an estimated half-life of 21.78 h (1308) min. The average bioavailability was 0.59% and 95.7% by the transdermal and subcutaneous route, respectively. This detailed insight into the pharmacokinetics of moxidectin in bare-nosed wombats provides a crucial foundation for the design of treatment regimens, whilst also highlighting the inefficiency of transdermal delivery.