# Pharmacokinetics and safety of topical fluralaner in koalas (Phascolarctos cinereus)

## TL;DR

This study shows that fluralaner, a parasite treatment, is safe and stays in koala blood for 12 weeks, potentially helping treat a harmful skin disease.

## Contribution

The study provides new pharmacokinetic and safety data for fluralaner in koalas, a species not previously studied with this drug.

## Key findings

- Fluralaner remained detectable in koala plasma for 12 weeks with a half-life of 30.91 days.
- The drug was well tolerated with no significant adverse effects observed.
- Fluralaner may be an effective treatment for Sarcoptes scabiei in koalas.

## Abstract

Sarcoptic mange (etiological agent Sarcoptes scabiei) is among the most important parasitic diseases of some marsupial species and has been an emerging disease of koalas, causing welfare and conservation implications. Fluralaner (Bravecto® MSD Animal Health), an ectoparasiticide of the isoxazoline class, has been demonstrated as a long-lasting and efficacious chemotherapeutic agent against sarcoptic mange in multiple mammal species and may also be beneficial for impacted koalas. Here, we evaluated the pharmacokinetics and clinical safety of fluralaner in koalas. Healthy captive individuals were treated topically with 85 mg/kg fluralaner administered to the interscapular epidermis. Following treatment, fluralaner was detected in plasma using ultra-performance liquid chromatography and tandem mass-spectrometry over a 12-week period. The mean maximum plasma concentration (Cmax) was 66.4 ng/mL; mean time was Cmax of 2.71 days; plasma elimination half-life (T1/2) was 30.91 days; and mean residence time (MRT) was 27.38 days. Haematological, blood biochemical, animal husbandry and clinical observations, over the same time period, demonstrated fluralaner was well tolerated. Overall, this research suggests fluralaner is a safe and long-lasting chemotherapeutic agent that may be efficacious against S. scabiei in koalas. Further research focussed on quantifying efficacy in captive and field settings, and across a range of disease severities would be valuable.

Image 1

•Koalas were treated with fluralaner that remained plasma-detectable for 12 weeks.•Standard safety measures demonstrate fluralaner was well tolerated.•Fluralaner is safe, and long-lasting and may be efficacious against Sarcoptes scabiei.

Koalas were treated with fluralaner that remained plasma-detectable for 12 weeks.

Standard safety measures demonstrate fluralaner was well tolerated.

Fluralaner is safe, and long-lasting and may be efficacious against Sarcoptes scabiei.