Neurological adverse effects of isoxazoline exposure in cats and dogs

Isoxazolines are rarely reported to be associated with neurological adverse events in cats and dogs, but information about the onset and duration of neurological signs is lacking in the summary of product characteristics of these medicines.

The Veterinary Poisons Information Service and the Dutch Poisons Information Center databases were searched using the Veterinary Dictionary for Drug-Related Affairs terms for ataxia, muscle tremor, convulsions or hyperesthesia in cats and dogs exposed to isoxazolines.

There were 22 cases with and 57 cases without outcome information, mostly involving fluralaner or sarolaner. In both groups, muscle tremors and convulsions were the most common signs. In dogs, neurological signs occurred with oral therapeutic dose and overdosage. In cats, most fluralaner cases involved therapeutic topical exposure, and all sarolaner cases involved oral exposure. In all cases with outcome information, the animals recovered.

Cases discussed with poison centres tend to involve more severe signs.

The true incidence of neurological adverse effects from isoxazolines remains unclear. The delay between the administration and onset of signs can be long, and the association may be missed. A lack of timing information in the summary of product characteristics could also contribute to missed attribution of adverse effects.