isoxazolines

Isoxazolines are a widely used class of ectoparasiticides for companion animals, including dogs and cats. They consist of a heterocyclic compound containing an isoxazoline ring and act as ligands that inhibit GABA- and glutamate-gated chloride channels in arthropods, causing hyperexcitation of neurons, leading to paralysis and death of fleas, ticks, and certain mites. The compounds show selective toxicity due to differences in the receptors between invertebrates and mammals, resulting in a favorable safety profile in treated animals.

Commercially, isoxazolines are formulated as oral tablets or chewables, and in some cases as topical solutions; examples include afoxolaner, fluralaner, lotilaner, and sarolaner. They provide systemic protection by circulating in the bloodstream, killing parasites that feed on the host. Their activity is generally long-acting, with monthly dosing schedules common and some products offering extended protection for specific tick species.

Safety: In controlled use, isoxazolines are well tolerated in most dogs and cats. Reported adverse events are usually mild and transient, such as vomiting, diarrhea, lethargy, or in rare cases neurologic signs including tremors, ataxia, or seizures, particularly in animals with preexisting conditions or concurrent medications. As with all parasiticides, there is ongoing monitoring for rare adverse reactions and potential drug interactions.

History and regulation: Isoxazolines were developed and marketed by several pharmaceutical companies in the 2010s for veterinary use. They are approved for use in many countries for dogs and cats and are not approved for use in humans. Ongoing surveillance addresses efficacy, safety, and the potential development of resistance in parasite populations.