Selamectin

Selamectin, a semi-synthetic macrocyclic lactone, is a potent parasiticide and anthelminthic. Selamectin activates glutamate-gated chloride channels in neurons and pharyngeal muscles to prevent heartworm, Lymphatic filariae, and nematode infection. Selamectin is also a potent P-glycoprotein substrate and a P-glycoprotein inhibitor with an IC₅₀ of 120 nM^[1][2]. In Vitro: The transport of radiolabelled Selamectin through Caco-2 monolayers shows that Selamectin is P-glycoprotein (P-gp) substrates with a secretory/absorptive ratio of 4.7. Selamectin inhibits the efflux of Rh-123 from peripheral blood lymphocytes (PBL) and the concentration of inhibition is similar to that of Verapamil^[2]. In Vivo: A single administration of 6 mg/kg topical Selamectin given every two months could effectively prevent B. malayi infection in cats. Application of topical Selamectin twice a year could block circulating microfilariae^[1].