Long-acting spiro-isoxazoline antiparasitic compositions

A long-acting topical composition comprising:

• a) a spiro-azetidine that is 1-(5′-(5-(3,5-dichloro-4-fluorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)-3′H-spiro[azetidine-3,1′-isobenzofuran]-1-yl)-2-(methylsulfonyl)ethenone, or a stereoisomer thereof;
• b) a glycol ether selected from the group consisting of diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether and diethylene glycol dimethyl ether;
• c) at least one veterinarily acceptable solvent selected from the group consisting of dimethyl isosorbide, caprylic/capric triglyceride, propylene glycol laurate, isopropyl myristate, oleic acid, eucalyptol, benzyl alcohol, benzyl benzoate, ethanol, propylene glycol caprylate, caprylocaproyl macrogol-8 glyceride and isopropanol, or any mixture thereof;
• d) optionally, at least one precipitation inhibitor;
• and
• e) optionally, at least one antioxidant.