The invention describes a long-acting injectable veterinary composition comprising a spirocyclic isoxazoline, at least one biopolymer, and optionally, at least one veterinary acceptable-carrier, -solvent, -excipient, or any mixture thereof. The invention also includes a method of treating an animal with a parasitic infestation by administering the biopolymeric composition to the animal in need thereof, and a process for preparing the biopolymeric composition.
