Described herein are stable veterinary formulations and methods of treatment and use, comprising at least one macrocyclic lactone and levamisole as active anthelmintic agents, optionally also with at least one benzimidazole class anthelmintic, wherein the actives are solubilized together in a solvent system comprising dimethylsulfoxide (DMSO). The veterinary formulations, methods and use thereof include the ability to deliver two or more anthelmintic actives in the one solution (or suspension) while also maintaining formulation stability when stored over a period of time. Delivery of different anthelmintics with different activities allows several classes of parasite to be targeted in one dose.
