Disclosed is a solvent based topical formulation containing a macrocyclic lactone and a levamisole active ingredient dissolved in one or more organic solvents selected from the group comprising dimethyl acetamide, dimethyl isosorbide, diethyl phthalated, dimethyl phthalate and glycol ethers, and which further contains a viscosity modifier sufficient to increase the viscosity of the formulation to give it significant resistance to running.
