Methods for treatment of sexual dysfunction in men and women using combinations of phosphodiesterase (PDE) type 5 inhibitors and l-deprenyl or propargylamine compounds are described. Methods of reducing the dosage and preventing the side effects of PDE type 5 inhibitors are also described. The methods comprise administering a therapeutically effective amount of l-deprenyl or propargylamine compounds (also called monoamine oxidase [MAO] inhibitors) in combination with PDE inhibitors. Stimulation of nitric oxide production and vasodilation by l-deprenyl and propargylamine compounds augments the actions of PDE inhibitors or other drugs and methods used in the treatment of sexual dysfunction. The composition described here enhances the actions of PDE inhibitors primarily by increasing the generation of cyclic GMP by stimulating the nitric oxide pathway and secondarily by providing several additional benefits such as enhanced dopamine activity. Methods of enhancing the efficacy of various PDE inhibitors in the treatment of a number of disorders other than sexual dysfunction are also disclosed.