The present invention relates to highly selective phosphodiesterase (PDE) enzyme inhibitors and to their use in pharmaceutical articles of manufacture. In particular, the present invention relates to potent inhibitors of cyclic guanosine 3',5'-monophosphate specific phosphodiesterase type 5 (PDE5) that when incorporated into a pharmaceutical product at about 1 to about 5 mg unit dosage are useful for the treatment of sexual dysfunction.