The present invention relates to highly selective phosphodieterase (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 20 mg unit dosage are useful for the treatment of sexual dysfunction.