Viagra is a brand-name prescription medication available with the generic name Sildenafil. An oral drug for erectile dysfunction is the citrate salt of sildenafil, an inhibitor of cyclic guanosine monophosphate (cGMP) – clear phosphodiesterase type 5 (PDE5). Viagra is presented in blue, jewel-shaped, film-coated tablets containing 25 mg, 50 mg, and 100 mg Viagra for oral administration.