Sildenafil Pack to Treat Impotence in Men is a drug that specifically treats Erectile Dysfunction (ED) and Pulmonary Arterial Hypertension (PAH). It is sold under the brand names of Viagra and Revatio. It works by preventing cGMP-specific phosphodiesterase type 5 (PDE5) which is an enzyme that causes the degradation of cGMP. It is also responsible for regulating the flow of blood in the penis. Today, it is the major treatment of ED.