Viagra 50mg 2 Tablets is a brand name for a drug called Sildenafil. The drug is used to treat erectile dysfunction and impotence in men & it is also used to treat pulmonary arterial hypertension. It works by enhancing the effects of nitric oxide, a chemical that causes blood vessels to relax and widen and increases blood flow to the penis during sexual stimulation. It also maintains a harder and stronger erection during sexual intercourse. Tablets are taken orally, usually as needed, about 30 minutes before sexual activity. The effect of this drug lasts for hours and it should not be taken more than once in 24 hours.