United States Sildenafil is available as a generic drug in the United States, labeled for pulmonary arterial hypertension. Liver disease or reduced liver function may cause Viagra Sildenafil to build up in the body, causing side effects. Children: Viagra Sildenafil is not intended for use by children or adolescents under 18 years of age. Food and Drug Administration has approved fifteen drug manufacturers to market generic sildenafil in the United States. When choosing one, tell your doctor or other health care professional what your preferences are, such as cost, ease of use, how long the drug’s effects last and side effects. It added further: “As a matter of policy and sound statutory interpretation, patentees cannot be allowed to ‘game’ the system in this way.On November 8, , the Supreme Court of Canada invalidated Pfizer’s patent for blockbuster erectile dysfunction (ED) drug Viagra. The court ruled that in its patent, . Viagra (sildenafil) is a prescription drug that’s used to treat erectile dysfunction (ED). The drug comes as a tablet you’ll take by swallowing. It’s usually taken as needed about 1 . SAVINGS Terms and conditions apply. take any medicines called nitrates, often prescribed for chest pain, or guanylate cyclase stimulators like Adempas (riociguat) for pulmonary .