Viag treats erectile dys function and works by relaxing muscles and increases blood flow to particular areas of the body (in this case, the penis, specifically). Its effects last up to four hours. The most common side effects of Viag are headache, facial flushing, and upset stomach. Rarely, blurred vision, or sensitivity to light may briefly occur.

As well as treating impotence, Sildenaf Citrate can also be effective in treating Pulmonary Arterial Hypertension (PAH). Similarly to how it acts to relax muscles of the penis, it relaxes arterial walls; therefore, reducing resistance and pressure in the arteries.