Viagra generally refers to sildenafil. The benefits of taking this medication include treatment of erectile dysfunction and pulmonary hypertension, while the disadvantages include symptoms such as headaches and indigestion after use. 1. Benefits: Sildenafil is a type 5 phosphodiesterase inhibitor, which inhibits this enzyme on vascular smooth muscle and acts as a vasodilator. It can act on the cavernous body of the penis and the pulmonary vessels and is used to treat diseases such as erectile dysfunction and pulmonary hypertension. 2. The bad: Sildenafil generally has no significant side effects, the more common are symptoms such as headaches. When dilating blood vessels in the brain, it can pull on the nerves to cause headaches, which can usually be relieved on their own after stopping the drug. The drug should be used under the guidance of a professional doctor to avoid the adverse consequences of self-medication. If any discomfort occurs after use, you should go to the hospital in time.