Viagra is generically known as Sildenafil Citrate, and there is no such thing as topical Sildenafil Citrate; this medication is generally available in tablet form and is an oral medication. Sildenafil citrate is a type 5 phosphodiesterase inhibitor that is currently used to treat erectile dysfunction in men, and is commonly available in tablet form. Nitric oxide is released in the cavernous body of the penis during sexual stimulation, and nitric oxide activates guanylate cyclase, which can increase the level of cyclic guanosine monophosphate, relax the smooth muscle in the cavernous body, and promote blood inflow. Some patients may experience adverse reactions such as headache, dyspepsia, muscle pain, nausea, and dizziness while taking sildenafil citrate. It should be contraindicated for people who are allergic to the ingredients of Sildenafil Citrate, people taking nitrate drugs, women, children and other people. If the patient is taking Sildenafil Citrate, the body abnormal discomfort, it is recommended to go to the regular hospital in time, so as to clarify the cause of the disease. In daily life, you should have a regular routine and avoid prolonged exertion. Maintain a positive attitude and avoid negative emotions. Drugs should be applied under the guidance of a doctor.