Viagra and Viagra both refer to sildenafil citrate tablets, which are the same medication that has a therapeutic effect on erectile dysfunction, and the effect of the medication varies from person to person. Sildenafil citrate tablets can promote penile erection and have a certain therapeutic effect on penile erectile dysfunction, and the effect of the medication will also vary depending on the existence of individual variability. The drug should not be used while taking any form of nitrates, guanylate cyclase agonists and other drugs, and should be prohibited in people who are allergic to the drug. Common adverse reactions to the medication include headache, nasal congestion, back pain, myalgia, hot flashes (bursts of fever), dyspepsia, abnormal vision, nausea, dizziness and rash. Specific medication should be directed by a specialist.