Viagra is the trade name and generic name for sildenafil citrate tablets, the effectiveness of sildenafil citrate tablets generally varies from person to person, with a common dose of 50 mg taken approximately one hour before sexual activity. Sildenafil citrate tablets are generally indicated for patients with erectile dysfunction. Sildenafil is part of the first generation of phosphodiesterase type 5 inhibitors. It is absorbed relatively rapidly after oral administration, and food has an effect on its absorption, so it needs to be taken on an empty stomach, and the effect of the drug lasts for about 0.5 to 4 hours. However, this drug may cause adverse reactions such as dizziness and headache after taking it, and it should not be used in children or women. Patients with epilepsy and heart disease with a history of epilepsy should use the drug with caution. Patients using nitrate drugs are also not able to use sildenafil tablets at the same time. Patients with cavernous fibrosis and penile curvature should also not use sildenafil. The above drugs are for reference only, the specific dosage should follow the doctor’s instructions. Do not adjust the dosage on your own to avoid adverse reactions.