Tablets uk prices sildenafil affects the response to sexual stimulation. It acts by enhancing smooth muscle relaxation using nitric oxide, a chemical that is normally released in response to sexual stimulation. This smooth muscle relaxation allows increased blood flow into certain areas of the penis, which leads to an erection. Usually, the recommended dose is 50 mg. It is taken approximately 0,5-1 hour before sexual activity. Do not take Viagra more than once a day. A high-fat meal may delay the time of the effect of this drug. Try not to eat grapefruit or drink grapefruit juice while you are being treated with Sildenafil Citrate.