Sep

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How does Viagra (sildenafil citrate) pill work?

Filed Under VIAGRA, How Viagra Works

Overview

Viagra (sildenafil citrate) is a medication that works by increasing blood flow to the penis. Viagra enables many men with erectile dysfunction (impotence) problem to respond to sexual stimulation. When a man is sexually excited, Viagra helps the penis fill with enough blood to cause an erection. After sexual activity is over, the erection goes away.

Detailed Medical Explanation

Viagra is used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH). Part of the physiological process of erection involves the release of nitric oxide (NO) in the penile corpus cavernosum. This then activates the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation in the corpus cavernosum, resulting in increased blood flow to the penis and an erection. Viagra is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. This means that, with Viagra on board, normal sexual stimulation results in increased levels of cGMP in the corpus cavernosum which leads to better erections. Without sexual stimulation and no activation of the NO/cGMP system, Viagra should not cause an erection.

Viagra inhibits the cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum located around the penis. Penile erection during sexual stimulation is caused by increased penile blood flow resulting from the relaxation of penile arteries and corpus cavernosal smooth muscle. This response is mediated by the release of nitric oxide (NO) from nerve terminals and endothelial cells, which stimulates the synthesis of cGMP in smooth muscle cells. Cyclic GMP causes smooth muscle relaxation and increased blood flow into the corpus cavernosum. The inhibition of phosphodiesterase type 5 (PDE5) by Viagra enhances erectile function by increasing the amount of cGMP.

Mechanism of Action