Viagra Science: Viagra Chemistry And Structure

Viagra: Chemistry and Structure

Sildenafil citrate, known commonly as the drug Viagra, gives a helping hand in treating male erectile dysfunction (impotence). The drug was developed by the pharmaceutical company Pfizer.

Viagra was initially developed to treat heart disease (angina) and the erection increasing effects came into the light during research trials. The drug was patented in 1996, approved by the FDA two year later on March 27, 1998 (becoming the first pill in the United States approved by the FDA to treat erectile dysfunction) and offered for sale in in the later part of the 1998.

Success of viagra in the market

As soon as Viagra entered the market it was a success. Even though Viagra is only available to patient by prescription, it was advertised directly on TV, radio and the internet. According to one estimate, annual sales of Viagra from 1999 to 2001 exceeded $1 billion.

Mechanism of viagra: how it works

Viagra works because the physiology of an erection involves the release of nitric oxide (NO) in the corpus cavernosum. This recharges the enzyme guanylate cyclase, which leads to enhanced levels of cyclic guanosine monophosphate (cGMP). The result is smooth muscle relaxation in the corpus cavernosum leading to enhanced inflow of blood to the point of engorgement, creating an erection.

Sildenafil is a potent, selective inhibitor of cGMP specific phosphodiesterase 5 (PDE5) that plays a prominent role in the degradation of cGMP in the corpus cavernosum. This means with Viagra, normal sexual stimulation results in enhanced levels of cGMP in the corpus cavernosum which leads to better erections. Sexual stimulation is required because without recharging of the NO/cGMP system, Viagra will not cause an erection.

Viagra is metabolized by hepatic enzymes and excreted by the liver and kidneys. If taken with a high fat meal, there may be some delay in the absorption of Viagra which can result in a decrease in effect because plasma concentrations are lowered. There are some reports that Viagra causes increased sexual pleasure for women by enhancing blood flow to the vagina.

Dosage and Price of FDA approved Viagra

Proper dosage is prescribed by your medical doctor. The dose of Viagra hovers around 25mg to 100mg daily, taken a half hour to 4 hours before sexual intercourse.

It is advisable to begin with a dosage of 50 mg and then increase or decrease the dosage over time. Viagra is sold in three dosages (25, 50, and 100 mg), all three costing about $10 per pill. Viagra is not scored, which means there is no guarantee that the drug is evenly distributed throughout the tablet, so it is not recommended to cut the pill to change its dosage.