Viagra is the brand name of sildenafil, a blockbuster drug made by Pfizer. Originally developed for chest pain in the early 1990s, it hit the market in 1998 as a treatment for erectile dysfunction and garnered more than $1 billion in sales during its first year on the market, according to "Chemical and Engineering News." Celebrity pitchmen such as retired U.S. Senate leader Bob Dole and NASCAR driver Mark Martin kept the drug in the public eye. Effects of Viagra range from beneficial to undesirable.
Artery Expansion
Pub Meds Health explains that sildenafil belongs to class of medications called phosphodiesterase inhibitors, also called PDE inhibitors. Phosphodiesterase is an enzyme found primarily in the penis. It is responsible for breaking down the chemical that relaxes smooth muscle which allows the arteries to expand during an erection. When phosphodiesterase is inhibited, the chemical that allows arteries to expand is not broken down, thereby sustaining an erection for longer than normal.
Prevents Pulmonary Hypertension
A 2006 article in "Vascular Health Risk Management" explains that Viagra may be used in treating pulmonary hypertension due to cardiac surgery, left heart failure, fibrotic pulmonary disease, thromboembolic disease and high altitude exposure. Pulmonary hypertension is a particular type of hypertension that affects the pulmonary artery and veins. The authors suggest that sildenafil can be used either alone or in combination with other drugs to prevent pulmonary hypertension.
Clinical studies by Pfizer show that intravenous use of sildenafil resulted in a 28 percent decrease in pulmonary artery pressure.
Temporary Color Blindness
Clinical studies by Pfizer show that temporary color blindness can occur after a single 100 mg dose of Viagra. This is consistent with a common observation that everything looks bluish-green after taking the drug. Apparently, this side effect is related to the inhibition of PDE. Fortunately, this side effect resolves as the serum level of the drug drops.
