Viagra

sildenafil citrate

How the most popular drug of all time works

Pfizer, Inc., claims that its erectile dysfunction drug Viagra is so popular that nine pills are dispensed every second. When it works as intended, it enables a man who is sexually stimulated to get and maintain an erection. It does this by relaxing the smooth muscles in walls of arteries that bring blood flow to the penis. In patients with erectile dysfunction, the muscle walls do not relax and the arteries remain constricted. Erectile dysfunction drugs work to relax those muscles by selectively blocking the enzyme PDE5 (phosphodiesterase5) that controls arterial constriction in the penis. Relaxed arterial walls then enable pressurized blood to enter the penis.

Since its introduction in 1998, more than 23 million men have been prescribed Viagra for erectile dysfunction. One of the most heavily marketed prescription drugs of all time, patients who take Viagra can even get a discount program card called the Viagra Value Card which provides them with one free refill for every six prescriptions filled.

Viagra Side Effects

Sildenafil citrate, the active ingredient in Viagra, controls PDE5 but it has a spill-over effect: it also controls PDE6, which is an enzyme that controls blood flow in the retina. Some people who take Viagra may experience changes in their color vision. They may see their environment in shades of blue or green instead of many colors.

Viagra can also open up arteries in the brain’s lining and cause excess pressure to build up, resulting in headaches. There is also a possibility of heart attack with taking Viagra in patients at risk for cardiovascular events. Now Viagra has recently been linked to a serious adverse event known as nonarteritic ischemic optic neuropathy (NAION), or “stroke to the eye.” Over 35 patients have suffered NAION after taking Viagra, which results in permanent partial or even total blindness in one or both eyes. Despite increasingly alarming reports of vision problems in patients, Pfizer, Inc., manufacturer of Viagra, continues to state that Viagra is a safe prescription drug.

Viagra linked to NAION in 38 patients

For years it’s been known that Viagra can cause a small number of patients to experience color changes and blurring in their vision. They may see things as shades of blue or shades of green. These vision changes may be a sign that a patient is at risk for NAION, because a low cup to disk ratio might be responsible for those vision changes.

Viagra regulates a chemical in the body to constrict the arteries. This constriction may cut off the blood flow, provoking NAION and causing blindness. Fourteen patients who suffered permanent blindness exhibited NAION within 36 hours after ingestion of Viagra.

In October 2007, the United States Food and Drug Administration (FDA) mandated label changes on erectile dysfunction (ED) drugs, including Viagra, to include the potential risk of sudden hearing loss.