Cyclic guanosine monophosphate (CGMP) is responsible for smooth muscle relaxation of the intimal cushions of the helicine arteries. This leads to vasodilation and increased blood flow to the penis, causing an erection. CGMP levels are affected in part by degredation from CGMP-specific phosphodiesterase type % (PDE5.) Sildenafil is classified as a PDE5 inhibitor, and it works by protecting CGMP from PDE5. Sildenafil is broken down in the liver.

Sildenafil is thought to increase athletic performance in several ways. It has been shown to increase testosterone levels. Scientist, Matthew Spitzer, reviewed the effects sildenafil had on 140 men with low testosterone. He prescribed these men a dosage of sildenafil that varied based on several factors. The men who were on alpha-blockers received 25mg. The men who were receiving sildenafil for the first time received 50mg. The men that were regular users of sildenafil received 100mg. Spitzer observed the hormonal profiles of these men for 3-7 weeks. On average, total testosterone rose by 40 percent, free testosterone by 50 percent, and DHT levels also increased significantly. Elevated testosterone levels have a positive effect on strength and muscle mass. This will usually lead to an increase in performance among athletes.

When sildenafil allows blood vessels to relax and widen up, the increased blood flow and improved oxygen benefits go well beyond treating erectile dysfunction.

The effects this drug has in a low-oxygen environment have been studied and it has been found that the drug improves performance by improving exercise capacity. A 2006 study done at Stanford University claimed that sildenafil could improve an athlete’s 10-kilometer cycling time by 40 percent when used at an altitude of 12,700 feet. Cyclist, Andrea Moletta, was once found in possession of 82 sildenafil tablets and several syringes prior to the Tour of Italy, further fueling the suspicion of the drug’s use in sports to improve performance.

Sildenafil has been shown to increase the anabolic hormone, testosterone, and it has been shown to increase exercise capacity by improving blood flow to the lungs and increased oxygenation during endurance training and competition. Bodybuilders who may not be interested in endurance exercise, or the increased testosterone that sildenafil may offer, can still benefit from this drug. Nitric oxide supplements have become very popular among bodybuilders for their pump enhancing effects. Sildenafil works as a very potent vasodilator, and it is often used by bodybuilders before a workout for its ability to allow more blood flow to the muscles being trained. This allows for more nutrients to reach the muscle, and it enhances muscle growth. While sildenafil may have first been marketed to treat erectile dysfunction, its benefit goes well beyond the bedroom. Its use to improve athletic performance will probably soon become a common practice.