Viagra. Cialis. Levitra. These brand names for prescription oral phosphodiesterase type 5 (PDE5) inhibitors have become increasingly popular with men who suffer from impotence or erectile dysfunction, a condition marked by the ability to achieve and/or maintain an erection suitable for sexual intercourse. These drugs help the penile muscles to relax, thus allowing it to engorge and stay firm for a longer period of time. So with sexual stimulation, impotent patients can achieve erections. However, these so-called wonder drugs are not without side effects. Among the most commonly reported side effects are headache, muscle pains, vision disturbances, change in heartbeat (fast or slow), indigestion, nausea, vomiting, and flushing of the skin especially on the face and upper body.

While most patients are aware that taking nitrate-based drugs or alpha-blockers in combination with PDE5 inhibitors can be fatal, what most are unaware of is that these drugs also interact with certain foods. These drug interactions can be detrimental to the effects of the drug and can possibly cause serious damage to the patient. They can also aggravate the side effects of a drug they interact with. The most alarming part is that the most innocuous food items can be the cause of these drug interactions.

Take grapefruit juice, for example. It has been lauded in the medical community as a nutraceutical, or food that supposedly has health and medicinal benefits such as disease prevention. Some studies have concluded that the juice of a grapefruit contains chemicals that can reduce the risk of cancer and of atherosclerosis, or hardening of the arteries. Atherosclerosis has been linked to some cases of sexual impotence, and there are many impotent men who drink grapefruit juice for preventive and/or therapeutic purposes in conjunction with one of the PDE5 drugs. What they don't realize is that the effects of the medication are limited by the juice, and even make the side effects worse. Researchers believe this is because compounds in grapefruit juice called furanocoumarins block the enzymes that normally break down these drugs in the body, and this can last for up to 24 hours after ingestion.

This drug interaction was actually discovered accidentally by researchers when they used grapefruit juice to mask the taste of alcohol for their study, which was to see how an oral calcium-channel blocker called Plendil (felodipine) reacts to alcohol. They were surprised to find that in that particular trial, both the effects and side effects of the drug were amplified by the grapefruit juice because of the increased blood levels of felodipine. With further research, they were able to discover that the culprit was the juice itself and that it not only interacts with that specific drug but also with medications such as Viagra, Cialis and Levitra.

By amplifying the blood levels of these PDE5 drugs into toxic levels, grapefruit juice can impair the normal function or cause damage to vital organs. Because of the prolonged effect of the juice on the body, many doctors are now telling their patients to stop drinking it altogether if they are taking these medications daily. Be sure to ask your doctor for more information about drug interactions, because that information may actually save your life.