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How do Viagra, Levitra and Cialis treat erectile dysfunction (ED)?

Marc B. Garnick, MD
Hematology & Oncology
Sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) belong to a class of drugs called PDE5 inhibitors. They are easy to use and have proved effective for erectile dysfunction (ED), helping 60% to 70% of men who take them. They can be effective in treating ED related to radiotherapy for prostate cancer, nerve-sparing radical prostatectomy, and BPH medications. PDE5 inhibitors aren't useful for treating ED that follows non-nerve-sparing or unsuccessful nerve-sparing radical prostatectomy, probably because they work on the same nerves that are destroyed or damaged during surgery. Even if the nerves are preserved, PDE5 inhibitors are usually ineffective during the first six months after surgery or radiation therapy.

Despite some impressive results, PDE5 inhibitors have their limitations. They're expensive, and some health insurance plans don't cover them or cover just a few pills per month. Also, they shouldn't be taken more than once a day. You should not take these drugs if you are taking nitrates. Men who take certain alpha blockers that tend to lower blood pressure also need to exercise caution. Indeed, all men with heart disease should take care with these drugs because of their tendency to lower blood pressure. If you take an ED drug and go to the hospital with heart attack symptoms, it's imperative that you tell the health care team that you've taken this drug.

Short-term side effects may include headache, flushing, upset stomach, and nasal congestion. Temporary disturbances in color vision have also been reported. Another possible though relatively rare complication is priapism, an erection that lasts too long. Any man who has an erection for more than four hours should go to the emergency room to receive a counteracting drug. Not doing so could result in permanent impotence.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.