Last year, sildenafil's 5-year reign as the unchallenged king of erectile dysfunction treatment came to an end when both vardenafil and tadalafil came onto the U.S. market.
Before sildenafil's approval in 1998, drug treatment of erectile dysfunction (ED) was limited to alprostadil (prostaglandin [E.sub.1]), either injected into the penis or inserted as a pellet into the urethra. Understandably, an oral agent to treat ED had considerable impact. In 1997, only 1.7 million of the 30 million American men with erectile dysfunction sought treatment. After sildenafil was approved, treatment numbers soared to between 6 million and 7 million annually. That number, however, still represents only a fraction of men with ED.
Sildenafil, vardenafil, and tadalafil are all potent, selective inhibitors of phosphodiesterase type 5 (PDE-5). Although they work by the same mechanism, they are not the same in all respects. The differences in their interactions with [alpha]-blockers are small but potentially significant. Sildenafil and vardenafil are virtually identical in efficacy and duration of action. Side effects are also similar, except that vardenafil, a slightly more selective PDE-5 inhibitor, is somewhat less likely to cause the uncommon side effect of transient visual disturbance. Tadalafil, with a more prolonged postdose efficacy of up to 36 hours, may better suit some patients.
Patient preference can help guide the choice of drug. A frank and detailed discussion of the patient's sexual habits, preferably with his partner present, can help determine which drug to try first. Some partners don't like the time-dependent nature of vardenafil and sildenafil and resent what they feel is their partner's sexual response to a pill rather than to them. It's important to remind both patients and partners that the PDE-5 inhibitors don't cause automatic erections; sexual stimulation is also necessary. And patients should understand that nondrug therapy, with vacuum or an implant, is also an option.
Men need to understand the importance of adopting healthier lifestyles, including losing weight and giving up cigarettes. Men who have resisted advice about smoking and weight loss may react differently when they learn that cigarettes and obesity can contribute to impotency. Men who must avoid sexual activity because of their cardiac status should not use any of these drugs or other treatments for ED.
The PDE-5 inhibitors are effective in healthy elderly men with ED, but clear more slowly. In elderly patients, the initial dosage should be half the usual recommendation and then titrated up as needed and tolerated.
Men who can't tolerate any PDE-5 inhibitor or who are among the 20%-30% who don't respond can try alprostadil in injection or pellet form. The injectible form helps 80% of men with ED, including 10% of those who don't respond to oral agents. A much smaller percentage respond to the pellet form.
Trimix, another injectable therapy, induces erections in all men except those with severe vascular disease or venous leakage. Trimix is an off-label mixture of three Food and Drug Administration-approved drugs: papaverine, phentolamine, and alprostadil. The mix must be prepared by a pharmacist.
Editor, Mitchel L. Zoler
Writer, Michele G. Dabney Professor ofSullivan
COPYRIGHT 2004 International Medical News Group
COPYRIGHT 2004 Gale Group
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