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Erectile Dysfunction Drugs Vary in Effectiveness, Adverse Effects

Viagra (sildenafil) remains Number One

Viagra (sildenafil, Pfizer) is the most effective treatment for erectile dysfunction (ED), but it also has a higher rate of adverse effects than other options, according to an analysis of more than 150 studies.

Men concerned about the possible adverse effects of Viagra, such as headaches, flushing, indigestion, and nasal congestion, may want to start on Cialis (tadalafil, Eli Lilly), researchers report in European Urology. If that’s not effective, men in countries outside the U.S. can try Zydena (udenafil, Dong-A Pharmaceutical Company).

Many men have trouble getting or keeping an erection, especially as they age, but ED is not a natural part of aging, according to the U.S. National Institutes of Health.

The new review compares seven common ED therapies, all belonging to the phosphodiesterase 5 (PDE5) inhibitor class of medications. These drugs work by interfering with an enzyme that may reduce the potency of an erection. Viagra, Cialis, Levitra (vardenafil, Bayer HealthCare/GlaxoSmithKline), and Stendra (avanafil, Auxilium Pharmaceuticals) all work this way and are approved for use in the U.S. The additional drugs Zydena, Helleva (lodenafil, Cristália Chemical and Pharmaceutical Products), and Mvix (mirodenafil, SK Chemicals Life Science) are approved only for use in other countries.

PDE5 inhibitors are considered first-line therapy for ED, but they are effective in only 60% to 80% of men who try them, and many will stop taking them, according to Dr. Alexander W. Pastuszak of Baylor College of Medicine, who was not part of the new study.

Researchers at the University of Zurich, the Swiss Federal Institute of Technology, and Maastricht University Medical Center in the Netherlands reviewed 82 studies of PDE5 inhibitors in subjects with ED and 72 studies exploring the drugs’ adverse effects.

These treatments were all more effective than placebo for treating ED and were generally safe and well tolerated, the authors reported.

A 50-mg or 100-mg dose of sildenafil appeared to be the most effective treatment. It performed about 50% better than placebo. Smaller doses were less effective. Avanafil, in doses ranging from 50 mg to 200 mg, was among the least effective –– only 20% to 30% better than placebo.

The 50-mg dose of avanafil was associated with the lowest rate of adverse effects of any medication (8.5%). A 20-mg dose of vardenafil had the highest rate of adverse effects (25%). Higher doses of sildenafil and tadalafil tended to cause adverse effects 21% and 22% of the time, respectively.

One of the main adverse effects of Viagra is visual changes, whereas Cialis more often causes muscle pain. In general, PDE5 inhibitors can cause a steep drop in blood pressure because they are vasodilators. For this reason, PDE5 inhibitors should not be used with nitrate-based heart medications. Other common adverse effects include facial flushing, congestion, headache, and upset stomach.

Urologists already have an understanding of the effectiveness and adverse effects of the available ED therapies, so the new results will not be a surprise, Pastuszak said. Only Cialis is to be taken daily; the other options are all short-acting, so men have the option of trying several to see which one works well, he said.

Doctors should carefully discuss expectations and treatment effects of the various options with ED patients before choosing a therapy, the authors write. Some patients may want immediate stronger efficacy at the cost of more-severe adverse effects, while others may not.

Sources: Reuters; April 7, 2015; and European Eurology; March 26, 2015.

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