New sex-aid drug's effects lasts longer

The latest drug approved for treating erectile dysfunction, tadalafil (Cialis), has been dubbed the “weekender” because it’s effective up to 36 hours, compared with the 4-hour duration of its competitors, sildenafil (Viagra) and vardenafil (Levitra). That allows couples more leeway in choosing when to have sex, though whether or not more than one encounter per dose will be successful has not yet been studied, ads say. The drug’s prolonged efficacy may become a liability, however, if the drug causes adverse effects or interacts with other drugs.

All three medications work by dilating blood vessels, particularly in the penis, thereby increasing the blood flow needed to create an erection when there’s enough stimulation. And they are all effective for about three-fourths of users.

The three drugs have not been compared directly. But in separate clinical trials, tadalafil was the only one more likely than a placebo to cause muscle aches and back pain--although those side effects rarely caused participants to stop using the drug. Like other long-lasting medications, any side effects of tadalafil are likely to persist longer than those of the other drugs. And less is known about tadalafil’s long-term safety than sildenafil’s. On the plus side, tadalafil appears to be much less likely to cause the “blue vision”--a temporary shift in color perception--experienced by 2 to 3 percent of sildenafil and vardenafil users.

Like the other drugs, tadalafil should not be used by men who have a high risk of heart attack or stroke. It should also be avoided by those who take nitrates, such as isosorbide (Isordil, Nitrobid), to treat angina, and those who take alpha-blockers, such as prazosin (Minipress) and terazosin (Hytrin), to treat hypertension or prostate symptoms. One exception: Studies show that tadalafil can be taken safely with up to 0.4 milligrams per day of the alpha-blocker tamsulosin (Flomax).

For now, our medical consultants recommend sticking with sildenafil whenever possible, since it has the longest safety record. Men who opt for the increased convenience of tadalafil should understand that they may face longer-lasting or unknown adverse effects.