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Ask Dr. K: Erectile dysfunction drugs are all about timing

DEAR READER: Erectile dysfunction (ED) is a problem faced, to one degree or another, by many middle-aged and older men. Since sildenafil (Viagra) was launched in 1998, men have been turning to medication to help address this problem.

There are currently four ED drugs on the market: sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) and avanafil (Stendra). These drugs all work the same way: They lead to increased production of a chemical that causes blood flow into the penis to rise. Inside the penis is a spongy tissue. Like a sponge, when it fills with fluid it swells. The increased blood flow into the penis causes the “sponge” to swell and the penis to stay erect long enough for intercourse.

The main difference among the drugs has to do with timing — how quickly they begin to work and how long their effects last. How soon the drugs start working ranges from 15 to 60 minutes. The onset time determines how soon you can engage in intercourse. (I’ve put a table on my website, AskDoctorK.com, listing the onset times and durations for the available ED drugs.)

Viagra and Levitra last about four to five hours (and sometimes up to 12 hours), while Stendra lasts about six. Cialis stays active in the body much longer than the other drugs; the window of opportunity ranges from 24 to 36 hours. (That’s why it’s sometimes called the “weekend drug.”) Another version of Cialis, approved for daily use, keeps a steady supply of the drug in the bloodstream. It allows a man to be prepared for sex at any time.

Neither Viagra nor Levitra will work if you take either after a meal, as food blocks their absorption. Neither Cialis nor Stendra interacts with food this way.

Doctors usually offer sildenafil (Viagra) first. It’s been on the market longest, and its side effects and the medications and foods it interacts with are well known.

So far, the risks and side effects of all of these drugs seem to be roughly the same. So if Viagra doesn’t work for you, you might have better luck with one of the others.

The ED drugs have brought happiness to many couples. However, they don’t always work. If a man has no sexual desire, or is on medicines that cause ED as a side effect, the ED drugs may not work. Severe blockage of the blood supply to the penis from atherosclerosis of the arteries leading to the penis also can interfere.

Men may also be anxious about their “performance.” Or they may have heart disease and be afraid that the physical exertion of sex will trigger heart problems (it rarely does). Or, finally, they may be anxious because they are having sex with someone other than their spouse.

Nevertheless, the drugs work more often than not. Your choice among them is something you should discuss with your doctor.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.

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