Viagra and other PDE5 inhibitors
Sildenafil (Viagra) revolutionized the way doctors treat ED, largely because it is effective and easy to use. But it is no longer the only drug option. Since 1998, when sildenafil became available, the FDA has approved a number of similar medications—namely, vardenafil (Levitra, Staxyn), tadalafil (Cialis), and avanafil (Stendra). And it has also approved a low-dose version of Cialis for daily use, creating an option that—theoretically, at least— makes having intercourse a possibility without advance planning. Another similar ED drug, udenafil (Zydena), is currently not approved for use in the United States, although it is available in a number of other countries.
All of these drugs—known medically as PDE5 inhibitors—work in a similar fashion. They block PDE5, an enzyme that breaks down the erection-producing chemical cyclic guanosine monophosphate. Without the enzyme to “shut off” erections, the penis fills with blood and stays erect long enough for intercourse. Of course, it’s important to realize that none of these drugs is an aphrodisiac. You must feel sexually aroused in order for them to work.
The main differences among the drugs have to do with how quickly they begin to work (onset), how long their effects last (duration), and how much they cost.
Onset and duration
One consideration in choosing an ED drug is how long you have to wait between taking the medication and having sex. Daily Cialis supplies a constant low level of the drug in your bloodstream, so you are always ready. With the other drugs, which are taken “as needed,” there is a wait time. Levitra may start working faster than Viagra (within a half-hour instead of an hour)—and Staxyn, which dissolves under the tongue, may work marginally faster than Levitra—although the FDA says that all of these drugs should be taken about an hour before sexual activity.
Note that the action of any of these medications may be delayed or impaired if you take them with food, especially high-fat foods. The delay is particularly noticeable with Viagra.
Another consideration is how long the effect lasts. The biggest advantage of nondaily Cialis is that it lasts the longest—24 to 36 hours, on average, which is why it’s sometimes called the “weekend drug.” Viagra and Levitra last about four to five hours (and sometimes as long as 12 hours), while Stendra lasts about six.