The erectile dysfunction marketplace could get its first new entry in almost a decade with the experimental drug Avanafil, a faster-acting pill in the same class as Viagra, Levitra and Cialis, reportedly with fewer side effects.

But do we really need another Viagra?

"No, we don't need another Viagra, but competition is good. We need to see a reduction in the cost to the consumer of these drugs, and this is not exactly another Viagra," said Dr. Ira Sharlip, a urology professor at UC San Francisco and former president of the International Society for Sexual Medicine. "I say this because the onset of action seems to be faster than Viagra, although there are no head-to-head studies of onset of action."

The little blue pill Viagra (sildenafil) started a late 20th century sexual revolution by destigmatizing impotence, and replacing that term with "erectile dysfunction," or ED in the popular lexicon. Like Viagra and its competitors Levitra (vardenafil) and Cialis (tadalafil), all of which are regularly advertised on television, Avanafil increases blood flow to the penis to help men achieve and sustain an erection. But its main selling point may be that clinical trials suggest it can produce an erection in as little as 15 minutes.

"Quick onset of action is important to men," especially a subset of patients seeking treatment for erectile dysfunction, Sharlip said.

"Men who have a pattern of sexual activity that's predictable - every Saturday night, or something like that, don't need this. Those whose opportunities for sexual activity are more casual will like it," Sharlip predicted. "If you see that things are heading in that direction, you pop a pill and are ready in 15 minutes, if  correct."

The studies also indicate Avanafil clears the body more quickly than the other ED drugs in the same class, the phosphodiesterase type 5 (PDE5) inhibitors, according to data submitted to the FDA by Vivus Inc. The pharmaceutical company also is behind the diet drug Qnexa, which remains under FDA review.

In a Phase II study, Avanafil worked as well as Viagra while producing less low blood pressure in cardiac patients who take nitroglycerin. In the two Phase III trials that compared Avanafil with a placebo, there were no reports of blue vision or prolonged, painful erections (priapism), which are infrequent side effects associated with Viagra. In rare cases, men taking any of the PDE5 drugs have reported sudden decreases in hearing or loss of hearing.

Sharlip said he didn't believe that those rare side effects matter much to most patients. "Despite what the FDA says, I have never seen priapism from any PDE5 inhibitor drug. Priapism is just not a clinical problem. Blue vision with Viagra is uncommon and at worst annoying. Most men who get the blue vision with Viagra don't care about it," he said.

The most common side effects of Avanafil in studies to date were headache, flushing, stuffy nose, mild cold symptoms and back pain.

Avanafil has been approved for use in Korea.

The FDA set an April 29 target date for its Avanafil review. Vivus, based in Mountain View, Calif., licensed rights to the drug from Mitsubishi Tanabe Pharma Corp.

The most recent FDA approval of an ED drug came in 2010 for Staxyn, a version of vardenafil that dissolves under the tongue, rather than being swallowed.