A medication that could be a faster-working alternative to Viagra and other erectile dysfunction drugs got approval from the Food and Drug Administration Friday.

The brand name you will be hearing in those inevitable ads: Stendra. It's made by a company called Vivus, Inc., and belongs to the same class of medicines as Viagra, from Pfizer Inc., Cialis, from Eli Lilly, and Levitra, from GlaxoSmithKline and Bayer. All inhibit the same enzyme, PDE5, and work by increasing blood flow to the penis.

About 30 million men have erectile dysfunction -- trouble getting or keeping an erection -- the FDA says.

The approval "expands the available treatment options" for such men and "enables patients, in consultation with their doctor, to choose the most appropriate treatment," FDA official Victoria Kusiak said in a statement.

The statement says patients will be instructed to take Stendra 30 minutes before sexual activity. But, in studies, the drug has been shown to work in as little as 15 minutes, which is faster than the 30 to 60 minutes reported for other drugs (though they have not been directly compared in studies).

The new drug will come with the same warnings as the others: 2% of patients in Stendra studies had side effects including headache, facial redness and nasal congestion, FDA says. In rare cases, patients may get an erection lasting four hours or longer that will not go away. Trouble with vision and hearing might also occur.

And, like the other drugs, it won't work for everyone: In Stendra studies, 57% of men with general erectile dysfunction and 40% of men with diabetes-related dysfunction were able to have successful intercourse.

Stendra, also is known as avanafil, could have $68 million in sales next year, Bloomberg reports. Viagra, the top-selling erectile dysfunction pill, had $2 billion in sales last year.

Meanwhile, Vivus is waiting for the FDA to rule on another one of its products -- a weight loss pill called Qnexa.