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).