First of Two Viagra Rivals Is Approved for Sale.

Byline: Carey Goldberg

Aug. 21--The Food and Drug Administration has approved the first serious competition for Viagra, the little blue blockbuster that revolutionized the treatment of impotence -- and more rivals are on the way.

Levitra, a drug that combats erection problems in much the same way as Viagra but reportedly more quickly, taking effect in as little as 16 minutes, is expected to become available in pharmacies within weeks following the FDA approval late on Tuesday.

A third drug, Cialis, which also works similarly but lasts much longer, offering 36 hours or more of improved erections, is awaiting a final FDA decision late this year and could come to the US market within months, its makers say. Both drugs are already sold in Europe.

With Levitra and Cialis on their way and other impotence treatments under development, Viagra appears on the verge of losing its status as the only drug for the erectile dysfunction problems believed to affect some 30 million men in…