Viagra is the leading drug for impotence, with worldwide sales of $1.7 billion

Pfizer boasts that nine Viagra pills are popped every second and soon users in the U.S. will have some new options.

The Food and Drug Administration approved Levitra last week as a treatment for impotence. The drug from GlaxoSmithKline and Bayer, works pretty much as Viagra does, increasing blood flow to the penis and reducing muscle relaxation.

Viagra begin working within 30 minutes (although some say Levitra works sooner), both last four to five hours, and both are effective nearly 70% of the time.

Both Levitra and Viagra also share side effects, which include headaches, nasal stuffiness and stomach upset.

But for those who consider a romantic dinner an important part of foreplay, Levitra offers one advantage: it can be taken with food, whereas Viagra requires an empty stomach.

Eli Lilly's Cialis has the distinction of remaining effective for up to 36 hours. In Europe, where it is already in use, it has been fondly dubbed the weekender.

Nearly 30 million men in the U.S. suffer from impotence and remarkably, only 1 in 5 seeks treatment such as Viagra and many who do are disappointed.

"A little more than half the men drop out of Viagra therapy, and probably a third don't get the effect they want," says Dr. Irwin Goldstein, director of Boston University's Institute for Sexual Medicine, "so there is room for options."

About 85% of impotence is due to such physical ailments as heart disease, prostate cancer and diabetes. Some 10% of cases have a psychological basis; the rest are unexplained. If you think you've seen enough ads dealing with this delicate issue, brace yourself.

The folks bringing you Viagra have recruited former NFL star and coach Mike Ditka for a broad promotional campaign called "Tackling Men's Health." The manly ads roll out with the start of football season.

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