Gentlemen, fill your bathtubs. The Food and Drug Administration has approved a new daily version of the popular erectile dysfunction drug Cialis, advertisements for which have long featured a middle-aged couple perched in separate bathtubs atop a hill gazing dreamily at a panoramic view.

The initial formulation of Cialis, which was approved in 2003, took effect in about 30 minutes and lasted up to 36 hours. The version of the drug approved Jan. 8 removes the need for users or their partners to watch the clock before attempting to have sex.

Manufacturer Eli Lilly has said that the daily dose is aimed at men who want to have sex at least twice a week and those who place a premium on spontaneity. Because the new formulation remains in the userís system all day, there is no need to wait for it to work or worry that it might wear off. Lilly advises that users take the drug at the same time every day.

While Cialis, Levitra and the market leader, Viagra, are generally safe except for men taking nitrates, new warnings about rare cases of sudden hearing loss after using the drugs were added to their labels last year. The FDA asked drugmakers to add the warning after receiving about 30 reports of men who experienced the problem, sometimes accompanied by ringing in the ears or dizziness. In roughly a third of cases the hearing loss was temporary.

The agency advises men who experience such symptoms to stop taking the drug immediately and seek medical attention.