The maker of the world's top-selling erectile dysfunction drug on Tuesday will begin airing the first Viagra TV commercial that targets the less-obvious sufferers of the sexual condition: women. In the new 60-second ad, a middle-aged woman reclining on a bed in a tropical setting addresses the problems couples encounter when a man is impotent. Having a woman speak directly to men about impotence is a unique strategy for Pfizer Inc. The world's second-biggest drugmaker is looking for ways to boost sales of Viagra, Pfizer's No. 6 seller, at a time when it is encountering new competition. Pfizer has seen generic competition for several of its other drugs cut revenue by billions, so it is hoping to stem the revenue losses for Viagra. Pfizer hope the new ad campaign, which includes print ads in publications such as Esquire and Time, will nudge women to broach the subject with their mates. Until now, women have been absent or played background roles in the many ads for ED drugs since the first, Viagra, was launched in 1998 and 50 million worldwide have taken it since then.