BOSTON (Reuters) - Allergan Inc, the maker of Botox, said on Friday that the U.S. Food and Drug Administration has approved its eyelash-thickening drug Latisse.

A model has her make-up applied backstage before the Kisa Spring/Summer 2008 collection show during London Fashion Week September 19, 2007. REUTERS/Luke MacGregor

Latisse is designed to treat a condition known as hypotrichosis of the eyelashes, which means a person does not have enough eyelashes.

The active ingredient in Latisse is bimatroprost, the same ingredient that is in Allergan’s glaucoma treatment Lumigan. Patients taking Lumigan found a side effect of the drug to be eyelash growth, prompting Allergan to study it for the new use.

Latisse is a once-daily prescription treatment that is applied to the base of the upper eyelash with a sterile, single-use-per-eye disposable applicator. Once treatment is stopped, eyelashes will gradually return to where they were prior to treatment.

Allergan said it estimates global peak sales of Latisse solution could top $500 million a year.

Gary Nachman, an analyst at Leerink Swann, said that while approval was expected, “in this cautious environment, every approval through the FDA should be viewed positively.”

Latisse is the first prescription product for lengthening eyelashes, making sales forecasting a little difficult.

Larry Biegelsen, an analyst at Wachovia, said he agrees with the company’s forecast of more than $500 million. However, “we think the initial uptake will be muted due to the economic situation.”

Biegelsen forecasts sales of $30 million in 2009, growing to $310 million in 2012.

Leerink Swann’s Nachman said he expects the drug to generate sales of $20 million in 2009, growing to $80 million in 2012.

“We believe the opportunity for Latisse could be much larger, but we still need to do more work on this largely unpioneered market,” he said.

Latisse is a structural prostaglandin analog, a lipid compound derived from fatty acids designed to bind to prostaglandin receptors. These receptors are present in hair and are thought to be involved in the development and regrowth of the hair follicle.

Side effects of Latisse can include eye redness, itchy eyes and a darkening of the eyelid skin. Though not reported in clinical studies, Allergan said Latisse may also cause the colored part of the eye to become browner, a condition that might be permanent.

Allergan said it expects to launch the product in the first quarter of 2009.

Allergan’s shares rose 1.1 percent to $36.85 on the New York Stock Exchange.