Allergan Inc's drug bimatoprost increased the length, thickness and darkness of eyelashes in a company study, U.S. drug reviewers said in a report released on Wednesday.

The analysis was prepared for a Food and Drug Administration advisory panel that meets Friday. The panel will be asked whether the benefits of bimatoprost for eyelash growth outweigh its risks, the FDA staff report said.

Four out of 137 patients who used the drug, which was applied daily along the upper eyelid, dropped out of the study because of mild or moderate eczema, dry eye, eye inflammation or dermatitis, FDA staff said.

In a separate summary, Allergan said problems reported by users "occurred at a low frequency and were largely mild in severity, cosmetic in nature, and reversible."

"The overall benefit-risk assessment of bimatoprost for eyelash growth is favorable due to the fact that risks are minimal and the aesthetic benefits are well-demonstrated and meaningful," the company said.

Allergan, the maker of the wrinkle-filler Botox, estimates global peak sales for the eyelash drug could top $500 million per year. The proposed brand name is Latisse.

The drug, which would be sold by prescription, is a formulation of Allergan's glaucoma treatment Lumigan.