Bimatoprost is a medication that is primarily used to lower intraocular pressure in people with glaucoma. It has also been used off-label to promote the growth of eyelashes, leading to the development of bimatoprost eyelash serums. These serums are applied to the base of the upper eyelashes and are thought to increase the length, thickness, and darkness of lashes over time. Bimatoprost is a prescription medication, so it is important to speak with a doctor before using any bimatoprost-containing eyelash serums, as there may be potential side effects or drug interactions to consider.