The discovery that latanoprost eye drops caused eyelash thickening in glaucoma patients led to one of dermatology's more interesting drug development stories. Allergan repurposed bimatoprost as Latisse, the first FDA-approved treatment for inadequate eyelash growth. The mechanism, prostaglandin F2-alpha receptor agonism extending anagen phase and stimulating dermal papilla proliferation, has obvious scalp implications, and multiple groups have explored prostaglandin analogues for androgenetic alopecia.

The clinical data for scalp application is mixed. A 2013 study of 0.1% latanoprost solution on the scalp showed modest hair density improvements over 24 weeks (approximately 7 additional hairs/cm² versus vehicle). Larger trials with bimatoprost solution for scalp use produced more disappointing results, Allergan's PROSTHER trial in 2019 was discontinued for inadequate efficacy. The likely explanation involves differential receptor expression: scalp follicle receptor density appears insufficient for the response seen on eyelid follicles.

Newer prostaglandin-pathway drugs are in development for scalp use, including more potent and selective receptor agonists, with the goal of overcoming the receptor density limitation. The hair loss field is also revisiting the PGD2 receptor antagonist approach (setipiprant) for a complementary mechanism, blocking the inhibitory prostaglandin while potentially layering a stimulatory one. As a current option, scalp-applied latanoprost is occasionally compounded by specialty pharmacies but evidence remains too thin to recommend widespread use.