A 46-year-old woman with brown irides notices progressive darkening of one eye three months after starting latanoprost eye drops. She also reports mild anterior chamber flare on that side. Which property of latanoprost explains these findings?

• A It blocks melanocyte-stimulating hormone receptors in the iris stroma
• B It induces sympathetic denervation of the dilator pupillae
• C It stimulates melanogenesis in iris melanocytes through FP receptor activation ✓
• D It deposits prostaglandin metabolites within the anterior lens capsule

Explanation

Latanoprost activates prostaglandin FP receptors on iris melanocytes and upregulates melanogenesis, producing gradual, often irreversible darkening of the iris, most evident in mixed-colored eyes. Prostaglandin analogues can also provoke anterior uveitis and reactivate herpes simplex keratitis. The pigment change is increased melanin production, not receptor blockade or neural damage, and it typically affects the treated eye alone.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.