Mechanism of action of bimatoprost (Lumigan).

Bimatoprost is a new ocular hypotensive agent that lowers intraocular pressure (IOP) in normal, ocular hypertensive, and glaucomatous eyes. Its mechanism of action has been studied in normal human subjects. Bimatoprost mildly stimulates the rate of aqueous humor flow during the day (13%) and at night (14%). Its ocular hypotensive action is due primarily to a 26% reduction in the tonographic resistance to outflow. Thus, bimatoprost enhances the pressure-sensitive outflow pathway. Additional beneficial effects may include an increase in the rate of flow via the pressure-insensitive outflow pathway (sometimes called the "uveoscleral outflow pathway") and a lowering of the extraocular recipient pressure (sometimes called "episcleral venous pressure"). Reduction of tonographic resistance to aqueous humor outflow reduces steady-state IOP, an effect that is beneficial for the treatment of glaucoma. In addition to its effect on steady-state IOP, reduction of resistance allows the eye to recover more quickly from transient IOP elevations. The former effect is common to all ocular hypotensive drugs, but the latter effect is an exclusive property of drugs that reduce outflow resistance, such as bimatoprost.