Travoprost: how does it work?

Travoprost appears to lower intraocular pressure (IOP) by increasing trabecular outflow facility, although an effect on uvoescleral outflow cannot be ruled out, according to a study published in the March issue of the Journal of Glaucoma.

Carol Toris and colleagues from the University of Nebraska Medical Center, USA, conducted a study to determine the mechanism by which travoprost 0.004% reduces IOP in patients with ocular hypertension or primary open angle glaucoma. The randomized, double-masked, placebo-controlled, single centre study enrolled 26 subjects.

After a washout of all medications, baseline IOPs were recorded and travoprost 0.004% was administered once-daily in the evening for 17 consecutive days to one eye and its vehicle to the fellow eye in a randomized, masked fashion. On day 15, twelve hours after the 14th dose, IOP was measured by pneumatonometry, aqueous flow and outflow facility by fluorophotometry and episcleral venous pressure by venomanometry. Uveoscleral outflow was determined by mathematical calculation. Two days later, the last drop was administered and fluorophotometry and tonometry measurements were repeated.

Eyes treated with travoprost demonstrated a significant decrease in daytime IOP (p<0.001) compared with baseline (26%) or to vehicle-treated eyes (22%), in addition to an increase in daytime outflow facility (p=0.001; 64%). The increase in uveoscleral outflow was not statistically significant. At night, travoprost-treated eyes remained 21-24% below baseline daytime values. Aqueous outflow was significantly reduced at night (p<0.001) in both travoprost (30%) and vehicle-treated eyes (25%) when compared with daytime values.

The researchers believe that travoprost works by increasing trabecular outflow facility, however, an effect on uveoscleral outflow cannot be ruled out.