research digest

Patient Persistence Greater With Latanoprost vs. Other Agents

Three recently published studies demonstrated that patients taking latanoprost (Xalatan) were more likely to persist with their monotherapeutic regimen longer than those receiving other hypotensive medications, including rival prostaglandin-type agents.

Reardon et al. conducted a population-based retrospective cohort study involving 2,850 glaucoma patients started on betaxolol (Betoptic), brimonidine 0.2% (Alphagan), dorzolamide (Trusopt), latanoprost (Xalatan) or timolol (Timoptic) between May 1999 and January 2001. Discontinuation or change of regimen were the primary outcome measures. Those treated with betaxolol, brimonidine 0.2%, dorzolamide or timolol were significantly (p < 0.05) more likely to discontinue or change their monotherapeutic regimen than those receiving latanoprost.

Another study, a retrospective medical chart review conducted by Diestelhorst and colleagues in four European countries, looked at persistence of initial monotherapy and its clinical impact among 94 patients with glaucoma or ocular hypertension who received latanoprost and 166 treated with a beta-blocker. Those taking a beta-blocker were 3.8 times more likely to change therapy than those receiving latanoprost. The latanoprost group achieved a greater mean decrease in IOP (7.4 mmHg) vs. the beta-blocker cohort (4.6 mmHg). Fewer patients treated with latanoprost had worsened optic nerve head excavation (1.7%) than those taking a beta-blocker (14.2%).

A third study, a population-based retrospective chort review by Reardon and associates, involved 2,376 patients treated with latanoprost, 993 receiving bimatoprost and 987 taking travoprost. Compared with the latanoprost group, those receiving bimatoprost were 38% more likely to discontinue and 31% more apt to discontinue or change therapy, while those treated with travoprost were 36% more likely to discontinue and 29% more inclined to discontinue or change their regimen.

These findings are significant in that greater persistence with initial monotherapy among glaucoma and ocular hypertension patients is associated with improved outcomes and reduced long-term costs of care.

Study Examines Lumigan's Effect on Aqueous Outflow

Lumigan (bimatoprost) increases aqueous outflow through both pressure-sensitive and pressure-insensitive routes without affecting inflow in those with elevated IOP and glaucoma, according to a study by Brubaker et al. of the drug's safety, efficacy and mechanism of action.

A double-masked, placebo-controlled, randomized, crossover study involving 29 patients with ocular hypertension or glaucoma found that bimatoprost lowered IOP by 32% relative to placebo. The facility of outflow -- drainage via the pressure-sensitive route -- increased by 47%, while the rate of pressure-insensitive outflow also increased.

The study confirmed that bimatoprost's increased outflow mechanism is the same in glaucomatous eyes as it is in normal eyes. Bimatoprost is believed to lower IOP by increasing aqueous outflow through both the trabecular meshwork and uveoscleral routes.

Travatan More Effective In Blacks Than in Whites

Travoprost 0.004% (Travatan) lowered intraocular pressure more in blacks than in nonblacks in two prospective, controlled, multicenter, double-masked studies lasting 6 months (n=594) and 12 months (n=787).

Netland et al. reported that travoprost was more effective than timolol (Timoptic) in both racial groups; this difference was significantly more pronounced among blacks. Travoprost was also superior to latanoprost (Xalatan) in blacks, although the change from baseline was not significant. A significantly greater proportion of blacks achieved an IOP below 16 mm Hg with travoprost than with latanoprost or timolol.

The differences in mean IOP between blacks and nonblacks with travoprost may reflect differences in prostaglandin metabolism or prostaglandin receptors. Little is known about racial or ethnic variations in prostaglandin metabolism; however, Somova et al. showed that renal prostaglandin synthesis differed between black Africans with hypertension and white Africans with hypertension.

It is well-documented that glaucoma, advanced glaucomatous damage and blindness due to glaucoma are more prevalent in blacks than in whites. Not only is race a risk factor for the disease, but race may also influence responses to laser treatment, surgery and medical therapy. The two present studies lend credence to the latter speculation.