Bimatoprost IOP advantages and side effects examined

Study provides evidence of IOP reduction when patients are switched to an alternate prostaglandin

Recent research may help glaucoma specialists to move beyond anecdotal evidence to support their decision to move between prostaglandin analogues. The choice can affect not only patient intraocular pressure but also the likelihood that complications will develop.
The largest comparison of IOP-efficacy and side effects of switching between two major prostaglandins found evidence that supports some variation in treatment.
A company-supported study by Jason Bacharach, M.D., Petaluma, Calif., and colleagues found that patients who switched to bimatoprost 0.03% (Lumigan, Allergan, Irvine, Calif.) after six weeks of treatment with latanoprost 0.005% (Xalatan, Pfizer, New York) achieved a “statistically significantly greater” reduction in diurnal IOP than those who remained on latanoprost.
Possible advantages from switching between these medications have been tempered in the past by concerns about the risk of new complications. However, the study authors found an equal chance that patients would develop a moderate or more severe case of conjunctival hyperemia, regardless of whether they remained on latanoprost or were switched to bimatoprost.
“These results support the hypothesis that the tolerability of bimatoprost treatment is improved in patients who use bimatoprost in replacement of latanoprost,” wrote Dr. Bacharach and colleagues, who presented their data in a poster titled “Masked, Randomized, Parallel Comparison of IOP-Lowering Efficacy after Switching to Bimatoprost 0.03% versus Continuing with Latanoprost 0.005%” at the 2009 annual meeting of the American Glaucoma Society in San Diego.
In the 18-week, investigator-masked, multicenter, parallel-group comparison study, 527 glaucoma patients were randomized after six weeks of treatment with latanoprost 0.005% to either continue with that prostaglandin or switch to bimatoprost 0.03%. Their testing included follow-up visits at weeks 12 and 18, which evaluated efficacy using IOP measurements taken at 8 a.m., 12 p.m., and 4 p.m.
The study seemed to provide some support for previous anecdotal reports that patients could obtain a small boost in IOP reduction with the switch.
“I’m not surprised [by the finding] because anecdotally I have heard that before, and this might be evidence to support that assertion,” said Douglas J. Rhee, M.D., assistant professor, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston.
However, the added glaucoma benefits from the switch may be more common than the study’s scope. Dr. Rhee has seen similar IOP-lowering benefits among his patients switched from any one prostaglandin to any other prostaglandin, in individual circumstances.
The “promising” study findings would have more impact if the study also compared the efficacy of moving patients from bimatoprost to latanoprost, Dr. Rhee said.
“If patients are going to have an improvement—and most of them will not—it is equally possible to happen in moving from any one to the other, which makes one very suspicious of compliance being a factor,” Dr. Rhee said.
The other leading finding that complications were no more common in patients switched to bimatoprost than in those who remained on latanoprost also drew some reservations. Edmund P. Farris, M.D., clinical associate professor, Department of Ophthalmology, New York University Medical Center, New York, noted that “a significant number” of patients switched to bimatoprost would have an increased chance of developing hyperemia than if they were left on latanoprost.
Although Dr. Farris found the large study praiseworthy, it tended to support his experience that many such medications are efficacious with “subtle differences.”
Previous research he conducted and presented at the World Glaucoma Conference similarly found small hyperemia rate differences among patients switched between latanoprost and travoprost, for example. “All of these medications work,” he said.
The biggest limitation on the study’s clinical applicability may be the use of a six-week induction period of latanoprost that is likely far less than most clinicians would prescribe before considering a switch.
The study design also may not reflect the extent of hyperemia present in bimatoprost patients. The authors depended on scale grading of hyperemia and reported change of at least two grades that left small increases unreported.
Any occurrence of hyperemia is a “very real concern” to patients, Dr. Rhee said, even though clinicians are more concerned about IOP impacts. For patients, it is important to reduce hyperemia, which can make them appear tired or that they have been drinking.
“They get concerned that something is obviously wrong with their eye,” he said.
Dr. Rhee echoed the call for a more aggressive comparison of alternative sequences of various prostaglandins to identify strengths among the current prescribing patterns used by ophthalmologists as they continue to try to balance efficacy and side effects.

Editors’ note: Dr. Rhee has financial interests with Alcon (Fort Worth, Texas), Allergan (Irvine, Calif.), and Pfizer (New York). Dr. Farris has financial interests with Alcon and Allergan.

Contact information

Farris: 914-725-5556, edfarris@optonline.net
Rhee: 617-573-3670, dougrhee@aol.com