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Results of a prospective, randomized, investigator-masked trial comparing brimonidine 0.15% with oxidative preservative (Purite) (Alphagan P, Allergan) and dorzolamide 2% (Trusopt, Merck) as adjuncts to latanoprost 0.005% (Xalatan, Pfizer) show the addition of either agent results in further IOP reduction, but the IOP-lowering effect was greater in the brimonidine/oxidative preservative group.
"A prostaglandin analog is considered first-line medical therapy for IOP-lowering, and latanoprost is the most commonly prescribed agent in that class," he said. "However, when considering dual therapy for a patient who[se condition] does not have adequate response to monotherapy, the results of this study support trying brimonidine [with oxidative preservative] first before reaching for dorzolamide. Of course, if sufficient IOP-lowering is still not achieved, then physicians should consider switching to a topical carbonic anhydrase inhibitor before adding a third agent," said Dr. Mundorf, who is a private solo practitioner specializing in glaucoma in Charlotte, NC.
The multicenter study enrolled patients with open-angle glaucoma (n = 49) or ocular hypertension (n = 6) who had a bilateral IOP of 16 mm Hg or greater after a minimum of 6 weeks of latanoprost monotherapy. The patients continued using the latanoprost at 8 p.m. and were randomly assigned to begin twice-daily treatment with brimonidine/oxidative preservative (n = 27) or dorzolamide (n = 28) at 8 a.m. and 8:15 p.m. The investigators were blind as to which adjunctive medicine the patients were randomly assigned. Patients with a history of using either of the adjunctive therapies were excluded from the study.
At both 1 and 3 months, IOP measured at peak effect was lower in the brimonidine/preservative-treated patients compared with the dorzolamide group. The difference between groups was statistically significant at 1 month. Mean IOP at 1 month was 15.1 mm Hg in patients treated with brimonidine/preservative and 16.7 mm Hg in the dorzolamide group. Mean peak IOP values at 3 months in the brimonidine/preservative and dorzolamide groups were 15.6 and 16.5 mm Hg, respectively. The mean IOP reduction from baseline at 1 month also was significantly greater in the brimonidine/preservative group than in patients treated with dorzolamide (–5.7 versus –4.0 mm Hg.)
No significant differences in mean IOP at trough or mean trough IOP reduction existed between groups at either follow-up visit. Mean trough effect IOP at 3 months was 18.7 mm Hg in the dorzolamide group and 18.5 mm Hg in patients treated with brimonidine/oxidative preservative.
"Both dorzolamide and brimonidine [with oxidative preservative] are approved for t.i.d. administration, but they are indicated for b.i.d. dosing outside the United States and often [are] prescribed twice daily in this country. Regardless of what administration schedule they use, physicians who are concerned about a trough effect should check the patient at a trough time," Dr. Mundorf said.
Treatment was considered clinically successful if the investigator determined that the patient should continue the existing regimen. A higher proportion of patients in the brimonidine/preservative group compared with the dorzolamide group were considered to have clinically successful outcomes (84.6% versus 66.7%), although the difference was not statistically significant.