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Adjunctive Medications to Lower Intraocular Pressure Go Head-to-Head: Presented at AAO

By Earl R. Nichols

NEW ORLEANS, LA -- November 13, 2007 -- Researchers report that adding brimonidine Purite to a prostaglandin lowers intraocular pressure (IOP) better than either dorzolamide 2% or brinzolamide 1% in patients with glaucoma.

The investigators presented their data in a poster session here on November 11 at the annual meeting of the American Academy of Ophthalmology (AAO).

Almost half of all patients with glaucoma are unable to achieve sufficient IOP with one drug alone and have to use 2 or more adjunctive medications. Even when patients use prostaglandins -- the most effective drugs in treating glaucoma -- approximately 20% need a secondary ocular hypotensive drug. The drug most commonly added to a prostaglandin is the beta-blocker timolol, but this is often contraindicated in older patients who might already be using a beta-blocker for a cardiovascular condition. Other drugs that are used in place of the beta-blocker may include carbonic anhydrase inhibitors (CAIs).

This study, conducted by Thomas Bournias, MD, Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Evanston, Illinois, United States, included 3 groups of patients who were receiving prostaglandins at baseline. The prostaglandins being used were latanoprost (n = 35), bimatoprost (n = 71), and travoprost (n = 14). The patients were also given brimonidine Purite (n = 41), dorzolamide 2% (n = 40), or brinzolamide 1% (n = 39). Patients instilled the adjunctive drugs in only 1 eye 3 times per day, as indicated on the labelling, and were then followed for 4 months.

All baseline demographics were matched between the groups. Baseline IOP among the groups ranged from 20.2 mmHg to 21.9 mmHg.

Overall, 87% of patients receiving brimonidine Purite had a final IOP of less than 18 mmHg compared with 35% of those receiving dorzolamide 2% and 33% of those on brinzolamide 1%.

The maximum efficacy of the combination therapy, or peak effect, was seen within 2 hours of late morning dosing. Most patients using brimonidine Purite experienced additional IOP-lowering of 4.8 mmHg on top of what was achieved with the prostaglandin. This compares with an additional IOP-lowering of 3.4 mmHg for both CAIs.

Trough effect of the drugs (when they were least effective) occurred around late afternoon dosing when patients receiving brimonidine Purite had an additional IOP lowering of 3.9 mmHg compared with 2.7 mmHg for both dorzolamide 2% and brinzolamide 1%. These differences were all statistically significant. What is also important is that the differences occurred as early as one month into the study and carried on for the duration. There were no differences in adverse events between the study groups.

While the absolute differences between the 3 drugs do not seem large, they are important clinically. One major glaucoma study has reported that for every 1 mmHg reduction in IOP, the risk of progression to visual field damage is reduced by 10%. A second study has reported that there was no progressive visual field damage when the patient's IOP could be maintained below 18 mmHg.

This research received no industry funding.


[Presentation title: Comparison of Brimonidine Purite 1.15% Versus Dorzolamide 2% and Brinzolamide 1% as Adjunctive Therapy to Hypotensive Lipids. Abstract Po086]

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