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Timolol-Dorzolamide Lowers Intraocular Pressure in Glaucoma Patients the Same as Timolol-Latanoprost: Presented at ARVO

By Earl R. Nichols

FT. LAUDERDALE, FL -- May 6, 2004 -- There does not appear to be any difference in reduction of intraocular pressure (IOP) between the two combination therapies of fixed-dose timolol/dorzolamide (Cosopt) and concomitant timolol and latanoprost.

According to a poster presented here at the Association for Research in Vision and Ophthalmology Annual Meeting, both therapies reduce IOP by an average of 1.3 mm Hg over timolol alone.

Grace Lee, MD, glaucoma fellow, Wills Eye Hospital, Philadelphia, Pennsylvania, United States, presented the results of a small study involving 29 patients with open angle glaucoma, pseudoexfoliative glaucoma or normal tension glaucoma.

Patients underwent a 4-week washout period in which they were treated with timolol alone, and were then randomised to 4 weeks with either the fixed-dose combination of timolol/dorzolamide or the individual products timolol and latanoprost administered concomitantly.

After the treatment period, patients went through a second 4-week washout period using timolol alone and were then switched to the other treatment arm. The endpoint was difference in IOP reduction when the patients were switched from timolol alone to one of the study regimens.

No statistically significant difference in IOP reduction was seen between the two regimens after either study period. In both 4-week periods, IOP was lowered by a mean of 1.3 mm Hg over what it had already been lowered during the timolol-only washout phase.

"These results are important given the plethora of fixed combinations that are available," Dr. Grace said. "Given that glaucoma patients are often on multiple medications, the use of fixed dose combinations may offer a simplification of the regimen and improve patient compliance."

Other studies have reported mixed results with these regimens. One study showed timolol-latanoprost to lower IOP more than the fixed dose of timolol-dorzolamide (Ophthalmology. 2004 Feb;111(2):276-82), but at least one study has reported that there was no meaningful difference in IOP-lowering between the two agents (Eye. 2004 Dec;18(12):1264-9).

It is questionable whether a physician would switch a patient from one regimen to the other when the change in IOP is only 1.3 mm Hg, Dr. Grace said.

The study was funded by Merck & Co, maker of the fixed dose combination of timolol-dorzomamide (Cosopt).


[Presentation title: Comparison of Intraocular Pressure Lowering Efficacy of Fixed Combination Timolol-Dorzolamide versus Timolol Plus Latanoprost. Poster 3797/B155]

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