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The fixed combination of brimonidine tartrate 0.2% and timolol maleate 0.5% (Combigan, Allergan) is an effective and well-tolerated substitute treatment for patients whose IOP remains uncontrolled under prostaglandin analog monotherapy or any other fixed combination of hypotensive agents, according to a poster presentation made at the World Ophthalmology Congress.
"We did this study to understand better how this new combined therapy would affect our Mexican patients," said the study's lead author, Curt Hartleben, MD, a glaucoma specialist at the Instituto de Oftalmolog쟠Conde de Valenciana in Mexico City. "We had previously done research individually with prostaglandin analogs, finding that our Mexican population had very good response to them. Also, we all had previous good experience with other combined drugs for treatment of glaucoma, especially the fixed combination of timolol and dorzolamide," he said. Dr. Hartleben is a member of the Mexican Glaucoma Research Group, a nonprofit and unaffiliated group of glaucoma specialists who are both clinicians and researchers in 10 different centers throughout Mexico; the group is interested in conducting multicentric clinical research in glaucoma.
They measured IOP at trough (8 a.m.) and at peak (10 a.m.). Subjects' measurements were taken at baseline and monthly for 6 months.
"Originally, we had thought of a short study, but our findings at 3 months suggested that our pressure-lowering curve was still dropping, so we extended our original study to 6 months," Dr. Hartleben said.
After informed consent, subjects were given a complete ophthalmic checkup, including visual field tests and dilated fundus examinations. Safety was evaluated at slit lamp for adverse effects as well as interrogation for systemic side effects. At the end of the study, both patients and physicians were asked to fill a satisfaction questionnaire.
"After our study ended, a good number of patients remained available and kept using the fixed combination of brimonidine and timolol. We followed 75 patients to assess allergy incidence. These patients were seen for a minimum of 12 and a maximum of 18 months," he said.
The researchers studied 301 patients (601 eyes) whose initial IOP under previous treatment was an average 18.49 mm Hg at 10 a.m. At 3 months, IOP had decreased 14% to 78%. The study population had a mean age of 62.4 years. Seventy-two percent were female, a sex distribution that Dr. Hartleben said is similar to that at the researchers' practices in Mexico. Eighty-six percent of patients studied had POAG, and 71.2% had been taking prostaglandin analogs. The patients' visual fields were only mildly disturbed, mean MD –4.54 ± 4.93 dB, and median visual acuity was 20/30.
The second phase of the study (the 6-month extension) included 150 patients (300 eyes); at 6 months, researchers reported that mean IOP decreased –4.24 mm Hg, or 22.95% at peak, 10 a.m.
"When we studied how many patients were below a given level of IOP, we found that overall, only 3.67% of patients had less than 15 mm Hg on previous treatment, and at 6 months, this group was 46%," Dr. Hartleben said.
Side effects were minimal at 6 months, he said, with 11 subjects reporting symptoms such as blurred vision, photophobia, and conjunctivitis. Four of those subjects abandoned treatment but not because of systemic side effects.