The Cardiovascular, Pulmonary, and Ocular Hypotensive Effects of 0.2% Brimonidine

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Abstract
Objective: To compare the cardiovascular, pulmonary, and ocular hypotensive effects of 0.2% brimonidine tartrate with those of 0.5% timolol maleate, 0.25% betaxolol suspension, and brimonidine vehicle. Design and Patients: A single-center, double-masked, randomized, crossover study of 24 young, healthy men. Interventions: Baseline heart rate, blood pressure, respiratory rate, and intraocular pressure were recorded at hour 0. At hour 2, heart rate, blood pressure, respiratory rate, and forced expiratory volume in 1 second were measured and a 15-minute treadmill test performed. Hour 0 measurements were repeated at hour 4. On four subsequent visits, we instilled one drop of a study medication into each eye after the baseline measurements at hour 0. Results: Timolol reduced resting (−5.3 to −6.5 beats/min;P≤.004) and exercise-induced heart rate (−4.3 to −13.6 beats/min;P≤.022) compared with brimonidine, betaxolol suspension, and brimonidine vehicle. At hour 4, brimonidine reduced resting systolic blood pressure compared with all other study medications (−5.2 to −7.3 mm Hg;P≤.024). Timolol reduced systolic blood pressure during exercise and brimonidine reduced systolic blood pressure during recovery more than betaxolol suspension and brimonidine vehicle (−5.1 to −7.7 mm Hg;P≤.033; and −5.4 to −6.0 mm Hg;P≤.002, respectively). Mean respiratory rate and forced expiratory volume in 1 second were not significantly altered by any study medication. At hour 4, brimonidine lowered intraocular pressure as well as timolol and better than betaxolol suspension (−1.9 mm Hg;P<.001) or brimonidine vehicle (−1.8 mm Hg;P<.001). Conclusions: The cardiopulmonary effects of 0.2% brimonidine were limited to a slight reduction in systolic blood pressure during recovery from exercise and at 4 hours after instillation. The ocular hypotensive effect of brimonidine was comparable to that of timolol and greater than that of betaxolol suspension in this patient population.