Effect of ophthalmic metipranolol and timolol on exerise-induced tachycardia
1Research and Development Department, Bausch & Lomb Pharmaceutical Division *Tampa Cardiovascular Associates, Tampa, Florida, U.S.A.
Purpose:
We compared the systemic beta-adrenoceptor blockade elicited by metipranolol with timolol in a randomized, double-masked, multiple crossover study in 24 healthy volunteers.
Methods:
On each of 4 test days, subjects exercised on a treadmill for 10 min at 4 mi/h at a 5% gradient. After a 30-min rest, they received one drop OU of either 0.1 or 0.3% metipranolol HCI, 0.5% timolol maleate, or an artificial tear vehicle.
Results:
With 10 min of exercise, mean heart rate increased from +/-80 to 140 beats/min preinstillation. During the postinstillation exercise, mean heart rate increased to a maximum of 141.5 +/- 19.6, 141.8 +/- 17.2, 139.7 +/- 19.7, and 131.5 +/- 16.9 beats/min in the vehicle, 0.1% metipranolol, 0.3% metipranolol, and 0.5% timolol groups, respectively. Pairwise comparisons at this time revealed a significant difference between timolol and each of the other treatments.
Conclusions:
Given the ocular hypotensive equivalency of various concentrations of metipranolol to timolol in other studies, it appears that metipranolol may have an improved therapeutic index relative to timolol.
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