Objective: To study the cardiopulmonary safety and ocular hypotensive efficacy of topical betaxolol hydrochloride 0.5% (a selective beta-1 blocker) in patients with unacceptably elevated intraocular pressure (IOP) and respiratory dysfunction.
Methods: Thirty-one patients with poor control of elevated IOP were selected on the basis of coexistent respiratory disease which could be exacerbated by beta-antagonist administration and/or who had past adverse reactions to topical timolol. Using an open-label design, the ophthalmic, cardiovascular and pulmonary parameters of these patients were measured before betaxolol therapy, for four hours immediately after the first administration of the drug, and after one, four and 12 weeks of therapy. The screening and 12-week examinations included a bronchial challenge with methacholine, a non-specific bronchoconstricting agent.
Results: IOP reduction was significant at all time points measured after first instillation of betaxolol, with a mean maximum fall of 8.4 (SD, 3.2) mmHg (95% Cl -9.545 to -7.261) from a baseline mean IOP of 23.9 (SD, 3.8) mmHg. Over 12 weeks of therapy, the mean reduction from baseline in IOP was 3.9 (SD, 2.6) mmHg (95% Cl -4.908 to -2.988). After first instillation of betaxolol, mean arterial pressure (MAP) fell transiently to a mean maximum fall of 3.9 (SD, 9.3) mmHg (95% Cl -7.159 to -0.582), from a mean baseline MAP of 107.7 (SD, 9.4) mmHg. Heart rate did not change. There were no changes in any of the respiratory parameters measured: forced expiratory volume in one second, forced vital capacity and peak expiratory flow rate. Over 12 weeks of betaxolol therapy, there were no changes in any of the above systemic parameters and no change in mean bronchial reactivity as measured by methacholine challenge. Of the 31 patients, who included 13 patients with previous intolerance to timolol (a non-selective beta-antagonist), only one showed intolerance to betaxolol.
Conclusions: Betaxolol appears to be an effective and well tolerated ocular hypotensive agent in a typical glaucoma population, which includes many patients with cardiopulmonary disease. Individual intolerance to betaxolol will continue to occur and care is always required when patients with cardiac or respiratory dysfunction are exposed to any beta-antagonist.