Additive effect of betaxolol and epinephrine in primary open angle glaucoma

R. C. Allen and D. L. Epstein

Betaxolol hydrochloride is a topical beta 1-blocking agent that has been found to be safe and effective in lowering intraocular pressure (IOP) in patients with glaucoma. We administered open-label epinephrine for four weeks to 19 patients who were already being treated with masked 0.5% timolol maleate or 0.5% betaxolol. In patients receiving betaxolol, epinephrine produced a significant additional lowering of mean IOP from 24.5 +/- 0.7 to 19.4 +/- 0.6 mm Hg at one week (P less than .0001) and to 20.7 +/- 0.5 mm Hg at four weeks (P less than .0001). This was accompanied by a statistically significant increase in mean outflow facility from 0.12 +/- 0.1 to 0.17 +/- 0.03 microL/min/mm Hg at one week (P less than or equal to .05) and to 0.18 +/- 0.02 microliter/min/mm Hg at four weeks (P less than or equal to .004). Consistent with previous reports, patients receiving timolol exhibited no significant changes in IOP or outflow facility after the addition of epinephrine to their treatment regimen. These results suggest that epinephrine's agonist effect on the outflow channels is mediated through beta 2-adrenergic receptors and that combined therapy with betaxolol and epinephrine may be clinically useful.