Systemic effects of three beta-blocker eyedrops: comparison in healthy volunteers of beta 1- and beta 2-adrenoreceptor inhibition.

The beta 1- and beta 2-adrenoreceptor blockade by means of the systemic diffusion of three beta-blocker eyedrops--timolol, carteolol, and betaxolol--was evaluated in a randomized, single-blind, three-way crossover study in 18 volunteers. The blockade was evaluated by analyzing the variations of the beta 1- and beta 2-blockade effects of isoproterenol before and after instillation of one drop in each eye. The beta 1-blockade effect was judged on the variation of heart rate, and the beta 2-blockade effect was judged on the change in peripheral blood flow measured by veno-occlusive plethysmography. Comparison of the blockade by these drops showed that carteolol and timolol totally inhibited the beta 1 and beta 2 effects of a dose of isoproterenol able to increase heart rate by 50% (placebo eyedrops were used as a control). Betaxolol differ significantly because it allowed the same effects with the same dose of isoproterenol. Intensity of the blockade was measured by comparison of the effective doses of isoproterenol. Carteolol and timolol were shown to be four times more inhibitory.

RCT Entities:   Population Interventions Outcomes