The influence of topically applied bethanidine on intraocular pressure and pupil in the rabbit.

Bethanidine sulphate was administered topically to the eyes of conscious rabbits using a 0.5%, 1%, 2% and 5% solution of the drug. The intraocular pressures and pupil sizes were measured in the right treated and left control eyes at 0,1,2,3, 6 and 24 hrs. With all concentrations a pressure decrease with a maximum between 3 and 6 hrs after topical treatment occured. The 5% solution of bethanidine sulphate showed a delayed effect which was submaximal when compared to the 2% bethanidine solution. Using the 1% and 2% solution a ppressure decrease probably due to systemic action of the drug happened in the untreated control eyes. In all experiments the pressure responses had disappeared after 24 hrs in the treated and untreated eyes respectively. By means of the experimental conditions in this study no significant pupillary reactions were found after bethanidine application. The tension effect of 0.5% adrenaline borate remained essentially unchanged when repeated with additional 1% topical bethanidine. Some aspects of sympatholytic drug action on the intraocular pressure in the rabbit are discussed.