[Effects of topically applied bunazosin hydrochloride on choroidal capillary blood flow and intraocular pressure of rabbit eye].

The effects of topically applied bunazosin hydrochloride, a selective alpha 1 blocker under development as a drug to treat glaucoma, were studied in regard to the choroidal capillary blood flow, intraocular pressure (IOP), and blood pressure in albino rabbit eyes in comparison with propranolol hydrochloride, a non-selective beta blocker. The capillary blood flow was measured using a thermal diffusion flowmeter. Single instillations (50 ul) of 0.005% bunazosin hydrochloride, lowered the IOP to almost the same degree as did 1.0% propranolol hydrochloride. The maximum decreases from initial IOP were 3.3 +/- 1.2, 3.6 +/- 1.7 mmHg for bunazosin hydrochloride and propranolol hydrochloride, respectively. No significant effect on mean blood pressure was observed with these instillations. The choroidal capillary blood flow was reduced by propranolol hydrochloride for 3 hours after instillation (maximum rate of decrease was 10.0 +/- 4.6%), while it was increased by bunazosin hydrochloride for 150 min. (maximum rate of increase was 8.3 +/- 3.8%). When phenylephrine hydrochloride (0.5%), an alpha 1 agonist, was instilled with bunazosin hydrochloride (0.005%), the choroidal capillary blood flow showed no significant change. This was felt to imply an action mechanism involving the alpha 1 receptor.