Effect of continuous intravenous infusion of carteolol chloride on tissue blood flow in rabbit optic nerve head.

PURPOSE To investigate the effect of an intravenous infusion of carteolol on tissue blood flow in the optic nerve head (ONH) of rabbits. METHODS Rabbits received either a 3-week topical instillation, or a single intravenous injection (10, 20, 30 microg/kg) or a continuous intravenous injection (2.5, 5, 20, 40, 80 microg/kg per hour) of carteolol. The plasma carteolol level was determined by the gas chromatography negative-ion chemical ionization mass spectrometric method. The ONH blood flow was determined by the hydrogen clearance method. RESULTS The plasma level of carteolol after a 3-week instillation was 5.55 ng/mL, and a continuous intravenous injection (5 microg/kg per hour) led to approximately the same plasma level. The continuous intravenous infusion of 5 microg/kg per hour of carteolol significantly increased the ONH blood flow compared to the controls from 30 minutes to 2 hours after the beginning of the infusion (n = 10). The mean blood pressure and intraocular pressure (n = 6) were not significantly changed during the continuous intravenous infusion of carteolol. CONCLUSIONS These results suggest that the plasma carteolol level in rabbits after long-term instillation can increase the ONH blood flow. We conclude that the increase resulted from a reduction in the vascular resistance in the ONH.