NIPRADILOL, A NEW BETA-BLOCKER WITH VASODILATORY PROPERTIES, IN EXPERIMENTAL PORTAL-HYPERTENSION - A COMPARATIVE HEMODYNAMIC-STUDY WITH PROPRANOLOL

The haemodynamic effects of nipradilol, a new non-selective beta-adren oreceptor blocker with vasodilating actions like nitroglycerin, were e xamined in rats with portal hypertension due to portal vein stenosis. Portal hypertensive rats were divided into five groups receiving infus ion of placebo, 3 mg of propranolol, 300, 600 and 1200 mug of nipradil ol. At its highest dose, nipradilol achieved a reduction of 34.4 +/- 4 .4% in heart rate which was similar to that in the propranolol group ( 36.5 +/- 2.4%). Also for other systemic haemodynamic parameters, the n ipradilol 1200 mug group exhibited changes not significantly different from those in the propranolol group; mean arterial pressure (-13 vs - 14%), cardiac index (-37 vs -31%) and systemic vascular resistance (+2 9 vs +32%). In contrast to the similar changes in the systemic circula tion, a 1200 mug dose of nipradilol lowered portal pressure significan tly more than propranolol (-4.3 +/- 0.6 vs -2.9 +/- 0.2 mmHg, P < 0.05 ). Nipradilol then reduced portal blood flow by 22% (P < 0.05) without a significant change in portocollateral resistance. On the other hand , propranolol not only caused a reduction in portal blood flow of 30% (P < 0.01), but also an increase in portocollateral resistance of 21% (P < 0.05). The results suggest that nipradilol may ensure a more effe ctive control of portal hypertension than propranolol, presumably via its venodilatory action on portocollateral vessels.