Nipradilol, a new beta-blocker with vasodilatory properties, in experimental portal hypertension: a comparative haemodynamic study with propranolol.

The haemodynamic effects of nipradilol, a new non-selective beta-adrenoreceptor blocker with vasodilating actions like nitroglycerin, were examined in rats with portal hypertension due to portal vein stenosis. Portal hypertensive rats were divided into five groups receiving infusion of placebo, 3 mg of propranolol, 300, 600 and 1200 micrograms of nipradilol. 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 nipradilol 1200 micrograms 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 (+29 vs +32%). In contrast to the similar changes in the systemic circulation, a 1200 micrograms dose of nipradilol lowered portal pressure significantly 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 effective control of portal hypertension than propranolol, presumably via its venodilatory action on portocollateral vessels.