Q: What is the mechanism of action for non-selective beta-blockers to reduce portal hypertension?
Answer: Beta-blockers do not work directly to reduce portal hypertension. It's the 'down the stream' effect which decreases portal hypertension by decreasing portal venous inflow. The two recommended nonselective beta-blockers are propranolol and nadolol. Nonselective beta-blockers block the adrenergic dilatory tone in mesenteric arterioles. This causes an unopposed alpha-adrenergic mediated vasoconstriction. This vasoconstriction causes decrease portal venous inflow.
This is one of the major reasons that cardioselective beta-blockers such as atenolol doesn't have a good effect on portal hypertension, as it tends to works directly via decreasing cardiac output.
#hepatology
References:
1. Sanyal AJ, Shiffman ML. The pharmacologic treatment of portal hypertension. Annu Rev Gastrointest Pharmacol 1996; :242.
2. Hillon P, Lebrec D, Muńoz C, Jungers M, Goldfarb G, Benhamou JP. Comparison of the effects of a cardioselective and a nonselective beta-blocker on portal hypertension in patients with cirrhosis. Hepatology. 1982 Sep-Oct;2(5):528-31. doi: 10.1002/hep.1840020503. PMID: 7118065.
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