The effects of long-term oral clonidine treatment on hepatic and systemic hemodynamics and on quantitative liver function tests were investigated in 15 patients with alcoholic cirrhosis. Clonidine was administered at a mean dose of 0.33 +/- 0.1 mg/day (mean +/- SD) for a mean period of 64 +/- 10 days. Oral clonidine induced a significant reduction in the hepatic venous pressure gradient from 18.8 +/- 3.0 mm Hg to 15.9 +/- 3.4 mm Hg (P less than 0.001), which was the result of an increase in the free hepatic venous pressure from 5.1 +/- 4.2 mm Hg to 8.7 +/- 3.8 mm Hg (P less than 0.05). In 10 of the 15 patients (67%), the reduction in the hepatic venous pressure gradient was greater than 10% of baseline values. Hepatic blood flow did not change significantly after clonidine treatment. Additionally, treatment with clonidine decreased mean arterial pressure by 15.5% +/- 6% (P less than 0.001), heart rate by 17.7% +/- 7% (P less than 0.001), and cardiac output by 14.6% +/- 7% (P less than 0.001). However, systemic vascular resistance did not change significantly. There were no adverse effects on liver function, as shown by the nonsignificant changes in galactose-elimination capacity (149 +/- 59 vs. 170 +/- 58 mg/min), hepatic clearance of indocyanine green (0.19 +/- 0.10 vs. 0.17 +/- 0.07 L/min), and hepatic intrinsic clearance of indocyanine green (0.23 +/- 0.14 vs. 0.21 +/- 0.1 L/min) before and after clonidine treatment, respectively. In none of the patients was the drug withdrawn because of side effects, although 12 subjects complained of dry mouths. This study suggests that in patients with alcoholic cirrhosis, long-term oral clonidine administration achieves a reduction in the hepatic venous pressure gradient without adverse effects on hepatic blood flow and liver function.