Effect of norepinephrine on the urinary excretion of purine bases and oxypurinol

To examine whether norepinephrine affects the plasma concentrations and urinary excretion of purine bases and oxypurinol, we orally administered allopurinol (300 mg) to 5 healthy subjects and 9 hours later intravenously administered norepinephrine (12 to 20 mug/kg body weight), which causes a more than 10 mm Hg increase in diastolic pressure for 2 hours. Norepinephrine decreased the urinary excretion of uric acid by 33% (P < .01), oxypurinol by 32% (P < .01), and xanthine by 51% (P < .01), as well as the fractional clearance of uric acid by 32% (P < .01), oxypurinol by 24% (P < .05), and xanthine by 21% (P < .05) when measured 1 to 2 hours after administration. These results indicate that norepinephrine decreases the urinary excretion of uric cid, oxypurinol, and xanthine, probably via hemodynamic change. It is also suggested that the hypouricemic effect of allopurinol may be more potent than that expected in gout patients with enhanced sympathetic tone, such as in salt-sensitive hypertension. Copyright (C) 2001 by WB. Saunders Company.