To examine whether furosemide affects the plasma concentration and urinary
excretion of purine bases and oxypurinol, we administered allopurinol (300
mg) orally to 6 healthy subjects and then administered furosemide (20 mg) i
ntravenously 10 hours later. Furosemide (20 mg) decreased the urinary excre
tion of uric acid by 40% (P < .01), oxypurinol by 39% (P < .05), and xanthi
ne by 43% (P < .05) and the fractional clearance of uric acid by 45% (P < .
01) and oxypurinol by 34% (P < .05) when measured 1 to 2 hours after admini
stration. Moreover, furosemide increased the plasma concentration of uric a
cid by 6% at 1.5 hours after administration. These results indicate that fu
rosemide may decrease the urinary excretion of uric acid and oxypurinol by
acting on their common renal transport pathway(s), In addition, it is sugge
sted that the effect of furosemide on oxypurinol is clinically important, s
ince the hypouricemic effect of allopurinol may become more potent as a res
ult. Copyright (C) 2001 by W.B. Saunders Company.