Effects of frusemide on the urinary excretion of dopamine and 5‐hydroxytryptamine in normal man

The effects of frusemide on the urinary excretion of dopamine and 5hydroxytryptamine (5‐HT) were investigated in eight healthy male subjects in a randomized, placebo‐controlled, cross‐over study. Frusemide produced the expected rise in urinary dopamine excretion but it did not affect 5‐HT excretion when compared with placebo. The lack of an effect on 5‐HT excretion in man contrasts with studies in the rat which have reported a marked increase in 5‐HT excretion after administration of this loop diuretic.