Niridazole-induced red/brown urine pigment is associated with increased urinary beta-glucuronidase excretion and a bladder site of formation.

Niridazole caused red/brown urine pigment in a man during treatment for Schistosoma mansoni infection. The urine pigment has been observed during niridazole treatment of schistosomiasis, but has not been documented during treatment of other diseases. Urinary beta-glucuronidase (EC 3.2.1.31) concentration increased proportionately to the amount of red/brown pigment in the urine. Concurrently, sterile pyuria developed. The duration of the time urine was in the bladder was directly related to the concentration of beta-glucuronidase and to the intensity of the red/brown urine color, there being much more in infrequently than in frequently voided urine specimens. Pigment development appears to occur in the bladder. The associated and possibly contributing components appear to be niridazole or one of its metabolites, beta-glucuronidase from the kidneys or from urinary granulocytes, and possibly a schistosomal factor. Given time, this combination generated the red/brown pigment.