Acute Renal Failure and Pigmentation Due to Phenazopyridine (Pyridium®)

Abstract

Two patients developed evidence of acute renal failure after receiving larger than recommended doses of phenazopyridine (Pyridium®) for urinary tract analgesia. Both patients had evidence of preexisting renal disease. The patients developed skin pigmentation, pigmentation of the urine, and highly pigmented casts and crystals in the urine sediment. Both had transient oliguria and impaired renal function. One patient died suddenly from pulmonary embolus: Postmortem examination showed pigmented tubular casts and degenerative and regenerative changes in the epithelial cells of the collecting ducts. The localization of the lesions was similar to that reported in studies of phenazopyridine toxicity. Phenazopyridine should be used with caution and in reduced doses in patients with evidence of renal impairment.