An 87-year-old man was referred to the hospital for dysuria. His medical history consisted of mild dementia and recurrent urinary tract infections. On examination, vital signs were normal and the patient did not seem to be in distress. His sclera were mildly icteric, and central cyanosis was observed. Deep lemon-yellow discoloration of all nails was also noted. Other than an enlarged prostate, findings on physical examination were unremarkable. Laboratory tests revealed macrocytic anemia (hemoglobin level, 11.9 g/dL; mean corpuscular volume, 99 fL), a bilirubin level of 104 µmol/L (mostly unconjugated), a lactate dehydrogenase level of 1063 U, a haptoglobin level of 11 mg/dL, and a creatinine level of 275 µmol/L. At room air, arterial PO₂ was 92 mm Hg. These findings led to the suspicion of methemoglobinemia, which was confirmed by a methemoglobin level of 12.2%. The urine was orange and contained pus. On further questioning, the patient's son discovered that his father had been taking phenazopyridine, 300 mg/d, for more than 3 years. Therapy with the drug was discontinued, and the bilirubin level decreased. The patient left the hospital against medical advice 24 hours after admission. Further testing and follow-up were not possible.

Phenazopyridine was recently reported as a cause of chronic intravascular hemolysis when taken at high doses [1, 2]. This drug also causes acute methemoglobinemia after intentional overdoses [3, 4] and causes altered skin pigmentation [5], both in association with renal failure. To our knowledge, yellow discoloration of the nails induced by phenazopyridine has not been reported. As in previous reports of phenazopyridine and altered skin pigmentation, the striking nail color contrasted with the mild scleral icterus and could not be explained by the mild hyperbilirubinemia. Long-term use and the toxic manifestations of this commonly prescribed drug are increasingly being recognized. The presence of intravascular hemolysis, methemoglobinemia, and abnormal pigmentation, alone or in combination, should raise the suspicion of phenazopyridine toxicity. In patients with renal failure, these side effects may be as pronounced at lower doses.