Case Presentation:
The patient is a 58 yo white female with no significant past medical history who presented with severe fatigue and was found to have acute renal failure and hemolytic anemia. Review of symptoms was completely negative with no change in her urinary habits (no dysuria, hematuria, or frequency) or GI habits (no nausea, vomiting, or change in bowel habits). Social and family history were unremarkable. Medications included wellbutrin, synthroid, and prilosec. Physical exam was normal other than scleral icterus. Labs were significant for a creatinine of 3 mg/dl, hematocrit of 27.9, undetectable haptoglobin, elevated LDH, orange urine with bland sediment, and helmet cells on blood smear. Renal ultrasound was normal. Upon further questioning, she reported taking pyridium 100mg tid for five months for “vaginal pain”. It was discontinued and her creatinine and hematocrit returned to normal within a month without further intervention.
Discussion:
Phenazopyridine is available over the counter in several products. It's mechanism of action is unknown, but appears to exert a local anesthetic action on urinary tract mucosa. It's reported adverse reactions include acute renal failure, hemolytic anemia, hepatitis, and methemoglobinemia.
There have been a variety of case reports outlining the spectrum of disease associated with phenazopyridine ingestion. The first paper from 1964 outlined a case of severe hemolytic anemia, and the spectrum of methemoglobinemia, hemolytic anemia and acute renal failure has been reported after an acute ingestion, after a chronic overdose, and after chronically appropriate doses. The mechanism of these adverse reactions is not well understood, but the renal failure has been postulated to result from triaminopyridine, a metabolite that causes vacuolization and necrosis of renal distal tubules.
Although this drug is widely used, only half of consumers know that phenazopyridine is a urinary tract analgesic and even fewer know the potential adverse reactions associated with its use. The lesson to be learned by hospitalists is the importance of a thorough review of all over‐the‐counter (OTC) medications when patients are admitted to the hospital.
Conclusion:
The use of OTC medications is extremely common, and is reported by two‐thirds of all hospitalized patients. Unfortunately, documentation of OTC medications is present on admission in less than 10% of cases. Given that drug related hospitalizations account for 5‐8% of all hospital stays, it is essential that OTC medication use be routinely collected from all patients at the time of hospital admission. As evidenced in this case report, a thorough OTC medication history can avert potentially extensive, and expensive, diagnostic work ups.
Author Disclosure Block:
D.B. Scheurer, None.