REPLY
Chronic Severe Hemolytic Anemia from Phenazopyridine
Anand B. Karnad and
Robert J. Thomas
15 January 1995 | Volume 122 Issue 2 | Pages 156-157
IN RESPONSE:
We stand corrected. Pyridium itself is not available over the counter. However, the pharmacist who notified us of our patient's drug habit confirmed that our patient did purchase more than 12 boxes per week of one of several preparations available over the counter (Azostandard, Polymedica Pharmaceutical Inc., Woburn, Massachusetts; Reazo, Reese Chemical, Cleveland, Ohio; and Baridium, Pfeiffer Co., Wilkes-Barre, Pennsylvania) that contain 95 to 100 mg of phenazopyridine hydrochloride per tablet [1, 2].
We had overlooked the classic paper by Gabor and colleagues[3] that was perhaps the first to thoroughly document hemolysis caused by phenazopyridine. Other reports[4] also describe Heinz-body hemolytic anemia as an acute or subacute phenomenon in the setting of renal failure. We believe that our patient, who had normal renal function, represents the first clearly documented case of severe chronic hemolytic anemia caused by the abuse of phenazopyridine in over-the-counter preparations. Finally, we agree with Dr. Gabor that it is important to highlight this unique toxic reaction of phenazopyridine because it is a commonly prescribed drug (Pyridium) in patients with various urinary tract symptoms. Its availability in over-the-counter preparations underscores the importance of recognizing signs of phenazopyridine toxicity—the syndrome of lemon-yellow skin color in the absence of jaundice, of hemolysis, and of bite cells on the blood smear. We salute the astute pharmacist who brought this to our attention.
1. Physicians Desk Reference for Non-Prescription Drugs. 15th ed. New Jersey: Medical Economics; 1994:630, 647.
2. Drug: Facts and Comparisons (Updates: Baridium). St. Louis: Wolter Kluwer; 1994.
3. Gabor EP, Lowenstein L, De Leeuw NK. Hemolytic anemia induced by Phenylazo-Diamino-Pyridine (Pyridium). Can Med Assoc J. 1964; 91:756-9.
4. Fincher ME, Campbell HT. Methemoglobinemia and hemolytic anemia after phenazopyridine hydrochloride (Pyridium) administration in end-stage renal disease. South Med J. 1989; 82:372-4.
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