Chronic Severe Hemolytic Anemia from Phenazopyridine

Anand B. Karnad; Robert J. Thomas

doi:10.7326/0003-4819-122-2-199501150-00025

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.

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Letters |15 January 1995

Chronic Severe Hemolytic Anemia from Phenazopyridine

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Letters |15 January 1995

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