Exceeding the recommended dose in patients with good renal function or administering the usual dose to patients with impaired renal function (common in elderly patients), may lead to increased serum levels and toxic reactions. Methemoglobinemia generally follows a massive, acute overdose. Methylene blue, 1 to 2 mg/kg body weight intravenously, should cause prompt reduction of the methemoglobinemia and disappearance of the cyanosis which is an aid in diagnosis. Oxidative Heinz body hemolytic anemia may also occur, and "bite cells" (degmacytes) may be present in a chronic overdosage situation. Red blood cell G-6-PD deficiency may predispose to hemolysis. Renal and hepatic impairment and occasional failure, usually due to hypersensitivity, may also occur.
Phenazopyridine Hydrochloride should not be used in patients who have previously exhibited hypersensitivity to it. The use of Phenazopyridine Hydrochloride is contraindicated in patients with renal insufficiency.
Last reviewed on RxList: 8/22/2007
This monograph has been modified to include the generic and brand name in many instances.
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