In case of an overdose of this product, patients should contact a physician, poison control center, or emergency room.
Acute: The amount of a single dose of trimethoprim/sulfamethoxazole that is either associated with symptoms of overdosage or is likely to be life-threatening has not been reported. Signs and symptoms of overdosage reported with sulfonamides include anorexia, colic, nausea, vomiting, dizziness, headache, drowsiness, and unconsciousness. Pyrexia, hematuria, and crystalluria may be noted. Blood dyscrasias and jaundice are potential late manifestations of overdosage. Signs of acute overdosage with trimethoprim include nausea, vomiting, dizziness, headache, mental depression, confusion, and bone marrow depression.
General principles of treatment include the institution of gastric lavage or emesis, forcing oral fluids, and the administration of intravenous fluids if urine output is low and renal function is normal. Acidification of the urine will increase renal elimination of trimethoprim.
The patient should be monitored with blood counts and appropriate blood chemistries, including electrolytes. If a significant blood dyscrasia or jaundice occurs, specific therapy should be instituted for these complications. Peritoneal dialysis is not effective and hemodialysis is only moderately effective in eliminating trimethoprim and sulfamethoxazole.
Chronic: Use of trimethoprim/sulfamethoxazole at high doses and/or for extended periods of time may cause bone marrow depression manifested as thrombocytopenia, leukopenia, and/or megaloblastic anemia. If signs of bone marrow depression occur, the patient should be given leucovorin; 5 to 15 mg leucovorin daily has been recommended by some investigators.
Phenazopyridine Hydrochloride: 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 concentrations and toxic reactions. Methemoglobinemia generally follows a massive, acute overdose. Methylene blue 1 to 2 mg/kg body weight intravenously or ascorbic acid 100 to 200 mg give orally 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.
This therapy is contraindicated for use in patients with a known hypersensitivity to phenazopyridine hydrochloride, trimethoprim or sulfonamides and in those with renal insufficiency or documented megaloblastic anemia due to folate deficiency. Trimethoprim/sulfamethoxazole is also contraindicated in pregnant patients at term and in nursing mothers, because sulfonamides pass the placenta and are excreted in the milk and may cause kernicterus. Trimethoprim/sulfamethoxazole is contraindicated in pediatric patients less than two months of age.
Last reviewed on RxList: 1/28/2005
This monograph has been modified to include the generic and brand name in many instances.
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