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Post-marketing experience in Europe over 10 years (August 1984 through December 1994) in an estimated 10 million patients provided reports of 66 instances of overdose (maximum dose per body mass of 54 mg/kg, maximum total dose of 1800 mg), including eight children 6 years of age or under. Three deaths have occurred in association with dexfenfluramine overdosage. One patient with a history of suicide attempts ingested 1800 mg dexfenfluramine and 20 to 30 capsules of Tranxene (clorazepate), one patient was found dead, assumed to have consumed approximately 1500 mg of dexfenfluramine, and the third patient consumed dexfenfluramine (quantity unknown) and several other drugs in an apparent suicide. The second patient had post-mortem levels of dexfenfluramine of 3300 ng/mL, and positive levels for amphetamines and cannabinoids. The exact causes of death were unknown. In 23 other cases of dexfenfluramine overdose, plasma drug levels were determined; the maximum reported plasma drug level for dexfenfluramine was 778 ng/mL (with d-norfenfluramine 37 ng/mL); the maximum d-norfenfluramine level was 371 ng/mL (with dexfenfluramine 483 ng/mL).
Symptoms associated with overdosage consisted mainly of agitation, drowsiness, mydriasis, sweating, shivering, nausea, and vomiting. Other symptoms observed with dexfenfluramine overdose and not noted under ADVERSE REACTIONS include cold sensation, excitation, nystagmus, garrulousness, delusions, bladder tenesmus, chattering teeth, abnormal reflexes, facial myoclonus, trismus, tonic-clonic seizures, impairment of consciousness, coma (stage 2-4), sinus bradycardia, repolarization abnormalities, right anterior hemiblock, polypnea, diffuse bronchial rales, and flushing.
Significant acute toxicity occurred at oral doses greater than 40, 70, and 75 mg/kg in rats, mice, and guinea pigs, respectively. A dose of 40 mg/kg is approximately 31 times greater than the effective anorectic dose tn rats.
Management of Overdose
General supportive measures for oral drug overdose should be instituted. Measures that have been used in dexfenfluramine overdose cases include aspiration of gastric contents, gastric lavage with activated charcoal, osmotic diuresis, forced acid diuresis, and careful monitoring of CNS or respiratory depression. The effectiveness of dialysis is not known. Patients should be followed closely until there is no further evidence of drug-related CNS effects. No specific therapy for dexfenfluramine overdose is known.
Dexfenfluramine is contraindicated in patients with diagnosed pulmonary hypertension (see WARNINGS). Dexfenfluramine is contraindicated in patients receiving monoamine oxidase inhibitors (see DRUG INTERACTIONS). Dexfenfluramine is contraindicated in patients with hypersensitivity to dexfenfluramine, fenfluramine, or related compounds.
Last reviewed on RxList: 12/8/2004
This monograph has been modified to include the generic and brand name in many instances.
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