"A huge European trial has shown that the 70-gene assay MammaPrint can identify patients with early breast cancer who can safely skip adjuvant chemotherapy, even if they have clinical characteristics suggesting they are at high risk.
Signs observed at the highest doses following studies to determine LD50 in animals were respiratory difficulties and convulsions.
Acute overdosage in humans has not been reported. In a study of advanced metastatic cancer patients which specifically determined the maximum tolerated dose of tamoxifen in evaluating the use of very high doses to reverse multidrug resistance, acute neurotoxicity manifested by tremor, hyperreflexia, unsteady gait and dizziness were noted. These symptoms occurred within 3-5 days of beginning tamoxifen and cleared within 2-5 days after stopping therapy. No permanent neurologic toxicity was noted. One patient experienced a seizure several days after tamoxifen was discontinued and neurotoxic symptoms had resolved. The causal relationship of the seizure to tamoxifen therapy is unknown. Doses given in these patients were all greater than 400 mg/m2 loading dose, followed by maintenance doses of 150 mg/m2 of tamoxifen given twice a day.
In the same study, prolongation of the QT interval on the electrocardiogram was noted when patients were given doses higher than 250 mg/m2 loading dose, followed by maintenance doses of 80 mg/m2 of tamoxifen given twice a day. For a woman with a body surface area of 1.5 m2 the minimal loading dose and maintenance doses given at which neurological symptoms and QT changes occurred were at least 6 fold higher in respect to the maximum recommended dose.
No specific treatment for overdosage is known; treatment must be symptomatic.
Tamoxifen citrate is contraindicated in patients with known hypersensitivity to the drug or any of its ingredients.
Reduction in Breast Cancer Incidence in High Risk Women and Women with DCIS Tamoxifen is contraindicated in women who require concomitant coumarin-type anticoagulant therapy or in women with a history of deep vein thrombosis or pulmonary embolus.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 1/30/2017
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