Signs observed at the highest doses following studies to determine LD50 in animals were respiratory difficulties and convulsions. Return to top
Acute overdosage: neurological symptoms
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. 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. Return to top
Acute overdosage: QT changes on ECG
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. Return to top
No specific treatment for overdosage is known; treatment must be symptomatic. Return to top
Adapted from the FDA Package Insert.