Pimozide intoxication with QT prolongation and torsades de pointes

It is well known that pimozide poisonings may cause prolongation of the QT interval and hypotension, but case reports with torsades de pointes (TdP) following an overdose are rather rare. A 38-year-old woman with paranoid schizophrenia took a total amount of 300 mg pimozide together with alcohol as a suicide attempt. On admission, 2 hours later, she was drowsy and partial agitated, her blood pressure was 110/50 mm Hg at a heart rate of 80 bpm. The ECG revealed a prolonged QTc of 0.65 sec. Toxicological analysis in serum showed a pimozide concentration of 63,7 ng/mL (therapeutic range 4-10 ng/mL), an ethanol concentration of 2.2 g/L and a lithium concentration of 0,43 mmol/L (within the therapeutic range). Minutes after admission the patient developed a self-limiting episode of TdP followed by two episodes which were terminated by electrical cardioversion with 150 J. Treatment with magnesium was started beginning with a bolus of 12 mval followed by an infusion with 1.33 mval/h.