MRCP2-0632

A 25-year-old woman presents to the emergency department after her flatmate found her drowsy in her bedroom. She had been incontinent of urine.

On examination the patient is obtunded with a Glasgow Coma Score of 7 (E1V2M4). The pupils are 7mm bilaterally and sluggishly reactive to light. The heart rate is 133 bpm and the blood pressure is 99/65 mmHg.

A 12-lead ECG reveals sinus tachycardia with a QT interval of 510 ms. The QRS duration is 115ms.

What is the most likely cause for this patient’s presentation?