This week's question

A 30-year-old woman is brought to the emergency department by ambulance 2 hours after her partner found her with an empty packet of amitriptyline tablets, having ingested an estimated 1.5 g in a deliberate self-poisoning. She is drowsy but rousable to voice (GCS 13/15). Observations reveal BP 88/54 mmHg, HR 122 bpm, RR 18/min, SpO2 97% on room air, and temperature 36.8°C. Examination shows dilated pupils, dry mucous membranes, a palpable bladder and reduced bowel sounds. A 12-lead ECG demonstrates sinus tachycardia with a QRS duration of 130 ms and a terminal R wave in aVR. Which of the following is the most appropriate next step in management?