MRCP2-0647

MRCP2-0647

A 28-year-old man is brought to the Emergency Department following a suspected deliberate overdose. On arrival, he is drowsy with a GCS of 13/15 (E3V4M6) and confused. His airway is currently patent. The respiratory rate is 30 breaths per minute although oxygen saturations are 98% on 2L/min oxygen. The chest is clear to auscultation. Heart rate is 108 bpm and blood pressure is 96/48 mmHg. The ECG shows sinus tachycardia only. He complains of severe abdominal pain and is groaning on examination. There is significant tenderness in the right upper quadrant. Bowel sounds are hyperactive. Neurological examination is difficult but discloses downgoing plantars and reactive, mid-size pupils.

Blood tests show:

Haemoglobin 112g/L Sodium 131 mmol/L Glucose 17.8 mmol
MCV 96 fL Potassium Haemolysed Lactate 5.3mmol/L
White cells 15.7×109/L Urea 15.6 mmol/L pH 7.14
Neutrophils 13.7×109/L Creatinine 207 mol/L pCO2 2.9kPa
Platelets 278×109/L ALP 234U/L pO2 19.2kPa
INR 1.2 ALT 2453U/L Bicarbonate 9.4mmol/L
PT 14 secs AST 3109U/L Base excess -15.4mEq/L
APTT 49.2secs Bilirubin 36mol/L Anion gap 30.8

The laboratory comments there is significant haemolysis of the samples.

He has a massive vomit whilst being assessed, of black liquid and fresh blood.

Which of the following drugs is this patient most likely to have overdosed upon?