Blood will be collected at times: 0, 15, 30, 60, 90, 120, 180, 240, 480 minutes through the cannula already in place in the standard manner. (Note time 0 is the time of paracetamol dosing). 3-6 mL of blood is collected on each occasion and then transferred into a 6 mL heparinised saline vacutainer®. These will be spun in an Eppendorf® Centrifuge 5810R at 4000 g for 5 minutes. Plasma will be removed and transferred into a 2 mL microtube (Eppendorf® safe lock) prior to freezing at –20°C. The catheter line and extension will be kept patent using heparinised saline (10 IU/ mL) flushes.