Postoperative nausea and vomiting (PONV) is an unpleasant complication affecting about a third of the 10% of the population undergoing general anaesthesia each year.

Emetogenic drugs commonly used in anaesthesia include nitrous oxide, physostigmine and opioids. The intravenous anaesthetic propofol is currently the least emetogenic general anaesthetic. These medications are thought to stimulate the chemoreceptor trigger zone (CTZ). This area is on the floor of the fourth ventricle and is effectively outside of the blood-brain barrier. This makes it incredibly sensitive to toxin and pharmacological stimulation. There are multiple neurotransmitters such as histamine, dopamine, serotonin, acetylcholine, and the more recently discovered neurokinin-1 (substance P).