Neurokinin 1 (NK1) receptor antagonists prevent an emetic signal from being transmitted. Medications include aprepitant and rolapitant. Histamine receptor antagonists can be administered by multiple routes, including orally, intramuscularly, or rectally. Adverse effects include dry mouth, sedation, and urinary retention. Medications include dimenhydrinate and diphenhydramine. Propofol, an anesthetic medication, confers its own antiemetic properties. The 2020 Cochrane Anaesthesia Review Group review of Drugs for preventing postoperative nausea and vomiting in adults after general anaesthesia: a network meta-analysis (Review) demonstrated that combination therapy is more effective than single anti-emetic, and that dexamethasone and ondansetron (a commonly used combination) are two of the most effective anti-emetics for PONV. The review adds robust evidence of efficacy for drugs in newer classes, such as aprepitant or fosapreitant, or newer agents in familiar classes, such as ramosetron. The review does not cover the cost effectiveness of the agents included and, despite increased efficacy for newer novel agents, this may preclude their immediate utilisation in anaesthetic practice. Alternative medicine In conjunction with antiemetic medications, at least one study has found that application to the pericardium meridian 6 acupressure point produced a positive effect in relieving PONV. Another study found no statistically significant difference. The two general types of alternative pressure therapy are sham acupressure and the use of the P6 point. A 2015 study found no significant difference between the use of either therapy in the treatment or prevention of PONV. In a review of 59 studies, both therapies significantly affected the nausea aspect, but had no significant effect on vomiting. Cannabinoids have also been used for treatment of PONV, but its safety and efficacy are controversial. Epidemiology Typically, the incidence of nausea or vomiting after general anesthesia ranges between 25 and 30%. Nausea and vomiting can be extremely distressing for patients, and so is one of their major concerns. Vomiting has been associated with major complications, such as pulmonary aspiration of gastric content, and might endanger surgical outcomes after certain procedures, for example after maxillofacial surgery with wired jaws. Nausea and vomiting can delay discharge, and about 1% of patients scheduled for day surgery require unanticipated overnight admission because of uncontrolled PONV. References Further reading Blackburn, J., Spencer, R. (2015). Postoperative nausea and vomiting. Pleuvry, B. (2015). Physiology and pharmacology of nausea and vomiting. External links Anesthesia Vomiting