A group of drugs used to prevent or relieve nausea and vomiting
Antiemetic drugs are used to prevent or relieve nausea and vomiting due to motion sickness, vertigo, migraine, Ménière’s disease, and labyrinthitis. They may also be used to relieve the nausea and vomiting that may occur during chemotherapy, radiotherapy, or after a general anaesthetic, and, more rarely, to treat severe vomiting in pregnancy (see Hyperemesis). Antiemetics are not normally used to alleviate vomiting due to food poisoning because the body needs to rid itself of harmful substances.
Antiemetic drugs work in various ways. For example, antihistamines and anticholinergics (also known as antimuscarinics) suppress the vomiting reflex; motility stimulants work by increasing movement through the gastrointestinal tract; and serotonin antagonists suppress signals to and from the vomiting centre in the brain.
There are many different types of antiemetics, each with different uses and possible side effects. They are normally taken orally but may be given by injection or as a suppository if vomiting is severe. Some are also available as skin patches.
Hyoscine hydrobromide may be prescribed as a skin patch to relieve motion sickness; it is also available over the counter as tablets. Side effects may include dry mouth, drowsiness, difficulty passing urine, and dizziness.
These drugs may be taken to ease nausea due to Ménière’s disease and labyrinthitis and to prevent motion sickness. Some types for motion sickness can be bought over the counter. Possible side effects include drowsiness, blurred vision, dry mouth, difficulty passing urine, and problems with coordination. The drugs may affect driving ability.
Domperidone is available over the counter for the relief of nausea, dyspepsia, bloating, and abdominal discomfort after a meal. It may also be prescribed to relieve nausea and vomiting due to chemotherapy, radio-therapy, or emergency contraception. Side effects are rare; they may include gastrointestinal disturbances, breast enlargement, reduced sex drive, and a rash. Metoclopramide is used to relieve nausea and vomiting due to gastrointestinal disorders such as gastro-oesophageal reflux disease, migraine, chemotherapy, or radiotherapy. Side effects include muscle spasms, especially of the face. This side effect is particularly likely to occur in young people and the drug is therefore not usually given to those under 20 years old.
These drugs may be used to treat nausea and vomiting due to radiotherapy, chemotherapy, general anaesthetics, vertigo, or labyrinthitis. They may also sometimes be used to treat severe vomiting in pregnancy. Pro-chlorperazine is available over the counter to treat nausea and vomiting due to previously diagnosed migraine in people over 18 years old. Side effects of phenothiazines include dizziness, restlessness, muscle spasms, and tremor.
These drugs are used mainly to prevent or relieve severe vomiting caused by chemotherapy or radiotherapy. They are usually started shortly before chemotherapy or radiotherapy begins and continued for up to a few days after the final dose of chemotherapy drugs or radiotherapy is given. Serotonin antagonists may also be used to prevent vomiting after surgery under general anaesthesia. They cause very few side effects.
Betahistine is used specifically to treat Ménière’s disease. It is taken orally and generally produces few side effects, the main one being gastrointestinal disturbance. Nabilone is mainly used to treat nausea and vomiting caused by chemotherapy when other antiemetic drugs have been ineffective. It commonly causes drowsiness and dizziness. It may also cause mood changes and various nervous system side effects, such as incoordination, visual disturbances, difficulty concentrating, sleeping problems, confusion, and disorientation.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.