Drug class · Digestive

5-HT3 receptor antagonists

Also known as: 5-HT3 antagonists, setrons

Anti-sickness medicines that block 5-HT3 receptors; ondansetron is the member covered on this site. Ondansetron is used to prevent nausea and vomiting after chemotherapy, radiotherapy and surgery. Great Ormond Street Hospital says it is used mainly for sickness caused by chemotherapy or radiotherapy, and also after operations.

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Also called
5-HT3 antagonists, setrons

Mechanism of action

They interfere with serotonin, a natural substance that can cause nausea and vomiting, by acting on 5-HT3 receptors. StatPearls describes ondansetron as a selective 5-HT3 receptor antagonist whose anti-sickness effect is thought to come mainly from blocking receptors outside the brain. The ondansetron StatPearls entry describes an additional central action on 5-HT3 receptors in the area postrema, a region of the brain stem. StatPearls says product labelling warns about combining these medicines with other medicines that act on serotonin, although the evidence is limited.

Members of the class

ondansetron

Members with a page on this site are linked.

Class effects

  • Headache
  • Constipation
  • Weakness, tiredness or drowsiness
  • Feelings of warmth or flushing, mainly in the head or over the stomach

Cautions

  • It may be given by mouth as a tablet, melt or syrup, or as an injection into a vein, according to Great Ormond Street Hospital.
  • The MHRA has warned of a small increased risk of cleft lip or palate after use of ondansetron in the first 12 weeks of pregnancy.
  • A UK leaflet says ondansetron must not be used with apomorphine.
  • An NHS prescribing sheet says ondansetron lengthens the QT interval in a dose-related way and is avoided in congenital long QT syndrome.
  • The same prescribing sheet says low blood potassium and magnesium should be corrected before ondansetron is used.
  • MedlinePlus lists vision changes and a fast, slow or irregular heartbeat among serious effects needing urgent medical attention; in the UK, call 999 in an emergency, or contact NHS 111 or a GP for advice.

Class interactions

Open the Drug Interaction Checker

Connected pages in detail

What each linked page on Anatomy Nexus covers, in a line, for 5-HT3 receptor antagonists.

Symptoms

  • Nausea The unpleasant sensation of being about to vomit.
  • Vomiting Forceful emptying of the stomach through the mouth, a protective reflex run by the brainstem that closes the airway.

Medications

  • Ondansetron Ondansetron is an anti-sickness medicine used to prevent nausea and vomiting caused by chemotherapy, radiotherapy and surgery.
Educational content. A drug class page describes what a family of medicines has in common. Individual medicines differ in dose, licensing and interactions; treatment choices belong to a prescriber.