Anti-emetic drugs

Anti-emetic drugs

Drug-induced emesis can now be largely controlled with anti-emetic drugs, however, nausea remains a very significant clinical problem. This dichotomy suggests that different mechanisms underlie nausea and vomiting.

Major classes of anti-emetic drugs:

5-HT3 receptor antagonists- ‘setrons’ e.g. ondansetron and palonosetron which are used to suppress chemotherapy- and radiation-induced emesis and post-operative nausea and vomiting. These drugs are not effective against motion sickness, or vomiting induced by agents increasing dopaminergic transmission. Drug action can be improved by co-administration of a corticosteroid or neurokinin 1 (NK1) receptor antagonist (see below).

Muscarinic acetylcholine receptor antagonists- e.g. hyosine (scopolamine), used for prophylaxis and treatment of motion sickness. Many side-effects including sedation and parasympathimimetic action (blurred vision, urinary retention, dry mouth).

Histamine H1 receptor antagonists- e.g. cyclizine, cinnarizine and many others, used for prophylaxis and treatment of motion sickness, vertigo and acute labyrinthitis and nausea and vomiting caused by irritants in the stomach. Concomittant antagonism of muscarinic receptors by these agents likely contributes to their activity. Side-effects include CNS depression and sedation.

Dopamine receptor antagonists- e.g. domperidone and metoclopramide, used to treat drug-induced vomiting and vomiting in gastrointestinal disorders. Phenothiazines (antipsychotics, e.g. chlorpromazine and prochlorperazine) which owe part of their action to dopamine D2 receptor antagonism are used for severe nausea and vomiting.

NK1 receptor antagonists- e.g. aprepitant, its prodrug fosaprepitant, and netupitant, used in combination with a 5-HT3 receptor antagonist and dexamethasone in the acute phase of highly emetogenic chemotherapy.

Cannabinoid (CB1) receptor agonists- e.g. nabilone, used for treatment of nausea and vomiting caused by cytotoxic chemotherapy that is unresponsive to other anti-emetics. May cause dizziness and drowsiness, impairing physical or mental abilities. Can also cause tachycardia and/or orthostatic hypotension, so caution is advised if prescribing to patients with cardiovascular disease.

Physiology and Pharmacology of Nausea and Emesis

This is an 18 slide presentation covering the physiology underlying nausea and vomiting, and the pharmacology of pro- and anti-emetic drugs. Provided by Prof. JA Peters, University of Dundee School of Medicine.

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