Serotonin antagonist

A serotonin antagonist is a drug used to inhibit the action at serotonin (5-HT) receptors.

Types

5-HT_2A antagonists

Antagonists of the 5-HT_2A receptor are sometimes used as atypical antipsychotics (contrast with typical antipsychotics, which are purely dopamine antagonists). They include:

Cyproheptadine blocks 5-HT_2A, H1 and is a mild anticholinergic.
Methysergide is a 5-HT_2A antagonist and nonselective 5-HT₁ receptor blocker. It causes retroperitoneal fibrosis and mediastinal fibrosis.^{[citation needed]}
Quetiapine blocks 5-HT_2A, 5-HT_1A, dopamine receptors D₁ and D₂, histamine receptor H1, and A1 adrenoreceptors.

5-HT_2A/2C antagonists

Ketanserin Antihypertensive. Blocks 5-HT_2A, 5-HT_2C and Alpha 1 (A1) adrenoreceptors.
Risperidone antipsychotic
Trazodone antidepressant
Clozapine antipsychotic. Blocks 5-HT_2A, 5-HT_2C and D₄ receptors.

5-HT₃ antagonists

Another subclass consists of drugs selectively acting at the 5-HT₃ receptors, and thus are known as 5-HT₃ antagonists. They are efficacious in treating chemotherapy-induced emesis and postoperative nausea and vomiting.^[1] They include:

Other 5-HT₃ antagonists are used for the treatment of irritable bowel syndrome:

Non-selective 5-HT antagonists

Please note, that although some non-selective serotonin antagonists may have an particular affinity for a specific 5-HT receptor (and thus may be listed above e.g. methysergide), they still may also possess a generalised non-selective action.