serotonin receptor antagonist serotonin receptor antagonist a serotonin antagonist, or serotonin receptor antagonist, is a drug used to inhibit the action at serotonin (5-ht) receptors. types 5-ht2a antagonists antagonists of the 5-ht2a receptor are sometimes used as atypical antipsychotics (contrast with typical antipsychotics, which are purely dopamine antagonists). they include, but are not limited to: cyproheptadine blocks 5-ht2a, h1 and is a mild anticholinergic. methysergide is a 5-ht2a antagonist and nonselective 5-ht1 receptor blocker. it causes retroperitoneal fibrosis and mediastinal fibrosis. quetiapine blocks 5-ht2a, 5-ht1a, dopamine receptors d1 and d2, histamine receptor h1, and a1 adrenoreceptors. 5-ht2a/2c antagonists ketanserin antihypertensive. blocks 5-ht2a, 5-ht2c and alpha 1 (a1) adrenoreceptors. risperidone antipsychotic trazodone nefazodone 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. they include, but are not limited to: dolasetron granisetron ondansetron palonosetron tropisetron other 5-ht3 antagonists have been considered for use in the treatment of irritable bowel syndrome: alosetron cilansetron also, the antidepressant mirtazapine acts as a 5-ht3 antagonist. non-selective 5-ht antagonists although some non-selective serotonin antagonists may have a particular affinity for a specific 5-ht receptor (and thus may be listed below e.g., methysergide), they still may also possess a generalised non-selective action. they include, but are not limited to: chlorpromazine cyproheptadine metergoline methysergide mianserin mirtazapine oxetorone pizotifen propranolol ritanserin spiperone antihistamines with antiserotonergic activity carbinoxamine cyproheptadine hydroxyzine methdilazine pizotifen promethazine pizotifen is a 5-ht2c antagonist, h1 blocker and anticholinergic useful in migraine prophylaxis. also used in the treatment of migrane. oxatomide oxetorone also used in the treatment of migrane. ketotifen others fenclonine (para-chlorophenylalanine; pcpa) an inhibitor of serotonin synthesis that has been used in the treatment of carcinoid syndrome. feverfew is a herb traditionally used for migraines (contains parthenolide). reserpine depletes serotonin stores in the brain, heart, and many other organs and has been used in hypertension and psychosis gamma-mangostin from garcinia mangostana