Palonosetron (INN, trade name Aloxi) is a 5-HT3 antagonist used in the prevention and treatment of postoperative and chemotherapy-induced nausea and vomiting (PONV and CINV). Palonosetron is a 5-HT3 receptor antagonist with a strong binding affinity for this receptor and little or no affinity for other receptors. Cancer chemotherapy may be associated with a high incidence of nausea and vomiting, particularly when certain agents, such as cisplatin, are used. 5-HT3 receptors are located on the nerve terminals of the vagus in the periphery and centrally in the chemoreceptor trigger zone of the area postrema. It is thought that chemotherapeutic agents produce nausea and vomiting by releasing serotonin from the enterochromaffin cells of the small intestine and that the released serotonin then activates 5-HT3 receptors located on vagal afferents to initiate the vomiting reflex. Postoperative nausea and vomiting is influenced by multiple patients, surgical and anesthesia-related factors and is triggered by the release of 5-HT in a cascade of neuronal events involving both the central nervous system and the gastrointestinal tract. The 5-HT3 receptor has been demonstrated to selectively participate in the emetic response. The most common adverse effects are a headache, which occurs in 4–11% of patients, and constipation in up to 6% of patients. In less than 1% of patients, other gastrointestinal disorders occur, as well as sleeplessness, first- and second-degree atrioventricular block, muscle pain and shortness of breath. Palonosetron is similarly well tolerated as other sections, and slightly less than placebo.

Alosetron, marketed under the brand name Lotronex, is a 5-HT3 antagonist used for the management of severe diarrhea-predominant irritable bowel syndrome (IBS) in women only. Alosetron is a potent and selective 5-HT3 receptor antagonist. 5-HT3 receptors are nonselective cation channels that are extensively distributed on enteric neurons in the human gastrointestinal tract, as well as other peripheral and central locations. Activation of these channels and the resulting neuronal depolarization affect the regulation of visceral pain, colonic transit and gastrointestinal secretions, processes that relate to the pathophysiology of irritable bowel syndrome (IBS). 5-HT3 receptor antagonists such as alosetron inhibit activation of non-selective cation channels which results in the modulation of the enteric nervous system. Alosetron is used for the treating women with severe irritable bowel syndrome (IBS) accompanied by severe diarrhea (usually lasting for 6 months or more). It is only prescribed to women who do not respond to other medicines and is not to be used by women whose main IBS problem is constipation.

Sevoflurane is a general anesthetic that is FDA approved for the induction and maintenance of general anesthesia in adult and pediatric patients for inpatient and outpatient surgery. Sevoflurane induces a reduction in junctional conductance by decreasing gap junction channel opening times and increasing gap junction channel closing times. Sevoflurane also activates calcium dependent ATPase in the sarcoplasmic reticulum by increasing the fluidity of the lipid membrane. It also appears to bind the D subunit of ATP synthase and NADH dehydogenase and also binds to the GABA receptor. Common adverse reactions include cardiovascular: bradyarrhythmia, hypotension, gastrointestinal: nausea, vomiting, neurologic: somnolence, psychiatric: agitation, respiratory: cough, interrupted breathing and other: shivering.

Granisetron is a selective inhibitor of type 3 serotonergic (5-HT3) receptors. The drug is structurally and pharmacologically related to ondansetron, another selective inhibitor of 5-HT3 receptors. The serontonin 5-HT3 receptors are located on the nerve terminals of the vagus in the periphery, and centrally in the chemoreceptor trigger zone of the area postrema. The temporal relationship between the emetogenic action of emetogenic drugs and the release of serotonin, as well as the efficacy of antiemetic agents suggest that chemotherapeutic agents release serotonin from the enterochromaffin cells of the small intestine by causing degenerative changes in the GI tract. The serotonin then stimulates the vagal and splanchnic nerve receptors that project to the medullary vomiting center, as well as the 5-HT3 receptors in the area postrema, thus initiating the vomiting reflex, causing nausea and vomiting. Granisetron is a potent, selective antagonist of 5-HT3 receptors. The antiemetic activity of the drug is brought about through the inhibition of 5-HT3 receptors present both centrally (medullary chemoreceptor zone) and peripherally (GI tract). This inhibition of 5-HT3 receptors in turn inhibits the visceral afferent stimulation of the vomiting center, likely indirectly at the level of the area postrema, as well as through direct inhibition of serotonin activity within the area postrema and the chemoreceptor trigger zone. Granisetron is used for the prevention of nausea and vomiting associated with initial and repeat courses of emetogenic cancer therapy (including high dose cisplatin), postoperation, and radiation (including total body irradiation and daily fractionated abdominal radiation).

Ondansetron (ZOFRAN®) is a selective 5-HT3 receptor antagonist. It is effective in the treatment of nausea and vomiting caused by radiotherapy, anesthesia, surgery or cytotoxic chemotherapy drugs, including cisplatin, and has reported anxiolytic and neuroleptic properties. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist. It is not certain whether ondansetron's antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine. The released serotonin may stimulate the vagal afferents through the 5-HT3 receptors and initiate the vomiting reflex.

Metoclopramide is a dopamine D2 antagonist that is used as an antiemetic. Metoclopramide inhibits gastric smooth muscle relaxation produced by dopamine, therefore increasing cholinergic response of the gastrointestinal smooth muscle. It accelerates intestinal transit and gastric emptying by preventing relaxation of gastric body and increasing the phasic activity of antrum. Simultaneously, this action is accompanied by relaxation of the upper small intestine, resulting in an improved coordination between the body and antrum of the stomach and the upper small intestine. Metoclopramide also decreases reflux into the esophagus by increasing the resting pressure of the lower esophageal sphincter and improves acid clearance from the esophagus by increasing amplitude of esophageal peristaltic contractions. Metoclopramide's dopamine antagonist action raises the threshold of activity in the chemoreceptor trigger zone and decreases the input from afferent visceral nerves. Studies have also shown that high doses of metoclopramide can antagonize 5-hydroxytryptamine (5-HT) receptors in the peripheral nervous system in animals. Metoclopramide is used for the treatment of gastroesophageal reflux disease (GERD). It is also used in treating nausea and vomiting, and to increase gastric emptying.

Lerisetron is a 5-hydroxytryptamine3 receptor antagonist. It was under development by FAES Farma for the potential treatment of emesis resulting from chemotherapy. Lerisetron specifically binds to 5-HT3 receptors, located peripherally on vagus nerve terminals and centrally in the chemoreceptor trigger zone (CTZ) of the area postrema, which may result in suppression of chemotherapy-induced nausea and vomiting. Lerisetron had been in phase III clinical trials for the treatment of emesis. However, this study was discontinued.

Pumosetrag is a novel, orally active and selective 5-HT 3 agonist. It is a partial agonist in rats and guinea-pig and a full agonist in the mouse, suggesting important species differences in 5-HT3 receptor structure. Pumosetrag had been in phase II clinical trials for the treatment of gastroesophageal reflux disease and irritable bowel syndrome. No serious adverse events were reported. Diarrhea was not more common on the drug and only one subject experienced pruritus. All researches on this drug candidate are discontinued.

Phenyl biguanide (phenylbuguanide, PBG) is a 5-hydroxytryptamine receptor 3 agonist used to study the role of serotonin receptors in the central nervous system. It has been found to trigger dopamine release in the nucleus accumbens of rats. Phenylbiguanide is used to make amanozine.