Antiemetics They are the drugs that is effective against vomiting and nausea They are typically used to treat Motion sickness The side effects of opioid analgesics and chemotherapy directed against cancer And postoperative emesis Main classes of antiemetics Dopamine D2 antagonists Metoclopramide Domperidone Metopimazine 5 HT3 receptor antagonists Granisetron Ondansetron Dolasetron Tropisetron Antihistamines Diphenhydramine Dimenhydrinate Meclizine Cyclizine (1) Dopamine D2 receptor antagonists (1) Metoclopramide Mode of action is a potent dopamine D2 receptor antagonist used for its antiemetic and prokinetic properties Thus it is primarily used to treat nausea and vomiting, and to facilitate gastric emptying in patients with gastric stasis The anti-emetic action of metoclopramide is due to its antagonist activity at D2 receptors in the CTZ At higher doses, 5-HT3 antagonist activity may also contribute to the anti-emetic effect The prokinetic activity of metoclopramide is mediated by mascarinic activity, D2 receptor antagonist activity The prokinetic itself may also contribute to the anti-emetic effect Clinical uses (1) Antiemetic use used to treat emesis associated with conditions including: emetogenic drugs, radiation sickness, malignancy, labour, and infection considered ineffective in post-operative nausea and vomiting and ineffective for motion sickness also used by itself or in combination with paracetamol for the relief of migraine as in (2) Prokinetic use Metoclopramide increases peristalsis increases tone and amplitude of gastric contractions relaxes the pyloric sphincter so it is useful in the treamtent of gastric stasis e.g. after gastric surgery also used in gastroesophageal reflux disease (3) Other indications By inhibiting the action of prolactin inhibiting hormone (i.e. dopamine), metoclopramide has sometimes been used to stimulate lactation Contraindications It should be used with caution in Parkinson's disease since, as a dopamine antagonist, it may worsen symptoms Obstruction, perforation, or hemorrhage of the stomach or small bowel Not given in the first trimester of pregnancy Metoclopramide hydrochloride is not recommended for patients under 18 years of age Adverse effects restlessness, drowsiness, dizziness, and headache Extrapyramidal side effects as parkinsonism like symptoms Dose The usual dose is 10 milligrams 30 minutes before each meal and at bedtime Trade names (2) Domperidone Mode of action Related to that of metoclopramide Uses (1) Antiemetic use used in the treatment of nausea and vomiting It is useful in patients with Parkinson's disease because, unlike metoclopramide , domperidone does not cross the BBB (2) Lactation Domperidone, by acting as an anti-dopaminergic, results in increased prolactin secretion, and thus promotes lactation Adverse effects no extrapyramidal side effects as it does not cross BBB Dose The usual dose is 10 milligrams 30 minutes before each meal and at bedtime Trade names (2) 5 HT3 receptor antagonists (1) Granisetron Mode of action Granisetron is a serotonin5-HT3 receptor antagonist used to treat nausea and vomiting following chemotherapy It does not have much effect on vomiting due to motion sickness Clinical uses chemotherapy induced nausea and vomiting Post-operative and post-radiation nausea and vomiting Adverse effects Headache, dizziness, and constipations are the most commonly reported side effects associated with its use Dose Given intravenously about 30 minutes before beginning therapy Trade names (2) Ondansetron Mode of action Clinical uses Adverse effects As Granisetron Dose The drug is administered 1–3 times daily, depending on the severity of nausea and/or vomiting The normal dose for adults and children over the age of 12, is 8 mg initially, followed by a second dose of 8 mg, eight hours later. The drug is then administered once every 12 hours, usually not for more than 2-3 days Trade names (3) Dolasetron Mode of action Clinical uses Adverse effects Dose As Granisetron (4) Tropisetron Mode of action Clinical uses Adverse effects Dose As Granisetron Trade names