Antiemetics are a diverse group of drugs used to treat or prevent nausea and vomiting, including that associated with cancer therapy, anaesthesia and surgery, and motion sickness. Antiemetics described here include: the dopamine antagonists’ metoclopramide and chlorpromazine hydrochloride; antihistamines such as Dimenhydrinate, Meclizine Hydrochloride & Promethazine Hydrochloride. The choice of drug depends partly on the cause of nausea and vomiting. For example, hyoscine or antihistamines are used in motion sickness where as dopamine antagonists, who act selectively on the chemoreceptor trigger zone, are in effective for the treatment of motion sickness. Conversely, nausea and vomiting associated with cancer chemotherapy is often hard to control and special regimens have been devised including the use of metoclopramide in high doses and more recently 5 HT3 antagonist and ondanesetron.

Metoclopramide Hydrochloride

Indications: nausea and vomiting in gastrointestinal disorders and treatment with cytotoxics or radiotherapy; gastro-oesophageal reflux, gastroparesis؛ pre­medication and postoperatively, aid to gastro-intestinal intubation, nausea and vomiting in migraine; see also notes above.

Contraindication: epilepsy; gastrointestinal hemorrhage, mechanical obstruction or perforation; pheochromocytoma.

Dose and Administration: Nausea and vomiting, gastro-oesophageal reflux, gastroparesis: – Adult؛ Orally, or IM, or slow IV injection10 mg 3 times daily; young، adult 15 – 19 years (under 60 Kg) 5 mg 3 times daily; Children؛ Orally, or IM, or slow IV injection, up to 1 year (up to 10 Kg) ١ mg twice daily, 1 – 3 years (10-14 Kg) 1 mg 2 – 3 times daily, 3 – 5 years (15 – 19 Kg) 2 mg 2 – 3 times daily, 5 – 9 years (20-28 Kg.) 2.5 mg I times daily, 9 – 14 years (30 Kg and over) 5 mg 3 times daily. (Usual maximum 500 micrograms/Kg daily, particularly for children and young adults). Pre-medication: – Adults, by slow I.V.، 10 mg as a single dose. Aid to gastrointestinal intubation, Orally, or IM or by slow intravenous injection, Adult 10 – 20 mg as a single dose 5 – 10 minutes before examination؛ Young Adult (15 – 19 years) 10mg; child under 3 years 1 mg، 3 – 5 years 2 mg, 5 – 9 years 2.5 mg, 9 – 14 years 5 mg.


Meclizine-Pyridoxine Hydrochloride

Indications: for the prevention and treatment of nausea, vomiting and/or vertigo associated with motion sickness; see also notes above. Contraindications: Bladder Outflow Obstruction, Chronic Idiopathic Constipation, Narrow Angle Glaucoma, Pyloroduodenal Obstruction, And Urinary Retention.

Dose and Administration: Adults & Children (>12 years of age): – Motion sickness (prophylaxis & treatment) – Oral, 25 to 50 mg one hours before travel. Dose may be repeated every twenty-four ours as needed. Vertigo (prophylaxis and treatment)- Oral, 25 to 100 mg a day as needed; in divided doses.


Indications: Motion Sickness, Nausea, Nausea and Vomiting, Prevention of Motion Sickness, Prevention of Nausea and Vomiting, Vertigo, Vomiting.

Dose and Administration: Adults: Oral، 50 to 100 mg every four to six hours. Children: Oral, 6-12 Years of age, 25 to 50 mg every six to eight hours as needed، not to exceed 150 mg per day; 2-6 years of age, 12.5 to 25 mg every six to eight hours as needed, not to exceed 75 mg per day. Note: Oral dosage forms used for motion sickness should be taken 30 minutes before motion. Contraindications: Acute Asthma Attack, Lactating Mothe, Benign Prostatic Hypertrophy, Bladder Outflow Obstruction, Chronic Idiopathic Constipation, Glaucoma, Stenosing Peptic Ulcer, And Urinary Retention.

Promethazine Hydrochloride

Indications: – control of nausea, vomiting, and vertigo of various cause, as a sedative and hypnotic, and as a common ingredient of cough and cold preparations؛ also see notes above.

Contraindications: – patients who have exhibited hypersensitivity to the drug؛ also in those who have received large doses of CNS depressants and/or in those who are comatose, in epileptic seizures.

Dose and Administration: Note: For motion sickness, the initial 25 mg dose should be taken one half to one hour before travel, and the dose repeated 8 – 12 hours later, if necessary. Adult, 25 mg initially, then 10 to 25 mg every 4 – 6 hours as needed. Children (>2 years of age); 0.25 to 0.5 mg per Kg of body weight every 4 to 6 hours or 10 to 25 mg every four to six hours as needed. IM or IV, Adults, 12.5 to 25 mg every 4 hours as needed. Children (> 2 years of age); 0.25 to 0.5 mg per Kg of body weight every 4 to 6 hours as needed. Antivertigo agent Oral, Adult, 25mg 2 times a day as needed. Children (> 2 years of age), ٠.5 mg to 1mg per kg of body weight or 10 to 25mg 2 times a day as needed.


Chlorpromazine Hydrochloride

Indications: – For the prevention and control of severe nausea and vomiting. Contraindications: – severe central nervous system depression, or severe cardiovascular diseases and hypotension.

Dose and Administration: Adults: Oral, 12.5 –25mg every 4 – 6 hours, as necessary. Slow، deep I.M.، 25 mg as a single dose, the dosage being increased to 25 – 50mg every 3 – 4 hours until vomiting stops; it is then given orally if necessary. Children (6 month and over): Oral or slow, deep I.M.، 0.55mg/kg every 6–٨ hour as necessary.

Note: Patients should remain lying down for at least 30 minutes after injection.


Indications: moderately emetogenic chemotherapy or radiotherapy; prevention of postoperative nausea and vomiting.

Contraindications: pregnancy and breast-feeding, moderate or sever hepatic impairment.

Dose and Administration: – The recommended adult oral dosage of ZOFRAN is 24 mg given as three 8-mg tablets administered 30 minutes before the start of single-day highly emetogenic chemotherapy, including cisplatin ≥ 50 mg/m2. Multiday, single-dose administration of a 24 mg dosage has not been studied. For the injection The first dose is injected 30 minutes before chemotherapy is begun. After chemo is completed, use as directed by your doctor, usually for 1 or 2 days after chemo is done.


Indications: upper gastrointestinal motility (GI) modifier, nausea and vomiting. Contraindications: – renal impairment, pregnancy and breast-feeding, gastrointestinal hemorrhage.

Dose and Administration: upper GI disorders adult: 10mg 3-4 times a day. Nausea and vomiting, 20mg 3-4 times a day. Child 2.5mg/10kg body weight 3 times daily before meals.