Anti-Nausea Medications (Ondansetron, Metoclopramide, Domperidone)
Stop nausea and vomiting from many causes. Ondansetron is preferred when constipation is a concern; metoclopramide and domperidone also help stomach emptying.
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
Drug class
Antiemetics — multiple classes
Examples
5-HT3 antagonists: ondansetron (Zofran), granisetron. Dopamine antagonists: metoclopramide (Reglan, Primperan), domperidone (Motilium), prochlorperazine (Stemetil). Antihistamines: cyclizine. Steroids: dexamethasone (chemotherapy).
How it works
Ondansetron blocks serotonin (5-HT3) receptors in the gut and brain — most powerful for chemotherapy and post-operative nausea. Metoclopramide and domperidone block dopamine and also speed up stomach emptying. Prochlorperazine blocks dopamine for vertigo-related nausea. Different mechanisms suit different causes.
What it treats
- Acute viral or food-poisoning gastroenteritis
- Chemotherapy-induced nausea (ondansetron, dexamethasone)
- Post-operative nausea
- Migraine-associated nausea (metoclopramide first-line)
- Pregnancy nausea (selected agents — see below)
- Gastroparesis (metoclopramide, domperidone)
How to take it
Ondansetron 4-8 mg orally, dissolving tablet, or IV every 8 hours.
Metoclopramide 10 mg up to 3 times daily — limit to 5 days due to risk of movement disorders (FDA warning).
Domperidone 10 mg up to 3 times daily before meals — better safety profile than metoclopramide; needs ECG check before starting (QT interval).
Prochlorperazine 5-10 mg orally up to 3 times daily.
Common side effects
- Ondansetron: constipation, headache, dizziness
- Metoclopramide: drowsiness, restlessness, twitching
- Domperidone: dry mouth, headache, mild drowsiness
- Prochlorperazine: drowsiness, dry mouth
Serious side effects — call your doctor
Tongue thrusting, neck twisting, or other involuntary movements with metoclopramide or prochlorperazine
Acute dystonia or tardive dyskinesia — STOP medication; emergency assessment.
Heart palpitations or fainting with ondansetron or domperidone
Possible QT prolongation — see your doctor.
Severe constipation with ondansetron
Reduce dose; add laxative.
Interactions
Ondansetron and domperidone: AVOID combining with other QT-prolonging drugs (some antibiotics, antifungals, antiarrhythmics). Metoclopramide: avoid with other dopamine-blocking drugs (antipsychotics).
Monitoring
Domperidone: ECG before starting, after dose increases, periodically with long-term use. Other antiemetics: no routine monitoring for short courses.
When and how to stop
Use for shortest duration possible. Metoclopramide: maximum 5 days for nausea (FDA warning). Domperidone: lowest effective dose, shortest duration (cardiac risk). Ondansetron: as needed for nausea episodes.
Pregnancy & breastfeeding
Pyridoxine (vitamin B6) + doxylamine is first-line for pregnancy nausea (Diclectin/Diclegis). Ondansetron is generally considered safe but limited data; some studies suggest small increase in cleft palate. Metoclopramide is widely used in pregnancy. Avoid prochlorperazine in first trimester.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Which anti-nausea is best for my situation?
- How long can I safely take metoclopramide?
- Should I have an ECG before starting domperidone?
Medically reviewed by: SGA Patient Education Panel · Last reviewed 24/04/2026