What anti-emetic (anti-vomiting) medication can be prescribed for emesis (vomiting)?

Antiemetic Medication Recommendations

For general nausea and vomiting in non-chemotherapy settings, ondansetron (8 mg IV or 4-8 mg oral every 8 hours) should be your first-line choice due to its superior efficacy and minimal side effects compared to other antiemetics. 1

First-Line Treatment Approach

Ondansetron is the preferred initial antiemetic because it offers excellent efficacy with minimal sedation and avoids the akathisia risk associated with dopamine antagonists like prochlorperazine or metoclopramide. 1, 2

• Dosing: 8 mg IV or 4-8 mg oral, repeated every 8 hours as needed 1
• This agent is FDA-approved for prevention of nausea and vomiting in multiple settings including chemotherapy, radiation therapy, and postoperative contexts 3
• Ondansetron demonstrates superior effectiveness compared to promethazine, prochlorperazine, and metoclopramide in emergency department settings 2

Second-Line Options When Ondansetron Fails

If ondansetron alone is insufficient, add an agent from a different drug class rather than increasing the ondansetron dose:

Prochlorperazine (Dopamine Antagonist)

• Dose: 10 mg IV/PO every 4-6 hours as needed 1
• Important caveat: Higher risk of akathisia (restlessness) than ondansetron, which can occur up to 48 hours after administration 1, 2
• Treat akathisia with IV diphenhydramine if it develops 2

Promethazine (Antihistamine)

• Dose: 25-50 mg IV/PR every 6 hours as needed 1
• More sedating than other options—use when sedation is actually desirable 1, 2
• Critical warning: Risk of vascular damage with IV administration; consider rectal route 2

Refractory Cases Requiring Escalation

For severe or persistent vomiting despite the above measures:

Add Dexamethasone

• Dose: 4-8 mg IV/PO as a single dose 1
• Significantly enhances antiemetic effect when combined with ondansetron 4, 5
• This combination is standard for chemotherapy-induced nausea but applies to refractory cases in general 4

Consider Haloperidol

• Dose: 1-2 mg PO/IV every 4-6 hours as needed 1
• Reserved for truly refractory cases 1

Special Considerations for Your Mother

Route of Administration

• If actively vomiting: Use IV route; oral medications won't be absorbed effectively 1, 6
• Administer IV antiemetics slowly to minimize side effects 1

Elderly Patient Adjustments

• Consider lower doses due to increased risk of side effects in elderly patients 1
• Monitor more carefully for QT prolongation with ondansetron, though this risk is generally low 7

Combination Therapy Algorithm

For severe vomiting, use medications from different classes simultaneously: 1, 6

1. Start with ondansetron (serotonin antagonist) 8 mg IV
2. Add dexamethasone 4-8 mg IV for enhanced effect
3. If still inadequate, add metoclopramide 10 mg IV (dopamine antagonist) OR prochlorperazine 10 mg IV

Common Pitfalls to Avoid

• Don't use promethazine IV without extreme caution due to tissue damage risk; rectal administration is safer 2
• Don't assume akathisia is anxiety—it can develop hours after prochlorperazine or metoclopramide administration and requires diphenhydramine treatment 2
• Don't use PRN (as-needed) dosing for persistent vomiting—scheduled administration prevents breakthrough symptoms more effectively 6
• Don't forget to address underlying causes—ensure adequate hydration and correct electrolyte abnormalities 4, 6

Context-Specific Recommendations

If Chemotherapy-Related

Use triple therapy: NK1 antagonist (aprepitant) + 5-HT3 antagonist (ondansetron) + dexamethasone 4

If Pregnancy-Related

Metoclopramide and antihistamines are first-line (ondansetron is second-line in pregnancy) 7

If Postoperative

Ondansetron 4 mg IV is FDA-approved and highly effective 3, 8