Medications for Emesis in the Emergency Room Setting
The first-line medication for treating vomiting in the emergency room setting is ondansetron (8 mg IV or 4-8 mg oral), which offers excellent efficacy with minimal sedation and side effects compared to other antiemetics. 1
First-Line Antiemetic Options
Ondansetron: 8 mg IV (administered over 1-2 minutes) or 4-8 mg oral; can be repeated every 8 hours as needed 2, 1
- Advantages: No sedation, minimal side effects, no risk of akathisia
- Particularly effective for most causes of vomiting in the ER setting
Metoclopramide: 10 mg IV (administered slowly over 1-2 minutes) 3, 1
- Should be administered slowly to reduce risk of akathisia
- Monitor for dystonic reactions and akathisia that can develop within 48 hours
- Consider diphenhydramine 25-50 mg IV/PO for treatment of dystonic reactions 3
Second-Line Antiemetic Options
Prochlorperazine: 10 mg IV/PO every 4-6 hours as needed 4, 1
- Effective but has higher risk of akathisia than ondansetron
- Decreasing infusion rate can reduce incidence of akathisia
Promethazine: 25-50 mg IV/PR every 6 hours as needed 4
- More sedating than other options
- Risk of vascular damage with IV administration
- May be suitable when sedation is desirable
Refractory Nausea and Vomiting
Droperidol: Consider in refractory cases (limited use due to FDA black box warning regarding QT prolongation) 1
- More effective than prochlorperazine or metoclopramide but has safety concerns
Haloperidol: 1-2 mg PO/IV every 4-6 hours as needed 4
- Useful for refractory cases
Dexamethasone: 4-8 mg IV/PO as a single dose 4
- Often used in combination with other antiemetics for enhanced effect
- Particularly useful for chemotherapy-induced nausea and vomiting
Combination Therapy for Severe Cases
- For severe, refractory vomiting, consider combining medications from different classes 4:
- Serotonin antagonist (ondansetron) + dopamine antagonist (metoclopramide)
- Add dexamethasone for enhanced antiemetic effect
- Consider adding lorazepam 0.5-2 mg IV/PO for anxiety-related vomiting 4
Important Clinical Considerations
- IV administration is preferred for patients actively vomiting 4
- Antiemetics should be given slowly IV to minimize side effects 1
- Cochrane review found no definitive evidence of superiority of any one drug over another or over placebo in the ED setting, suggesting supportive care with IV fluids may be sufficient for many patients 5
- Repeat dosing of ondansetron may not provide additional benefit if the first dose was ineffective 6
Special Populations
- Pregnancy: Ondansetron is commonly used, though safety data is limited
- Pediatric patients: Ondansetron has shown efficacy in facilitating oral rehydration therapy in children with gastroenteritis 7
- Elderly: Consider starting with lower doses due to increased risk of side effects
- Hepatic impairment: Dose adjustment may be necessary for patients with severe hepatic dysfunction 8
Remember that the underlying cause of vomiting should be identified and treated when possible, as antiemetics provide symptomatic relief but do not address the underlying etiology.