What is the treatment for vomiting?

Treatment of Vomiting

Start with dopamine receptor antagonists (metoclopramide, prochlorperazine, or haloperidol) as first-line therapy, titrated to maximum benefit and tolerance, and add a 5-HT3 antagonist like ondansetron if symptoms persist after 4 weeks. 1, 2

Initial Assessment and Stabilization

Before initiating antiemetic therapy, identify and address underlying causes:

• Obtain laboratory workup: Complete blood count, serum electrolytes, glucose, liver function tests, lipase, and urinalysis to exclude metabolic causes and assess dehydration 1
• Consider additional testing for hypercalcemia, hypothyroidism, and Addison's disease if clinically indicated 1
• Perform one-time imaging: EGD or upper GI imaging to exclude obstructive lesions, but avoid repeated endoscopy 1
• Correct fluid and electrolyte abnormalities: Ensure adequate hydration (at least 1.5 L/day) and address hypokalemia, hypomagnesemia, hypochloremia, and metabolic alkalosis that commonly occur with prolonged vomiting 3, 1, 2

Critical pitfall: Never use antiemetics in suspected mechanical bowel obstruction, as this can mask progressive ileus and gastric distension 1, 2

Stepwise Pharmacologic Algorithm

First-Line: Dopamine Receptor Antagonists

Choose one of the following, titrated to effect 1, 2:

• Metoclopramide 10 mg PO/IV three times daily before meals (5-10 mg in elderly) 2, 4
• Prochlorperazine (dose varies by route and formulation) 3, 2
• Haloperidol 0.5-2 mg PO/IV every 4-6 hours 2, 4

Monitor for extrapyramidal side effects, particularly in young males and elderly patients 1, 2, 4. Metoclopramide carries a black box warning for tardive dyskinesia, though actual risk may be lower than previously estimated 2.

Second-Line: Add 5-HT3 Antagonist (After 4 Weeks)

If vomiting persists despite optimized dopamine antagonist therapy, add (do not replace) a 5-HT3 antagonist 1, 2:

• Ondansetron 4-8 mg PO/IV 2-3 times daily (maximum 16 mg per dose) 2, 4
• Granisetron 1 mg PO twice daily or 34.3 mg transdermal patch weekly 4
• Palonosetron (for chemotherapy-induced vomiting, given only on day 1) 3

Key principle: Add agents from different drug classes rather than replacing one antiemetic with another, as different neuroreceptors are involved in the emetic response 2. Ondansetron is available in sublingual form, which improves absorption in actively vomiting patients 2.

Important caveat: Ondansetron may increase stool volume/diarrhea in gastroenteritis 1, and requires QTc monitoring, especially when combined with other QT-prolonging agents 1.

Third-Line: Additional Agents for Refractory Symptoms

For persistent vomiting despite combination therapy, consider adding 3, 2, 4:

• Olanzapine 2.5-5 mg PO daily (especially effective in palliative care settings) 2, 4
• Corticosteroids (dexamethasone 8 mg PO/IV on days 2-3 for chemotherapy-induced vomiting) 3
• Benzodiazepines (lorazepam 0.5-1 mg PO/IV every 4-6 hours for anxiety-related nausea; 0.25 mg in elderly) 2, 4
• Cannabinoids (dronabinol or nabilone) for refractory symptoms 3, 2
• Continuous IV or subcutaneous infusion of antiemetics for severe cases 2, 4

Avoid long-term benzodiazepine use due to dependence risk, and taper gradually when discontinuing 4.

Route of Administration Considerations

The oral route is often not feasible due to ongoing vomiting 3, 2:

• Rectal formulations: Promethazine or prochlorperazine suppositories 2
• Intravenous therapy: Required for severe, persistent vomiting 3, 2
• Sublingual/nasal formulations: Ondansetron sublingual tablets, alprazolam sublingual forms provide acute delivery 2

Treatment of Specific Underlying Causes

Gastroparesis or Gastritis

• Proton pump inhibitors or H2 receptor antagonists for acid suppression 1, 2, 4
• Continue metoclopramide as it promotes gastric emptying 1, 5

Cannabis Hyperemesis Syndrome

• Cannabis cessation is definitive treatment (requires 6 months or 3 typical cycle lengths without vomiting for diagnosis) 1
• Do not withhold abortive and prophylactic therapy even with ongoing use, as treatments can still be effective 1
• Avoid stigmatizing patients with cannabis use 1

Cyclic Vomiting Syndrome

• Combination therapy with sumatriptan plus ondansetron is typically required to abort attacks 2
• Induce sedation using promethazine, diphenhydramine, or benzodiazepines as an effective abortive strategy 2

Chemotherapy-Induced Vomiting

For highly emetogenic chemotherapy (cisplatin ≥50 mg/m²), ondansetron 24 mg as a single oral dose administered 30 minutes prior to chemotherapy is effective, with 66% of patients experiencing zero emetic episodes in 24 hours 6. For moderately emetogenic chemotherapy, ondansetron 8 mg given 30 minutes before chemotherapy, then 8 hours later, followed by 8 mg twice daily for 2 days after completion 6.

Prophylaxis continues for 2-4 days after chemotherapy completion, with combination therapy (5-HT3 antagonist, dexamethasone, and aprepitant) 3. Note that 5-HT3 antagonists are given on day 1 only for highly emetogenic regimens, while dexamethasone and aprepitant continue through the delayed emesis period 3.

Special Population: Elderly Patients

• Reduce initial doses by 25-50% (e.g., metoclopramide 5 mg, haloperidol 0.5 mg, lorazepam 0.25 mg) 4
• Monitor closely for extrapyramidal side effects and excessive sedation 4
• Assess for dehydration and medication-induced lethargy 4

Last Resort for Intractable Symptoms

For severe, intractable vomiting that fails to respond to intensified palliative care efforts, consider palliative sedation as a last resort in end-of-life care 2, 4.