What is the best management approach for a patient experiencing nausea and vomiting?

Management of Nausea and Vomiting

Begin with dopamine receptor antagonists (metoclopramide 10 mg PO/IV three times daily, prochlorperazine, or haloperidol 0.5-2 mg every 4-6 hours) as first-line therapy, titrated to maximum benefit and tolerance, while simultaneously identifying and treating underlying causes. 1

Initial Assessment: Identify Underlying Causes

The priority is determining the etiology while initiating symptomatic treatment. Key causes to evaluate include:

• Medication-induced vomiting - Review all current medications and recent additions 1, 2
• Metabolic abnormalities - Check complete blood count, serum electrolytes, glucose, calcium, liver function tests, lipase, and thyroid function 3
• Gastrointestinal causes - Consider gastritis, gastroesophageal reflux, gastroparesis, bowel obstruction, or severe constipation 1, 2
• Cannabis hyperemesis syndrome - Obtain detailed cannabis use history, particularly in younger patients 3
• Neurologic causes - Evaluate for brain metastases, increased intracranial pressure, or vestibular disorders 1

Critical pitfall: Obtain one-time upper endoscopy or imaging to exclude obstructive lesions, but avoid repeated studies unless new symptoms develop 3

Stepwise Pharmacologic Algorithm

First-Line: Dopamine Receptor Antagonists

Start with one of the following, titrated to maximum tolerated dose:

• Metoclopramide 10 mg PO/IV three times daily - Particularly effective for gastroparesis and delayed gastric emptying 1, 3
• Prochlorperazine 10 mg PO/IV every 6-8 hours 1
• Haloperidol 0.5-2 mg PO/IV every 4-6 hours - Alternative dopamine antagonist with different receptor profile 1, 2

Monitor closely for extrapyramidal side effects, particularly in young males and elderly patients 2, 3. Treat with diphenhydramine 50 mg IV if extrapyramidal symptoms develop 3

Second-Line: Add 5-HT3 Receptor Antagonists

If symptoms persist after 4 weeks of dopamine antagonist therapy, add:

• Ondansetron 8 mg PO/IV 2-3 times daily (maximum 16 mg per dose) 1, 3, 4
• Granisetron 1 mg PO twice daily or 34.3 mg transdermal patch weekly 2

Key principle: Add agents from different drug classes rather than replacing one antiemetic with another, as different neuroreceptors mediate the emetic response 1

Monitor for QTc prolongation when using ondansetron, especially with concomitant QT-prolonging medications or electrolyte abnormalities 3, 4

Important caveat: Ondansetron may increase stool volume and diarrhea, so use cautiously if diarrhea is present 3

Third-Line: Additional Agents for Refractory Symptoms

For persistent vomiting despite combination therapy, consider adding:

• Dexamethasone 10-20 mg IV - Superior efficacy when combined with ondansetron 3
• Olanzapine 2.5-5 mg PO daily - Particularly effective in palliative care settings 2, 3
• Lorazepam 0.5-1 mg PO/IV every 4-6 hours - For anxiety-related nausea 1, 2
• Dronabinol 2.5-7.5 mg PO every 4 hours as needed - FDA-approved cannabinoid for refractory symptoms 3

Cause-Specific Treatment

Gastritis or Gastroesophageal Reflux

• Add proton pump inhibitor or H2 receptor antagonist 1, 2
• Continue metoclopramide as it promotes gastric emptying 3

Metabolic Abnormalities

• Correct hypercalcemia and electrolyte imbalances identified on laboratory testing 1, 3
• Ensure adequate hydration with at least 1.5 L/day fluid intake 3
• Thiamin supplementation to prevent Wernicke's encephalopathy in persistent vomiting 3

Prolonged Vomiting Complications

• Monitor and correct hypokalemia, hypochloremia, and metabolic alkalosis 3
• Address hypomagnesemia as it can perpetuate electrolyte disturbances 3

Administration Principles

Administer antiemetics on a scheduled basis rather than PRN, as prevention is far easier than treating established vomiting 3

Consider alternative routes (IV, rectal, sublingual) if oral route is not feasible:

• Ondansetron sublingual tablets 1
• Prochlorperazine or promethazine rectal suppositories 1
• Lorazepam sublingual or rectal formulations 1

Use multiple concurrent agents from different drug classes simultaneously rather than sequential monotherapy for refractory cases 3

Special Population Considerations

Elderly Patients

• Reduce initial doses by 25-50% for all antiemetics 2
• Start lorazepam at 0.25 mg PO 2-3 times daily 2
• Monitor closely for extrapyramidal side effects and sedation 2
• Avoid long-term benzodiazepine use due to dependence risk 1

Cancer Patients

• For chemotherapy-induced nausea and vomiting, follow specific antiemesis guidelines rather than general approaches 5, 1
• Screen at initial outpatient and inpatient visits 5
• Provide prophylaxis for acute and delayed emesis with moderate to highly emetogenic chemotherapy 5

Critical Pitfalls to Avoid

Never use antiemetics in suspected mechanical bowel obstruction - This can mask progressive ileus and gastric distension 1, 3

Avoid repeated endoscopy or imaging unless new symptoms develop 3

Do not stigmatize patients with cannabis use - Offer abortive and prophylactic therapy even with ongoing use, as treatments can still be effective 3

Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction following abdominal surgery or chemotherapy 4

Last Resort for Intractable Symptoms

For severe, intractable vomiting failing all interventions:

• Consider continuous IV or subcutaneous infusion of antiemetics 1, 2
• Palliative sedation may be considered as a last resort in end-of-life care 1, 2