What are the treatment options for managing vomiting in general practice, including medications such as Reglan (metoclopramide) and Zofran (ondansetron)?

Treatment Options for Managing Vomiting in General Practice

Ondansetron (Zofran) and metoclopramide (Reglan) are the first-line medications for managing vomiting in general practice, with the choice between them depending on the underlying cause of vomiting. 1

First-Line Treatment Options

Ondansetron (Zofran)

• Dosage: 8 mg orally or intravenously every 8-12 hours as needed 1
• Mechanism: 5-HT3 receptor antagonist
• Best for:
  • First-line for acute vomiting of various causes 2
  • Chemotherapy-induced nausea and vomiting 3
  • Radiation-induced vomiting 3
  • Postoperative nausea and vomiting 4
  • Acute gastroenteritis (especially in children) 5

Metoclopramide (Reglan)

• Dosage: 10-20 mg PO/IV every 6-8 hours 1
• Mechanism: Dopamine antagonist with prokinetic properties
• Best for:
  • Gastroparesis-related vomiting 1
  • Opioid-induced nausea 1
  • Functional dyspepsia with vomiting 3
  • "Squashed stomach syndrome" from intra-abdominal tumors 3

Second-Line Treatment Options

Prochlorperazine

• Dosage: 5-10 mg PO/IV every 6-8 hours 1
• Mechanism: Dopamine receptor antagonist
• Best for: Severe nausea and vomiting when first-line agents fail 1

Haloperidol

• Dosage: 0.5-2 mg PO/IV every 4-6 hours 1
• Mechanism: Dopamine receptor antagonist
• Best for: Opioid-induced nausea and vomiting 1

Dexamethasone

• Dosage: 4-20 mg IV/PO daily 1
• Mechanism: Corticosteroid
• Best for:
  • Chemotherapy-induced vomiting (in combination with other antiemetics) 3
  • Radiation-induced vomiting 3
  • Vomiting due to increased intracranial pressure 3

Treatment Algorithm Based on Cause of Vomiting

1. Chemotherapy-Induced Vomiting

• High emetogenic risk: Combination therapy with 5-HT3 antagonist (ondansetron) + dexamethasone + NK1 receptor antagonist (aprepitant) 3
• Moderate emetogenic risk: 5-HT3 antagonist (ondansetron) + dexamethasone 3
• Low emetogenic risk: Single agent (ondansetron or dexamethasone) 3

2. Gastroparesis/Functional Vomiting

• First-line: Metoclopramide 10-20 mg every 6 hours 1
• Alternative: Domperidone (where available)
• For refractory cases: Add erythromycin or consider gastric electrical stimulation

3. Opioid-Induced Vomiting

• First-line: Metoclopramide 10-20 mg every 6-8 hours 1
• Alternative: Haloperidol 0.5-2 mg every 4-6 hours 1
• For refractory cases: Consider opioid rotation 3

4. Acute Gastroenteritis

• First-line: Ondansetron 8 mg every 8 hours 5
• Alternative: Prochlorperazine 5-10 mg every 6-8 hours

5. Radiation-Induced Vomiting

• Total body irradiation: Ondansetron 8 mg + dexamethasone 4 mg 3
• Upper abdomen radiation: Ondansetron 8 mg ± dexamethasone 3
• Low-risk areas: Rescue therapy with ondansetron or dexamethasone 3

Management of Refractory Vomiting

1. Combine medications from different classes (e.g., ondansetron + dexamethasone + metoclopramide) 1
2. Switch to a different class if one fails 1
3. Consider continuous infusion of antiemetics for intractable vomiting 3
4. Investigate underlying causes: Electrolyte abnormalities, CNS involvement, bowel obstruction 3
5. Add benzodiazepines (lorazepam 0.5-2 mg) if anxiety contributes to vomiting 3

Important Considerations and Pitfalls

Potential Side Effects to Monitor

• Ondansetron: Headache, constipation, QT prolongation 4
• Metoclopramide: Extrapyramidal symptoms, tardive dyskinesia with chronic use 1
• Prochlorperazine: Sedation, extrapyramidal symptoms 1
• Dexamethasone: Hyperglycemia, insomnia with prolonged use 1

Common Pitfalls to Avoid

1. Using PRN dosing: Around-the-clock administration is more effective for preventing vomiting than as-needed dosing 3
2. Ignoring non-pharmacological measures: Hydration, small frequent meals, avoiding triggers
3. Failing to treat the underlying cause: Always investigate and address the root cause of vomiting
4. Overlooking drug interactions: Particularly with ondansetron and QT-prolonging medications
5. Not distinguishing between nausea and vomiting: Different mechanisms may require different approaches

Special Populations

• Pregnancy: Ondansetron is often used but benefit-risk should be carefully considered
• Elderly: Consider starting with lower doses of all agents, particularly metoclopramide and prochlorperazine
• Renal impairment: No specific dose adjustments required for most antiemetics 1
• Hepatic impairment: Dose reduction may be necessary in severe impairment 1

Remember that preventive administration of antiemetics is more effective than treating established symptoms 1. For breakthrough vomiting, intravenous administration is generally preferred over oral routes due to faster onset and greater bioavailability when the patient is actively vomiting.