What are the different antiemetics and their dosages for managing nausea and vomiting?

Antiemetic Medications and Dosages for Managing Nausea and Vomiting

The most effective antiemetic regimen should be selected based on the emetogenic risk of the therapy, with triple therapy (5-HT3 antagonist + dexamethasone + NK1 antagonist) recommended for highly emetogenic chemotherapy, and dual therapy (5-HT3 antagonist + dexamethasone) for moderately emetogenic chemotherapy. 1

Classification of Antiemetics by Mechanism of Action

5-HT3 Receptor Antagonists

• Ondansetron: 16-24 mg PO or 8-12 mg IV (maximum 32 mg) day 1 2
• Granisetron: 2 mg PO or 1 mg PO bid or 0.01 mg/kg (maximum 1 mg) IV day 1; transdermal patch containing 34.3 mg applied 24-48 hours before chemotherapy 2
• Palonosetron: 0.25 mg IV day 1 (preferred for delayed emesis prevention) 2, 1
• Dolasetron: 100 mg PO or 1.8 mg/kg IV or 100 mg IV day 1 2
• Tropisetron: 5 mg PO once daily 1

NK1 Receptor Antagonists

• Aprepitant: 125 mg PO day 1, followed by 80 mg PO days 2-3 2, 3
• Fosaprepitant: 115 mg IV day 1 (substitute for aprepitant 125 mg) 2, 3
• Netupitant: Used in combination with palonosetron 1, 4
• Rolapitant: Used with granisetron or ondansetron 4

Corticosteroids

• Dexamethasone: 12 mg PO or IV day 1, then 8 mg daily for days 2-4 (for highly emetogenic chemotherapy); dose reduced by 50% when combined with aprepitant 2, 3, 5

Dopamine Receptor Antagonists

• Metoclopramide: 10-40 mg PO or IV every 4-6 hours 2, 1
• Prochlorperazine: 10 mg PO or IV every 4-6 hours; 25 mg suppository every 12 hours 2
• Domperidone: 20 mg PO 3-4 times daily 1

Benzodiazepines (Adjunctive)

• Lorazepam: 0.5-2 mg PO or IV or sublingual every 4-6 hours prn 2, 1
• Alprazolam: 0.25-0.5 mg PO three times daily (for anticipatory nausea/vomiting) 2

Antiemetic Regimens Based on Emetogenic Risk

Highly Emetogenic Chemotherapy

Triple therapy regimen:

1. 5-HT3 antagonist (day 1):
   • Palonosetron 0.25 mg IV (preferred) OR
   • Ondansetron 16-24 mg PO or 8-12 mg IV OR
   • Granisetron 2 mg PO or 1 mg PO bid or 0.01 mg/kg IV
2. Dexamethasone 12 mg PO or IV days 1-4
3. NK1 antagonist:
   • Aprepitant 125 mg PO day 1, then 80 mg PO days 2-3 OR
   • Fosaprepitant 115 mg IV day 1 2, 1

Moderately Emetogenic Chemotherapy

1. 5-HT3 antagonist (day 1):
   • Any of the above 5-HT3 antagonists
2. Dexamethasone 12 mg PO or IV day 1
3. Consider adding NK1 antagonist for select patients 2, 1

Low Emetogenic Chemotherapy

Single agent:

• Dexamethasone 12 mg PO or IV daily OR
• Metoclopramide 10-40 mg PO or IV every 4-6 hours OR
• Prochlorperazine 10 mg PO or IV every 4-6 hours 2

Minimal Emetogenic Chemotherapy

• No routine prophylaxis recommended 2

Breakthrough Nausea and Vomiting Management

For breakthrough symptoms, add an agent from a different class:

• Prochlorperazine: 10 mg PO/IV every 4-6 hours or 25 mg suppository every 12 hours
• Metoclopramide: 10-40 mg PO/IV every 4-6 hours
• Olanzapine: 2.5-5 mg PO twice daily
• Dexamethasone: 12 mg PO/IV daily (if not already using)
• Lorazepam: 0.5-2 mg PO/IV every 4-6 hours
• Dronabinol: 5-10 mg PO every 3-6 hours
• Haloperidol: 1-2 mg PO every 4-6 hours 2

Radiation-Induced Nausea and Vomiting

For upper abdominal radiation:

• Ondansetron or granisetron with or without dexamethasone 2

Anticipatory Nausea and Vomiting

• Lorazepam: 0.5-2 mg PO/IV
• Alprazolam: 0.25-0.5 mg PO three times daily
• Consider behavioral therapy techniques 2

Key Considerations and Pitfalls

1. Prevention is better than treatment: The goal is to prevent nausea/vomiting rather than treat it once it occurs 2, 1

2. Full period of risk coverage: Protection must cover the entire risk period (at least 4 days for highly emetogenic and 3 days for moderately emetogenic chemotherapy) 2

3. Drug interactions: When combining aprepitant with corticosteroids, reduce the corticosteroid dose by 50% due to drug interactions 1, 3

4. Differential diagnosis: Always rule out other causes of nausea/vomiting (electrolyte disturbances, brain metastases, opioid use, etc.) 1

5. Cardiovascular effects: Use dolasetron with caution in patients with cardiac conduction abnormalities 6

6. Hepatic impairment: Adjust ondansetron dosing in patients with hepatic impairment 6

7. Multiday chemotherapy: For multiday regimens, antiemetic therapy should be selected based on the drug with the highest emetic risk 2

8. Oral vs. IV formulations: Oral and IV antiemetic formulations have equivalent efficacy; choose based on patient's ability to take oral medications 2