What are the recommended anti-emetic (antiemetic) medications and dosages for managing nausea and vomiting?

Antiemetic Medications: Recommended Agents and Dosing

First-Line Antiemetic Selection

For most clinical scenarios requiring antiemetic therapy, ondansetron 8 mg IV or 8-16 mg PO is the preferred first-line agent due to its superior efficacy, favorable safety profile, and lack of sedation or extrapyramidal side effects. 1, 2, 3

Specific Clinical Scenarios and Dosing

Chemotherapy-Induced Nausea and Vomiting (CINV)

High Emetogenic Risk Chemotherapy (e.g., cisplatin ≥50 mg/m²):

• Triple therapy is mandatory: Palonosetron 0.25 mg IV (preferred 5-HT3 antagonist) + Dexamethasone 12 mg PO/IV + Aprepitant 125 mg PO on day 1, followed by aprepitant 80 mg PO days 2-3 4, 1
• Alternative 5-HT3 antagonist if palonosetron unavailable: Ondansetron 24 mg PO as single dose 30 minutes before chemotherapy 2
• Critical dosing note: When combining aprepitant with dexamethasone, reduce dexamethasone dose to 50% due to CYP3A4 interaction 5, 1

Moderate Emetogenic Risk Chemotherapy:

• Ondansetron 8 mg PO 30 minutes before chemotherapy, then 8 mg 8 hours later, followed by 8 mg twice daily for 1-2 days after completion 2
• Add dexamethasone 12 mg PO/IV day 1 for enhanced efficacy 1
• Consider adding aprepitant 125 mg day 1, then 80 mg days 2-3 in select patients 1

Low Emetogenic Risk Chemotherapy:

• Single antiemetic agent sufficient: Ondansetron 8 mg PO before chemotherapy 5, 1
• No routine prophylaxis needed after day 1 5

Radiation-Induced Nausea and Vomiting

Upper Abdomen Radiation:

• Ondansetron 8 mg PO 1-2 hours before radiotherapy, with subsequent 8 mg doses every 8 hours after first dose for 1-2 days after completion 5, 2
• Alternative: Granisetron 2 mg PO with or without dexamethasone 4 mg PO daily 5

Total Body Irradiation:

• Ondansetron or granisetron, either with or without dexamethasone 5, 2

Postoperative Nausea and Vomiting (PONV)

Adults:

• Ondansetron 16 mg PO administered 1 hour before induction of anesthesia 2
• IV alternative: Ondansetron 8 mg IV 2

Pediatrics (4-11 years):

• Ondansetron 0.1 mg/kg IV (0.075-0.15 mg/kg range) 6
• Superior to droperidol, metoclopramide, and prochlorperazine 6

Opioid-Induced Nausea and Vomiting

• Ondansetron 8 mg IV provides complete control of emesis in 62% of patients 7
• Ondansetron 16 mg IV increases complete control to 69% and provides better nausea control (19% vs 7% with placebo) 7
• Treat on occurrence rather than prophylactically based on observed incidence 7

Emergency Department/Acute Nausea

• Ondansetron 8 mg IV is recommended as first-line therapy due to safety profile and lack of akathisia or sedation 3
• Alternative agents if ondansetron fails: Prochlorperazine or metoclopramide (monitor for akathisia) 3
• Promethazine reserved for cases where sedation is desirable, but carries risk of vascular damage with IV administration 3

Alternative Antiemetic Agents and Dosing

5-HT3 Receptor Antagonists (Comparable Efficacy)

• Granisetron: 1-2 mg PO or 1 mg IV 5, 1
• Dolasetron: 100 mg PO or IV 5, 1
• Tropisetron: 5 mg IV 5
• Palonosetron: 0.25 mg IV only (no oral formulation; preferred for high emetogenic chemotherapy) 4

Corticosteroids

• Dexamethasone: 20 mg IV for cisplatin-induced emesis; 8 mg IV for cyclophosphamide/anthracycline-based chemotherapy; given twice daily for delayed emesis 5, 1
• Prednisolone 100-150 mg or methylprednisolone 100 mg are alternatives 5

Dopamine Antagonists (3-4 times daily dosing)

• Metoclopramide: 20-30 mg PO/IV 5
• Prochlorperazine: 10-20 mg PO/IV 5
• Domperidone 20 mg or metopimazine 15-30 mg 5

Neurokinin-1 Antagonist

• Aprepitant: 125 mg PO day 1, then 80 mg PO days 2-3 5, 1
• Fosaprepitant 115 mg IV can substitute for aprepitant on day 1 1

Management of Refractory and Special Cases

Refractory Nausea/Vomiting

• Add dopamine antagonist (metoclopramide) to existing 5-HT3 antagonist + corticosteroid regimen 5, 1
• Consider switching to different 5-HT3 antagonist 1
• Full-dose IV combination: corticosteroids + 5-HT3 antagonist + dopamine antagonist 5, 1

Anticipatory Nausea/Vomiting

• Lorazepam 0.5-2 mg PO/IV/sublingual 1
• Alternative: Alprazolam 0.25-0.5 mg PO three times daily, starting night before treatment 5
• Behavioral techniques and guided imagery 5

Delayed Emesis (1-5 days post-chemotherapy)

• Continue aprepitant days 2-3 if used on day 1 1
• Dexamethasone twice daily 5
• Consider adding metoclopramide to dexamethasone 1

Multiday Chemotherapy Regimens

• 5-HT3 antagonist administered each day before first dose of moderately or highly emetogenic chemotherapy 5
• Dexamethasone once daily for every day of chemotherapy, plus 2-3 days after for regimens causing significant delayed emesis 5
• Do not add dexamethasone when chemotherapy regimen already includes corticosteroid 5

Critical Safety Considerations

QT Prolongation Risk

• Avoid ondansetron in patients with congenital long QT syndrome 2
• ECG monitoring recommended in patients with electrolyte abnormalities (hypokalemia, hypomagnesemia), congestive heart failure, or bradyarrhythmias 2
• High-dose ondansetron (32 mg IV) associated with QT prolongation; use lower doses 1

Extrapyramidal Side Effects

• Prochlorperazine and metoclopramide can cause akathisia developing any time over 48 hours post-administration 3
• Decrease infusion rate to reduce akathisia incidence 3
• Treat with IV diphenhydramine if akathisia occurs 3
• Dopamine antagonists particularly problematic in children 8

Hepatic Impairment

• In severe hepatic impairment (Child-Pugh ≥10), do not exceed 8 mg total daily dose of ondansetron 2

Drug Interactions

• Ondansetron contraindicated with concomitant apomorphine due to risk of profound hypotension and loss of consciousness 2
• Aprepitant metabolized via CYP3A4; reduce corticosteroid dose to 50% when combined 5, 1

Serotonin Syndrome

• Development reported with 5-HT3 antagonists, especially with concomitant serotonergic drugs 2

Route of Administration

• Oral and IV formulations have equivalent efficacy; use oral when possible 5, 1
• IV administration preferred when patient actively vomiting, as it produces larger improvements in nausea scores 1
• Antiemetics should be given prophylactically 30-60 minutes before chemotherapy 5, 1