Intravenous Aprepitant for Chemotherapy-Induced Nausea and Vomiting
For patients receiving highly or moderately emetogenic chemotherapy, intravenous fosaprepitant 150 mg should be administered as a single dose on day 1 only, in combination with a 5-HT3 receptor antagonist and dexamethasone 12 mg, eliminating the need for oral aprepitant on days 2 and 3 1, 2.
Dosing Protocols by Chemotherapy Emetogenicity
Highly Emetogenic Chemotherapy (HEC)
Day 1 Administration:
- Fosaprepitant 150 mg IV (single dose, infused over 20-30 minutes) OR
- Aprepitant 130 mg IV (HTX-019 formulation, can be given as 2-minute injection or 30-minute infusion) 3
- 5-HT3 receptor antagonist (palonosetron 0.25 mg IV, ondansetron 8-16 mg IV, or granisetron 1 mg IV)
- Dexamethasone 12 mg IV or oral (reduced from 20 mg due to CYP3A4 inhibition by aprepitant) 1, 4
Days 2-4:
- Dexamethasone 8 mg oral or IV once daily 4
- No additional NK1 antagonist needed with fosaprepitant 150 mg regimen 2, 5
Moderately Emetogenic Chemotherapy (MEC)
Day 1:
- Same as HEC regimen above
- For anthracycline-cyclophosphamide (AC) combinations: treat as highly emetogenic 6, 4
Days 2-3:
- Dexamethasone 8 mg oral or IV once daily 4
Alternative Oral Aprepitant Regimen
If oral aprepitant is chosen instead of IV fosaprepitant:
- Day 1: Aprepitant 125 mg oral + 5-HT3 RA + dexamethasone 12 mg
- Days 2-3: Aprepitant 80 mg oral + dexamethasone 8 mg 1, 7
For multi-day chemotherapy (e.g., 5-day cisplatin regimens):
- Day 3: Aprepitant 125 mg
- Days 4-7: Aprepitant 80 mg (with 5-HT3 RA days 1-5 and dexamethasone days 1-2) 1
Critical Safety Precautions
Drug-Drug Interactions
Dexamethasone dose reduction is mandatory: Fosaprepitant, aprepitant, and netupitant inhibit CYP3A4 metabolism, increasing dexamethasone concentrations by approximately 2-fold 1, 8. The dexamethasone dose must be reduced from 20 mg to 12 mg on day 1 when combined with NK1 antagonists. Failure to reduce dexamethasone risks excessive corticosteroid exposure 8.
Infusion-Site Reactions
- Fosaprepitant 150 mg: 2.7% incidence of infusion-site pain, erythema, or thrombophlebitis 5
- HTX-019 (aprepitant IV): Well-tolerated with both 2-minute injection and 30-minute infusion; no infusion-site reactions within 30 minutes of administration 3
- Administer over 20-30 minutes for fosaprepitant to minimize infusion-site reactions 5
Contraindications and Monitoring
- Do not use with pimozide (risk of QT prolongation)
- Monitor patients on warfarin closely (aprepitant affects CYP3A4 metabolism)
- Reduce doses of CYP3A4 substrates (e.g., certain chemotherapy agents, benzodiazepines) 9
- Rolapitant has extended half-life: do not administer more frequently than every 2 weeks 1
Administration Technique
Fosaprepitant 150 mg
- Reconstitute and dilute per manufacturer instructions
- Infuse over 20-30 minutes on day 1 only
- Administer 30 minutes before chemotherapy 5
HTX-019 (Aprepitant 130 mg IV)
- Can be administered as 2-minute IV push or 30-minute infusion
- Both methods equally safe and effective 3
- 2-minute injection offers convenience without compromising safety
- Administer before 5-HT3 antagonist and chemotherapy
Key Clinical Advantages
The single-dose fosaprepitant 150 mg regimen is non-inferior to the 3-day oral aprepitant regimen for preventing both acute and delayed CINV 5. This approach:
- Ensures adherence (no need for days 2-3 oral dosing)
- Maintains >90% NK1 receptor occupancy in CNS for 48+ hours 10
- Simplifies antiemetic management
- Particularly valuable for patients with swallowing difficulties or poor oral intake
Common Pitfalls to Avoid
- Forgetting to reduce dexamethasone dose when using NK1 antagonists—this is the most critical error 1, 8
- Using fosaprepitant 115 mg (which substitutes only day 1 of oral aprepitant) when fosaprepitant 150 mg (single-dose regimen) is preferred 2
- Administering additional NK1 antagonist on days 2-3 when fosaprepitant 150 mg was given on day 1 5
- Not considering cost barriers—aprepitant formulations can be expensive, affecting 27% of patients in one study 11