Antiemetic — Neurokinin 1 (NK₁) Receptor Antagonist Pregnancy: Contraindicated — teratogenic in animal studies. Ensure effective contraception (including additional method for 1 month after stopping — hormonal contraceptive efficacy reduced).

Aprepitant

Brand names: Emend

Adult dose

Dose: Chemotherapy-induced nausea and vomiting (CINV) prophylaxis — highly emetogenic regimens: Day 1: 125mg orally 1 hour before chemotherapy. Days 2–3: 80mg orally each morning. Used as part of triple antiemetic regimen: aprepitant + dexamethasone + 5-HT₃ antagonist (ondansetron or granisetron).

Route: Oral (capsules)

Frequency: Once daily for 3 days (CINV prophylaxis)

Max: 125mg (day 1); 80mg (days 2–3)

Fosaprepitant 150mg IV (prodrug of aprepitant) can be given as single IV dose on day 1 instead of oral aprepitant 3-day course — more convenient. Dexamethasone dose reduction required when co-administered with aprepitant (CYP3A4 inhibition increases dexamethasone levels — reduce dexamethasone dose by approximately 50%).

Paediatric dose

Route: Oral

Frequency: Once daily for 3 days

Max: 125mg (day 1); 80mg (days 2–3)

BNF for Children: 12–17 years: adult dose (125mg day 1, 80mg days 2–3). Children 6 months–11 years: weight-based dosing using oral suspension (specialist oncology only). Source: BNF for Children 2024. Seek specialist opinion for children under 12 years.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

Mild–moderate hepatic impairment: no adjustment. Severe hepatic impairment (Child-Pugh >9): use with caution — limited data.

Clinical pearls

Dexamethasone dose adjustment: when aprepitant is co-prescribed with dexamethasone as antiemetic, reduce dexamethasone dose by ~50% (CYP3A4 inhibition approximately doubles dexamethasone AUC).
Triple antiemetic regimen for highly emetogenic chemotherapy (MASCC/ESMO 2023): aprepitant day 1 125mg + ondansetron 8mg IV day 1 + dexamethasone 12mg day 1 then 8mg days 2–4.
Fosaprepitant IV: single 150mg IV dose on day 1 equivalent to 3-day oral aprepitant — preferred for hospitalised patients or those unable to take oral medications.
Warfarin monitoring: INR typically falls during and after aprepitant course (CYP2C9 induction reduces warfarin exposure) — monitor INR at days 7–10 and 2 weeks after completing course.

Contraindications

Concomitant pimozide, terfenadine, astemizole, or cisapride (CYP3A4 inhibition causes life-threatening arrhythmia with these substrates)
Known hypersensitivity to aprepitant

Side effects

Fatigue, asthenia
Hiccups
Constipation
Headache
Decreased appetite
Elevated liver enzymes (mild — transient)

Interactions

CYP3A4 substrates: aprepitant is a moderate CYP3A4 inhibitor — increases levels of dexamethasone (reduce dose by ~50%), methylprednisolone, midazolam, alprazolam, ciclosporin, tacrolimus
CYP3A4 inducers (rifampicin, carbamazepine, phenytoin): significantly reduce aprepitant levels — avoid
Warfarin: aprepitant induces CYP2C9 — reduces warfarin levels; INR falls 2 weeks after stopping aprepitant — monitor INR closely
Hormonal contraceptives: reduced efficacy (CYP3A4 induction) — use additional contraceptive method for 1 month after aprepitant course
Pimozide / terfenadine / astemizole / cisapride: contraindicated — fatal arrhythmia risk

Monitoring

INR (if on warfarin — days 7–10 and 2 weeks after course)
LFTs (if prolonged use or hepatic impairment)
Nausea and vomiting control (assess efficacy on days 1, 2–5 post-chemotherapy)

Reference: BNFc; BNF 90; MASCC/ESMO Antiemetic Guidelines 2023; NICE TA227 (Aprepitant for CINV); SPC Emend. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways