Antiemetic — Neurokinin 1 (NK₁) Receptor Antagonist Pregnancy: Should not be used during pregnancy unless clearly necessary; no clinical data on exposed pregnancies. Breast-feeding not recommended during treatment (excreted in milk of lactating rats; human excretion unknown).

Aprepitant

Brand names: Emend

Aprepitant is an oral antiemetic used, in combination with a corticosteroid and a 5-HT3 receptor antagonist, to prevent acute and delayed nausea and vomiting associated with moderately and highly emetogenic chemotherapy.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 125 mg on Day 1, then 80 mg once daily on Days 2 and 3

Route: oral

Frequency: once daily for 3 days

Given as part of a 3-day regimen for prevention of chemotherapy-induced nausea and vomiting, in combination with a corticosteroid and a 5-HT3 antagonist. 125 mg orally once daily one hour before start of chemotherapy on Day 1, and 80 mg orally once daily on Days 2 and 3 in the morning. Co-administered dexamethasone regimen: highly emetogenic chemotherapy — dexamethasone 12 mg orally Day 1, 8 mg orally Days 2-4; moderately emetogenic chemotherapy — dexamethasone 12 mg orally Day 1 only. The dose of dexamethasone accounts for active substance interactions. Capsule swallowed whole; may be taken with or without food. No dose adjustment for elderly, gender, renal impairment (including haemodialysis), or mild hepatic impairment; use with caution in moderate/severe hepatic impairment (limited/no data).

Dose adjustments

Renal

No dose adjustment necessary for renal impairment or for end-stage renal disease undergoing haemodialysis.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Co-administration with pimozide, terfenadine, astemizole or cisapride

Side effects

Hiccups
Alanine aminotransferase (ALT) increased
Dyspepsia
Constipation
Headache
Decreased appetite
Fatigue

Interactions

Aprepitant (125/80 mg) is a substrate, moderate inhibitor and inducer of CYP3A4, and an inducer of CYP2C9
As a moderate CYP3A4 inhibitor, can increase plasma concentrations of co-administered CYP3A4 substrates (total exposure of oral CYP3A4 substrates may rise up to ~3-fold during the 3-day treatment)
Must not be used concurrently with pimozide, terfenadine, astemizole or cisapride
Use with caution with CYP3A4 substrates of narrow therapeutic range (ciclosporin, tacrolimus, sirolimus, everolimus, alfentanil, ergot alkaloids, fentanyl, quinidine); particular caution with irinotecan
Warfarin (CYP2C9 substrate): monitor INR closely during and for 14 days after each 3-day course
Efficacy of hormonal contraceptives may be reduced during and for 28 days after administration — use non-hormonal back-up contraception during treatment and for 2 months after the last dose

Clinical monograph

How it works

It is a selective neurokinin-1 (NK1) receptor antagonist that blocks the action of substance P at central NK1 receptors involved in the vomiting reflex.

Prescribing in practice

Aprepitant is a moderate inhibitor and inducer of CYP3A4, causing clinically important interactions, including reduced efficacy of hormonal contraceptives and altered exposure of co-administered CYP3A4 substrates such as certain chemotherapy agents and corticosteroids.
It should be used as part of a combination antiemetic regimen rather than as monotherapy, with the corticosteroid dose reduced to account for the interaction.
Use with caution in significant hepatic impairment as experience is limited in severe disease.

Monitoring

No specific laboratory monitoring is mandated, but review for adequacy of emesis control and for interactions with concurrent medicines.

Counselling the patient

Start before your chemotherapy and continue the full course as directed.
Use an additional or alternative method of contraception, as hormonal contraceptives may be less reliable.
Tell your team about all other medicines you take, as interactions are common.

Evidence & guidelines

NK1 receptor antagonists added to standard antiemetic therapy improve control of chemotherapy-induced nausea and vomiting in randomised trials and are recommended in oncology antiemetic guidelines.

Reference: MASCC/ESMO Antiemetic Guidelines 2023; NICE TA227 (Aprepitant for CINV); SPC Emend; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways