NK1 Receptor Antagonist (Antiemetic) Pregnancy: Aprepitant should not be used during pregnancy unless clearly necessary; no clinical data on exposed pregnancies are available and reproductive toxicity has not been fully characterised. Breast-feeding is not recommended during treatment (aprepitant is excreted in the milk of lactating rats; human excretion unknown). Women of childbearing potential: hormonal contraceptive efficacy 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.

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 orally once daily one hour before the start of chemotherapy on Day 1, then 80 mg orally once daily on Days 2 and 3 (in the morning)

Route: Oral - hard capsule swallowed whole, with or without food

Frequency: Once daily for 3 days

Given for 3 days as part of a regimen that includes a corticosteroid and a 5-HT3 antagonist, for the prevention of nausea and vomiting associated with emetogenic cancer chemotherapy. HIGHLY EMETOGENIC CHEMOTHERAPY: aprepitant 125 mg orally Day 1, 80 mg orally Day 2, 80 mg orally Day 3, none Day 4. MODERATELY EMETOGENIC CHEMOTHERAPY: aprepitant 125 mg orally Day 1, 80 mg orally Days 2 and 3. CO-ADMINISTERED AGENTS IN THE SPC REGIMEN (these are not aprepitant doses; the dexamethasone dose stated accounts for the active-substance interaction): highly emetogenic - dexamethasone 12 mg orally Day 1 then 8 mg orally Days 2 to 4, given 30 minutes before chemotherapy on Day 1 and in the morning on Days 2 to 4; moderately emetogenic - dexamethasone 12 mg orally Day 1 only, 30 minutes before chemotherapy; plus the standard dose of the selected 5-HT3 antagonist on Day 1 (refer to that product's SmPC). Efficacy data in combination with other corticosteroids and 5-HT3 antagonists are limited. PAEDIATRIC (not per kg, so not carried in paedDose): adolescents aged 12 through 17 years - 125 mg orally on Day 1 and 80 mg orally on Days 2 and 3, given 1 hour prior to chemotherapy on Days 1, 2 and 3 (or in the morning if no chemotherapy is given on Days 2 and 3), as part of a regimen that includes a 5-HT3 antagonist; if a corticosteroid such as dexamethasone is co-administered, give 50% of the usual corticosteroid dose. Safety and efficacy of the 80 mg and 125 mg capsules have not been demonstrated in children less than 12 years of age (no data). Verify all paediatric use against a children's formulary. Elderly (65 years and over) and gender: no dose adjustment necessary. Hepatic impairment: no adjustment in mild impairment; limited data in moderate and no data in severe impairment - use with caution.

Dose adjustments

Renal

No dose adjustment is necessary for patients with renal impairment or for patients with 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 (common)
Alanine aminotransferase (ALT) increased
Dyspepsia and constipation (common)
Headache (common); dizziness and somnolence (uncommon)
Decreased appetite (common); fatigue

Interactions

Aprepitant (125 mg/80 mg) is a substrate, a moderate inhibitor and an inducer of CYP3A4, and an inducer of CYP2C9; as a moderate CYP3A4 inhibitor it can increase plasma concentrations of co-administered CYP3A4 substrates (total exposure of orally administered CYP3A4 substrates may increase up to approximately 3-fold during the 3-day treatment)
Must not be used concurrently with pimozide, terfenadine, astemizole or cisapride
Use with caution with orally administered CYP3A4 substrates of narrow therapeutic range - ciclosporin, tacrolimus, sirolimus, everolimus, alfentanil, ergot alkaloid derivatives, fentanyl and quinidine; concomitant irinotecan should be approached with particular caution as the combination might result in increased toxicity
Warfarin (a CYP2C9 substrate): monitor INR closely during treatment and for 14 days following each 3-day course
Hormonal contraceptives: efficacy may be reduced during and for 28 days after administration - use alternative non-hormonal back-up contraception during treatment and for 2 months following the last dose
NOTE: the source capture of SPC section 4.5 is truncated; the full interaction section must be checked against the SPC

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 CINV Guidelines 2016; Scuderi PF (PONV aprepitant trial); 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