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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Nausea and vomiting during cancer treatment

Oncology and palliative care · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
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Vomiting with sepsis, obstruction, pressure or metabolic collapse

Haemodynamic compromise, fever after systemic treatment, severe abdominal distension or pain, peritonism, faeculent or bloody vomit, focal neurological change, reduced consciousness or profound dehydration and electrolyte loss requires emergency diagnosis rather than further oral antiemetics alone.

Action: Use ABCDE care, isolate and treat suspected neutropenic sepsis immediately, obtain intravenous access, blood count, renal and electrolyte tests and cause-directed imaging. Replace fluid and potassium or magnesium safely, decompress suspected obstruction when indicated and use an intravenous, subcutaneous or buccal antiemetic route while oral absorption is unreliable.

Synopsis

Prevent treatment-related emesis from the first cycle, identify acute, delayed, breakthrough, refractory and anticipatory patterns, exclude dangerous competing causes and match antiemetic class, route, schedule and rescue to regimen risk and patient factors.

  • Classify symptoms as acute within 24 hours, delayed after 24 hours, breakthrough despite prophylaxis, refractory in later cycles or anticipatory before treatment.
  • First-line prevention is chosen from the complete regimen’s emetogenic risk, not from the most familiar drug or the severity of symptoms after they begin.
  • Before every cycle, review what was prescribed, what was actually taken, timing, vomiting count, nausea burden, rescue use, constipation, sedation and cycle-specific control.
  • Highly emetogenic chemotherapy generally requires prophylaxis with an NK1 antagonist, a 5-HT3 antagonist, dexamethasone and olanzapine before treatment, followed by scheduled delayed cover.
  • Anthracycline–cyclophosphamide and high-risk carboplatin regimens need protocol-specific NK1-containing combination prevention; do not treat them as simple single-agent moderate risk.
  • Moderately emetogenic treatment commonly uses a 5-HT3 antagonist plus dexamethasone, with an NK1 antagonist or olanzapine added according to the exact regimen and individual risk.
  • Low-risk treatment usually needs one prophylactic drug and minimal-risk treatment no routine prophylaxis, while always providing a rescue plan.
  • Give prophylaxis before the anticancer exposure and write the delayed days explicitly; an as-required prescription started after vomiting is not adequate prevention.
  • Breakthrough emesis requires hydration assessment and a medicine from a different mechanism, such as olanzapine, dopamine antagonist or benzodiazepine for a selected anticipatory component.
  • Persistent vomiting makes oral rescue unreliable; change to intravenous, subcutaneous, buccal or rectal delivery where appropriate and reassess the diagnosis.
  • Ondansetron is effective but can cause constipation and QT prolongation; correct potassium and magnesium and review other QT-risk drugs.
  • Aprepitant inhibits CYP3A4 and requires a reduced dexamethasone dose in standard antiemetic protocols plus review of warfarin, contraception and other interactions.
  • Olanzapine improves nausea as well as vomiting but causes sedation, postural effects, glucose disturbance and anticholinergic burden; use a lower dose in frailty when protocol permits.
  • Anticipatory nausea is best prevented by excellent first-cycle control; behavioural desensitisation, relaxation and selected short-acting benzodiazepine support later cycles.

Key red flags

Fever, rigors, hypotension, confusion or new oxygen requirement after systemic anticancer treatment is neutropenic sepsis until treated immediately.

Colicky pain, abdominal distension, obstipation, faeculent vomiting or peritonism suggests malignant obstruction, ischaemia or perforation and needs urgent CT and surgical or acute-oncology review.

Progressive headache, focal deficit, seizure, papilloedema or falling consciousness can reflect brain metastasis, haemorrhage or raised intracranial pressure and needs emergency imaging.

Persistent vomiting with oliguria, postural hypotension, acute kidney injury, severe potassium or magnesium loss or QT prolongation requires monitored intravenous correction.

Haematemesis, coffee-ground vomit, melaena or falling haemoglobin requires an upper-gastrointestinal-bleeding pathway rather than routine chemotherapy antiemesis.

Severe headache, agitation, clonus, hyperreflexia and fever during serotonergic combinations raises serotonin toxicity and requires immediate medicine review.

Vomiting after immunotherapy may accompany adrenal crisis, hypophysitis, hepatitis, pancreatitis, colitis or neurological toxicity and needs organ-specific emergency assessment.

Investigation priorities

01
First-line structured symptom and regimen reviewFirst stepFirst line

Classify timing, severity, emetogenic risk, actual prophylaxis, adherence, rescue use, bowel pattern and individual susceptibility.

Management branches

Before treatmentBuild prophylaxis from emetogenic risk

A systemic or radiation treatment course with potential emesis is prescribed.

  1. Classify the complete regimen and radiation field, then add age, sex, alcohol history, motion sickness, pregnancy sickness, anxiety and previous-cycle control.
  2. Prescribe the protocol combination before exposure with exact delayed-day doses, rescue from a different class and constipation, sedation and interaction counselling.
  3. Confirm dispensing and patient understanding before the first dose and arrange a 24-hour contact route and next-cycle review using an individual symptom record.

Key medicines

OndansetronFor moderately emetogenic chemotherapy, a licensed oral schedule is 8 mg one to two hours before treatment, 8 mg twelve hours later, then 8 mg twice daily for up to five days; follow the regimen-specific protocol.Moderate or severe hepatic impairment limits total daily dose to 8 mg; monitor QT and electrolyte risk, constipation or ileus and serotonergic combinations and avoid duplicating the same mechanism for breakthrough treatment.
AprepitantGive aprepitant 125 mg orally one hour before chemotherapy on day 1, then 80 mg once daily on days 2 and 3 as part of the licensed combination regimen.CYP3A4 inhibition requires protocol dexamethasone reduction and interaction review; counsel about reduced hormonal-contraceptive efficacy and monitor warfarin, immunosuppressant and other narrow-therapeutic-index exposure.
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • MASCC and ESMO emesis prevention updateRisk classification and acute, delayed, breakthrough and high-risk combination prophylaxis.
  • Ondansetron Summary of Product CharacteristicsLicensed chemotherapy schedule, hepatic limit, QT and safety information.
  • EMEND Summary of Product CharacteristicsAprepitant three-day schedule, combination use, interactions and contraception.
  • UKONS acute oncology initial management guidelinesAcute assessment, hydration and dangerous alternative-cause pathways.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
Dehydration and electrolyte loss

Postural dizziness, tachycardia, dry mouth, oliguria, weakness or arrhythmia requires urgent renal, potassium and magnesium assessment and replacement.