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Chemotherapy-induced nausea and vomiting
Prevention is set by the emetic risk of the regimen: high risk — four drugs (NK1 antagonist, 5-HT3 antagonist, dexamethasone and olanzapine), moderate risk — a 5-HT3 antagonist and dexamethasone, and low risk — one drug; prevent in advance and do not wait for vomiting.
Why it matters in the exam
Antiemetic prevention is a supportive topic asked in the exam in questions on choosing the regimen by type of chemotherapy, the difference between acute, delayed and anticipatory nausea, and the side effects and interactions of the drugs. Cisplatin and the anthracycline-cyclophosphamide combination are the classic high-risk examples.
Common distractors are giving a 5-HT3 antagonist alone for a high-risk regimen, forgetting delayed nausea that lasts days after treatment, or treating anticipatory nausea with ordinary antiemetics instead of benzodiazepines and behavioural therapy. Remember too that NK1 antagonists inhibit CYP3A4 and raise dexamethasone levels.
Key points
- Prevention is chosen by the risk level of the most emetogenic drug in the regimen, and starts before treatment, because nausea is much easier to prevent than to stop.
- At high risk, such as cisplatin or anthracycline with cyclophosphamide, give four drugs: NK1, 5-HT3, dexamethasone and olanzapine.
- At moderate risk give a 5-HT3 antagonist and dexamethasone, and with carboplatin add an NK1 antagonist as well.
- Acute nausea, within the first day, is mediated mainly by serotonin, and delayed nausea, lasting several days after treatment, is mediated mainly by substance P.
- Anticipatory nausea is treated with a benzodiazepine and behavioural therapy, and breakthrough nausea with a drug of another mechanism.
Summary table
| Risk level | Examples | Prevention |
|---|---|---|
| High | Cisplatin, anthracycline with cyclophosphamide, high-dose cyclophosphamide | NK1 antagonist, 5-HT3 antagonist, dexamethasone and olanzapine |
| Moderate | Carboplatin, oxaliplatin, irinotecan | 5-HT3 antagonist and dexamethasone; with carboplatin AUC of 4 or more add an NK1 antagonist |
| Low and minimal | Taxanes, 5-FU, gemcitabine; vinca alkaloids and many antibodies | Low — one drug; minimal — no routine prevention |
| Acute nausea | Within 24 hours; mediated mainly by serotonin | 5-HT3 antagonists are especially effective |
| Delayed nausea | After 24 hours and for several days; mediated mainly by substance P | NK1 antagonists, dexamethasone and olanzapine |
| Anticipatory and breakthrough nausea | Anticipatory — a conditioned response before treatment; breakthrough — despite prevention | Anticipatory: a benzodiazepine and behavioural therapy; breakthrough: olanzapine or a drug from another class |
| Side effects | 5-HT3 antagonists — constipation, headache and QT prolongation; olanzapine — sedation; dexamethasone — high glucose and insomnia | NK1 antagonists raise dexamethasone and other drug levels through CYP3A4 |
In the full version for subscribers
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Sources
- MASCC/ESMO Antiemetic Guideline, 2023 — Prevention of chemotherapy- and radiotherapy-induced nausea and vomiting
- ASCO Guideline: Antiemetics, 2020, updated 2025 — Recommendations by emetogenic risk
- NCCN Clinical Practice Guidelines in Oncology: Antiemesis, 2026 — Principles of emesis control
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.