5-HT3 antagonist antiemetic Pregnancy: Limited data in pregnant women; as a precautionary measure, it is preferable to avoid use during pregnancy. Breast-feeding should not be advised during treatment.

Granisetron

Brand names: Kytril, Sancuso (patch)

Granisetron is a 5-HT3 receptor antagonist antiemetic used to prevent and treat nausea and vomiting associated with chemotherapy, radiotherapy and surgery.

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: 1 mg twice a day or 2 mg once a day

Route: Oral

Frequency: Twice a day (1 mg) or once a day (2 mg), for up to one week following radiotherapy or chemotherapy

Max: The maximum dose of granisetron administered orally and/or intravenously over 24 hours should not exceed 9 mg

For prevention/treatment of nausea and vomiting induced by radiotherapy or chemotherapy. The first dose should be administered within one hour before the start of therapy. Dexamethasone has been used concomitantly at doses up to 20 mg once a day orally. Also available as ampoules for intravenous administration. Tablets should be swallowed whole with water. Older people and renal impairment: no special precautions required. Hepatic impairment: no dosage adjustment necessary but use with caution. Paediatric: safety and efficacy of granisetron tablets in children have not yet been established; no data available.

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

Side effects

Headache (very common)
Constipation (very common)
Insomnia (common)
Diarrhoea (common)
Elevated hepatic transaminases (common)
QT prolongation (uncommon); extrapyramidal reactions (uncommon); serotonin syndrome (uncommon)

Interactions

Medicinal products known to prolong QT interval and/or which are arrhythmogenic (may lead to clinical consequences)
Buprenorphine/opioids: increased risk of serotonin syndrome, a potentially life-threatening condition
No interaction indicated with benzodiazepines (lorazepam), neuroleptics (haloperidol) or anti-ulcer medicinal products (cimetidine)

Clinical monograph

How it works

It selectively blocks serotonin 5-HT3 receptors on vagal afferents in the gut and in the chemoreceptor trigger zone, interrupting the emetic reflex triggered by these stimuli.

Prescribing in practice

It can prolong the QT interval, so use with caution in patients with cardiac conduction abnormalities, electrolyte disturbance or who are taking other QT-prolonging medicines.
Constipation and headache are common adverse effects of 5-HT3 antagonists.
It is used for emetogenic chemotherapy, radiotherapy and post-operative nausea and vomiting, often as part of a combination antiemetic strategy.

Monitoring

Correct electrolyte abnormalities and consider ECG monitoring in patients at risk of QT prolongation or significant cardiac disease.

Counselling the patient

Tell your team if you develop a fast or irregular heartbeat, dizziness or fainting.
Constipation and headache can occur; report troublesome or persistent symptoms.

Evidence & guidelines

5-HT3 receptor antagonists are recommended antiemetics for the prevention of chemotherapy- and radiotherapy-induced nausea and vomiting in line with established oncology guidance.

Reference: NICE TA313; ESMO antiemetic guidelines; 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