Antiemetic (5-HT3 receptor antagonist)
5-HT3 receptor antagonist antiemetic indicated for prevention of nausea and vomiting associated with highly and moderately emetogenic cancer chemotherapy, radiotherapy, and postoperative nausea and vomiting.
Also known as: Zofran, Zofren, ondansetron
DailyMed approved label (Ondansetron Hydrochloride Tablet; setID 14276805-4e99-4bbe-ad76-ffc06eddb38a).
DailyMed approved label (Ondansetron Hydrochloride Tablet; setID 14276805-4e99-4bbe-ad76-ffc06eddb38a).
Combining ondansetron with tramadol raises the risk of serotonin syndrome.
The ondansetron label states that serotonin syndrome has been reported with 5-HT3 receptor antagonists, mostly with concomitant use of serotonergic drugs such as tramadol, and that ondansetron may increase patient-controlled administration of tramadol, so analgesia should be monitored; the tramadol label includes 5-HT3 receptor antagonists among the serotonergic drugs with a risk of serotonin syndrome. Monitor for serotonin symptoms (agitation, tachycardia, hyperthermia, hyperreflexia) and ensure adequate analgesia; use the lowest effective doses.
Ondansetron + tramadol: risk of serotonin syndrome (5-HT3 antagonist + serotonergic drug) and possible increased tramadol use. Monitor analgesia and serotonin.
Tramadol is serotonergic and ondansetron, although a 5-HT3 antagonist, may contribute to serotonergic excess in susceptible patients.
Monitor agitation, tremor, hyperthermia, myoclonus and diarrhoea.
Serotonin syndrome (hyperthermia, rigidity, confusion).
Monitor serotonergic symptoms; use with caution in polypharmacy patients.
DailyMed (FDA) — approved Ondansetron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41366a20-0727-0446-e063-6294a90a957f ; approved Tramadol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9f0e33bd-65f8-446a-886f-e7e16a142ce5 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Alcohol may increase the drowsiness and dizziness associated with ondansetron.
Limit alcohol intake during treatment.
DailyMed/FDA (NIH/NLM) — approved Ondansetron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=14276805-4e99-4bbe-ad76-ffc06eddb38a
Ondansetron can be taken with or without food, with no relevant food interaction.
May be taken with or without food, consistently.
DailyMed/FDA (NIH/NLM) — approved Ondansetron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=14276805-4e99-4bbe-ad76-ffc06eddb38a
Ondansetron is hepatically metabolised; clearance is reduced in moderate to severe hepatic impairment.
Limit the maximum daily dose in hepatic impairment.
EMC-UK (MHRA) — approved Ondansetron SmPC: https://www.medicines.org.uk/emc/product/5222/smpc
Ondansetron may prolong the QT interval, especially at high doses.
Use with caution; avoid doses > 16 mg and combinations with other QT drugs.
EMC-UK (MHRA) — approved Ondansetron SmPC: https://www.medicines.org.uk/emc/product/5222/smpc
Ondansetron is used in hyperemesis gravidarum; evidence on malformations is limited and does not show a clear risk.
Use only if first-line antiemetics are insufficient, preferably in the 2nd/3rd trimester.
Excreted into breast milk in small amounts; probably compatible.
No specific additional contraception.
EMC-UK (MHRA) — approved Ondansetron SmPC: https://www.medicines.org.uk/emc/product/5222/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Selective 5-HT3 receptor antagonist, with receptors present peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema; blocks the vomiting reflex triggered by serotonin released from enterochromaffin cells after chemotherapy or radiotherapy.
Selective blockade of 5-HT3 receptors (not a dopamine receptor antagonist), inhibiting vagal afferent stimulation and the central vomiting trigger.
Mean oral bioavailability of ~56% (8 mg tablet), with some first-pass effect; bioavailability slightly enhanced by food. Plasma protein binding 70–76%.
Extensively metabolized in the liver: hydroxylation of the indole ring followed by glucuronide or sulfate conjugation; substrate of CYP1A2, CYP2D6 and CYP3A4 (CYP3A4 predominant in overall turnover). ~5% of the dose is recovered unchanged in urine.
Mean half-life of ~5.7 h in healthy subjects; increased to ~11.6 h in mild-to-moderate hepatic impairment and ~20 h in severe impairment.
