Ondansetron

Oral products prevent nausea/vomiting from highly emetogenic single-day chemotherapy, moderately emetogenic chemotherapy, specified abdominal/total-body radiotherapy and surgery. Injection prevents initial/repeat emetogenic chemotherapy-associated nausea/vomiting in adults and children ≥6 months and postoperative nausea/vomiting in adults and children ≥1 month.

Oral pediatric support is for moderately emetogenic chemotherapy in ages ≥4; other oral pediatric indications are not established. Injection may treat further postoperative episodes when no prophylactic antiemetic was given; routine prophylaxis is not recommended when postoperative risk is low. No gastroenteritis, pregnancy-nausea or other off-label dosing is supplied.

Tablets, ODT and solution use the corresponding oral milligram dose; the selected solution is 4 mg/5 mL. The 24 mg chemotherapy dose below is oral only.

For moderately emetogenic chemotherapy only: ages 12–17 use the adult 8 mg regimen. Ages 4–11 receive 4 mg 30 minutes before chemotherapy, repeated 4 and 8 hours after the first dose, then 4 mg three times daily for 1–2 days after completion. Below 4 years, oral safety/effectiveness is not established.

For chemotherapy in adults/children ≥6 months: 0.15 mg/kg IV per dose, maximum 16 mg per dose, for three doses. Dilute in 50 mL D5W or normal saline; smaller 10–50 mL volumes may be appropriate at age 6–12 months and/or weight ≤10 kg. Infuse each dose over 15 minutes, first starting 30 minutes before chemotherapy, then 4 and 8 hours after the first dose.

• Postoperative dose: immediately before induction, or after surgery if no prophylaxis and nausea/vomiting occurs within 2 hours. No dilution is required for this use.
• An additional adult 4 mg IV dose after prior 4 mg prophylaxis did not improve control. Pediatric postoperative evidence is in patients without prior prophylactic ondansetron.
• The former 32 mg single IV regimen was removed for QT risk; do not use it.

Severe hepatic impairment (Child–Pugh ≥10): maximum total 8 mg/day across routes. The injection chemotherapy label uses one 8 mg infusion over 15 minutes before chemotherapy, with no experience beyond day one. No oral adjustment is required for mild/moderate hepatic impairment. No renal adjustment is recommended, but oral experience beyond the first day in renal impairment is limited. Peel ODT foil with dry hands, place immediately on the tongue, and swallow with saliva; water is unnecessary. Measure solution with an accurate oral device.

Ondansetron/product ingredient hypersensitivity and concurrent apomorphine are contraindications. Apomorphine combination has caused profound hypotension and loss of consciousness.

The selected current oral and injectable labels have no boxed warning. This does not remove QT/torsades, myocardial ischemia, serotonin syndrome or anaphylaxis precautions.

Common reported reactions include headache, constipation, diarrhea and fatigue, with rates varying by indication and co-treatment; injection reactions also occur. Serious reports include arrhythmias, ischemia, hypersensitivity, severe skin reactions and transient visual loss, particularly after IV use. Excess exposure can cause hypotension, conduction effects or serotonin toxicity; no specific antidote is established. Obtain urgent medical/toxicology assessment and supportive monitoring.

Pregnancy observational studies have inconsistent findings concerning oral clefts/cardiac defects and important methodological limitations; they do not establish absence of fetal risk. Balance clinical need and uncertainty. Current labels describe limited postpartum IV data suggesting low milk exposure and no attributed infant adverse effects at doses up to 4 mg/day; effects on milk production are unknown. Repeated/higher oral dosing should not be assumed equivalent.

Oral moderate-chemotherapy use is supported ≥4 years; injection chemotherapy ≥6 months and postoperative use ≥1 month. Closely monitor infants <4 months receiving injection because clearance is slower and half-life is longer. Older adults have reduced clearance; no routine adjustment is recommended, but data above 75 are limited and cardiac risks require review.

Severe hepatic impairment increases exposure and prolongs half-life, requiring the 8 mg/day total limit. No fixed renal adjustment is recommended. Dose/monitoring still depends on route, comorbidity and the limited duration of renal/severe-hepatic study experience.

Ondansetron selectively antagonizes serotonin 5-HT3 receptors; chemotherapy-associated emetic signaling involves peripheral vagal and central pathways. It is not a dopamine antagonist and does not stimulate gastric motility.

Oral absorption

Approximately 56% bioavailability after an 8 mg tablet; first-pass metabolism. Peak concentrations usually ~1.7–2 hours.

Metabolism / binding

CYP3A4, CYP2D6 and CYP1A2; approximately 70–76% protein binding.

Elimination

Extensive metabolism; ~5% unchanged in urine. Adult half-life commonly ~3–6 hours, varying with age/sex/study.

Severe liver impairment

Half-life may approach 20 hours; use the total daily dose restriction.

• Review regimen, route, age/weight and liver disease; reconcile all-route daily exposure.
• Assess cardiac history, interacting medicines and electrolyte risks; obtain ECG monitoring when indicated.
• Follow nausea/vomiting, hydration, bowel activity and postoperative abdominal symptoms.
• Observe infusion-rate tolerance, myocardial ischemia, allergy and serotonin-syndrome symptoms.

• Follow the exact oral/IV schedule; do not substitute oral high-dose regimens for injection.
• Use dry hands and peel ODT foil; use an accurate measuring device for solution.
• Report fainting, palpitations, chest pain, breathing difficulty, swelling or severe rash promptly.
• Tell the care team about apomorphine, serotonergic/QT medicines, liver disease, pregnancy/breastfeeding and phenylketonuria.

Dosage form / strength

Orally disintegrating tablet · 4 mg

Labeler

Glenmark Pharmaceuticals Inc., USA

Appearance / imprint

White, round, flat tablet · G / 4

Example NDC

68462-157-13 · 30 tablets in unit-dose blisters

Selected Glenmark film-coated tablets and ODT: 4 and 8 mg. PAI oral solution: 4 mg/5 mL (0.8 mg/mL). Hikma injection: 2 mg/mL, supplied as 4 mg/2 mL single-dose or 40 mg/20 mL multidose vials. Other products may have different packaging/excipients; verify the label.

Selected products use 20–25°C controlled room temperature. Protect film-coated tablets, oral solution and injection from light; keep solution upright in its carton and ODT in its blister until use. For injection chemotherapy dilution, the label limits use to 24 hours after preparation; inspect the diluted solution and follow sterile preparation instructions. Do not mix with unverified solutions, particularly alkaline preparations.