Ondansetron
Antiemetic & Gastroprokinetic · 5HT3-antagonist
Indications
Nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy. Prophylaxis and treatment of postoperative nausea, vomiting.
Dosage
Adults: Chemotherapy and radiotherapy: Highly emetogenic regimens: Single dose of 8 mg by slow IV inj immediately prior to chemotherapy; or 8 mg by slow IV inj prior to chemotherapy followed by either two doses of 8 mg by IV inj repeated 2-4 hr apart or by 1 mg per hr by IV infusion for up to 24 hr; or single dose of 32 mg in 50-100 mL saline infused over 15 min prior to chemotherapy. After first 24 hrs, follow by 8 mg orally twice daily for up to 5 days. Efficacy may be enhanced by addition of dexamethasone 20 mg IV prior to chemotherapy. Less emetogenic regimens: 8 mg by slow IV inj immediately prior to chemotherapy, or orally 1-2 hr before, followed by 8 mg orally twelve hrly. After first 24 hrs, follow by 8 mg orally twice daily for up to 5 days. Prophylaxis of post-operative nausea and vomiting: 8 mg orally 1 hr prior to anaesthesia followed by two doses of 8 mg orally at 8 hrly…
Administration
IM: Should be given undiluted. IV: Give first dose 30 min prior to beginning chemotherapy; the IV preparation has been successful when administered orally. IVPB: Infuse over 15-30 min; 24-hour continuous infusions have been reported, but are rarely used. Reconstitution: Prior to IV infusion, dilute in 50-100 mL D5W or NS. Compatibility: Stable in D5 ½ NS, D5NS, D5W, mannitol 10%, LR, NS, NS 3%. Do not mix injection with alkaline solutions. Y-site administration: Drug to Drug IV Compatibility: Amikacin, azithromycin, aztreonam, bumetanide, calcium gluconate, cephazolin, cimetidine, ciprofloxacin, cisatracurium, dexamethasone, diltiazem, diphenhydramine, dobutamine, dopamine, enalapril, epinephrine, esmolol, famotidine, fentanyl, fluconazole, gentamicin, heparin, hydrocortisone, hydromorphone, imipenem, labetalol, levofloxacin, linezolid, magnesium sulphate, metoclopramide, midazolam,…
Adverse Effects
Constipation, headache, flushing. Transient rise in liver enzymes. Rarely hypersensitivity reactions, anaphylaxis, chest pain, ST segment depression, cardiac arrhythmia, hypotension, bradycardia, extrapyramidal reactions, seizures, visual disturbance.
Risk Factor (Pregnancy/Lactation)
Pregnancy: No evidence of risk in humans. Lactation: Caution advised or effect undetermined. Contraindications: Congenital long QT syndrome. Precautions: Hepatic impairment, intestinal obstruction. Risk factors for arrhythmias. Correct electrolyte disturbances before starting treatment. Adenotonsillar surgery.
Interactions
Phenytoin, rifampicin, carbamazepine, tramadol, apomorphine, serotonergic drugs (SSRIs, SNRIs), hepatotoxic drugs. Drugs that prolong QT interval, increase risk of arrhythmia (e.g., anthracyclines, B blockers, amiodarone, erythromycin, ketoconazole) or cause electrolyte abnormalities.
Advice to Patient
Take oral forms with or without meals. Use calibrated container or oral syringe to measure oral solution. Orally disintegrating tablets: Do not remove from blister until needed. Peel backing off the blister, do not push tablet through. Using dry hands, place disintegrating tablet on tongue immediately after opening package and let it dissolve on tongue before swallowing. Swallow with saliva. Contact prescriber if there is constant headache, excessive drowsiness, fever, numbness or tingling, constipation, diarrhoea, chest pain or palpitations. Change position slowly.
Pharmacokinetics
Onset of action: Approx. 30 min. Absorption: Oral: 100%. Metabolism: Extensively hepatic. Bioavailability: Oral: 50%-70%. Cancer patients: 85%-87%. Half-life elimination: Children: Cancer patients: 4-18 yrs: 2.8 hrs. Surgical patients: Infants 1-4 mth: 6.7 hrs. 5 mth-12 yrs: 2.9 hrs. Adults: 3-6 hrs. Mild-to-moderate hepatic impairment (Child-Pugh classes A and B): 12 hrs. Severe hepatic impairment (Child-Pugh class C): 20 hrs. Time to peak: Oral: Approx. 2 hrs. Oral soluble film: Approx. 1 hr. Excretion: Urine, faeces.
Brands with this active ingredient
Compiled by Healify Pharmacy from published drug references. How we compile it →
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