Ondansetron (Perioperative)

Source: UK SPC (eMC) §4.2 for Ondansetron 2 mg/ml Solution for Injection (https://www.medicines.org.uk/emc/product/6469/smpc). VERBATIM (PONV prevention, adults): 'Ondansetron may be administered as a single dose of 4 mg given by slow intravenous injection at induction of anaesthesia.' VERBATIM (treatment of established PONV): 'For treatment of established PONV a single dose of 4 mg given by slow intravenous injection is recommended.' The SPC notes that for prevention of PONV ondansetron can also be administered by other dosage forms, but this product is for intravenous use only. SEPARATE INDICATION — CHEMOTHERAPY/RADIOTHERAPY-INDUCED NAUSEA AND VOMITING (adults), included for completeness, NOT the perioperative regimen: emetogenic chemotherapy or radiotherapy — 8 mg as a slow IV injection (in not less than 30 seconds) or as an infusion over 15 minutes immediately before treatment, followed by non-intravenous dosage forms to protect against delayed or prolonged emesis after the first 24 hours. Highly emetogenic chemotherapy — equally effective IV schedules over the first 24 hours are (a) a single 8 mg dose by slow IV injection immediately before chemotherapy; (b) 8 mg by slow IV injection or short 15-minute infusion immediately before chemotherapy followed by two further IV doses of 8 mg four hours apart, or by a constant infusion of 1 mg/hour for up to 24 hours; (c) a maximum initial IV dose of 16 mg diluted in 50–100 ml of sodium chloride 0.9% or other compatible fluid and infused over not less than 15 minutes immediately before chemotherapy, optionally followed by two additional 8 mg IV doses four hours apart. Efficacy in highly emetogenic chemotherapy may be enhanced by adding a single IV dose of dexamethasone sodium phosphate 20 mg before chemotherapy. ELDERLY: in patients 65 to 74 years the adult dose schedule can be followed, with all IV doses diluted in 50–100 ml of saline or other compatible fluid and infused over 15 minutes; in patients 75 years or older the initial IV dose should not exceed 8 mg, diluted and infused over 15 minutes, and may be followed by two further IV doses of 8 mg infused over 15 minutes and given no less than four hours apart. There is limited experience of ondansetron in the prevention and treatment of PONV in the elderly. HEPATIC IMPAIRMENT: clearance is significantly reduced and serum half-life significantly prolonged in moderate or severe impairment — a total daily dose of 8 mg should not be exceeded. POOR SPARTEINE/DEBRISOQUINE METABOLISERS: no alteration of daily dosage or frequency of dosing is required. §4.5 was not present in the fetched bundle — the interaction listed is the one named within §4.3.

PONV in children aged 1 month and over, and adolescents. VERBATIM (§4.2): 'For prevention of PONV in paediatric patients having surgery performed under general anaesthesia, a single dose of ondansetron may be administered by slow intravenous injection (not less than 30 seconds) at a dose of 0.1 mg/kg up to a maximum of 4 mg either prior to, at or after induction of anaesthesia.' The same 0.1 mg/kg up to a maximum of 4 mg applies to the treatment of PONV after surgery and to treatment of established PONV. 'There are no data on the use of ondansetron in the treatment of PONV in children below 2 years of age.' SEPARATE INDICATION — CINV in children aged 6 months and over and adolescents (NOT the perioperative dose): by body surface area, a single IV dose of 5 mg/m2 immediately before chemotherapy, with the IV dose not exceeding 8 mg; or by bodyweight, a single IV dose of 0.15 mg/kg immediately before chemotherapy with the IV dose not exceeding 8 mg, and up to two further IV doses at 4-hourly intervals. Total daily dose must not exceed the adult dose of 32 mg. Weight-based dosing results in higher total daily doses than BSA-based dosing. For CINV the injection should be diluted in 5% glucose or 0.9% sodium chloride or other compatible infusion fluid and infused over not less than 15 minutes.