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Ondansetron information from DrugsUpdate  

See Available Brands of Ondansetron in India

P - Caution when used during pregnancy
L - Caution when used during lactation
FI - Food *

Ondansetron or GlaxoSmithKline's Zofran is a serotonin 5-HT3 receptor antagonist used mainly as an antiemetic to treat nausea and vomiting following chemotherapy. Its effects are thought to be on both peripheral and central nerves. Ondansetron reduces the activity of the vagus nerve, which activates the vomiting center in the medulla oblongata, and also blocks serotonin receptors in the chemoreceptor trigger zone. It has little effect on vomiting caused by motion sickness, and does not have any effect on dopamine receptors or muscarinic receptors.

Pharmacodynamics

Ondansetron is a selective 5-HT3 receptor antagonist. While its mechanism of action has not been fully characterized, Ondansetron is not a dopamine-receptor antagonist. Serotonin receptors of the 5-HT3 type are present both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema. It is not certain whether Ondansetron's antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine. In humans, urinary 5-HIAA (5-hydroxyindoleacetic acid) excretion increases after cisplatin administration in parallel with the onset of emesis. The released serotonin may stimulate the vagal afferents through the 5-HT3 receptors and initiate the vomiting reflex.

Pharmacokinetics

Ondansetron antagonises 5-HT3 receptor, blocking serotonin, both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone.

Onset
Approx 30 minutes.

Absorption

Peak plasma concentrations: Oral: 1.5 hours; rectal: 6 hours.

Distribution

Extensively distributed. Protein-binding: 70-75%.

Metabolism

Hepatic via multiple enzymatic pathways.

Excretion

Via urine (44-60% as metabolites, 5-10% as unchanged), faeces (approx 25%). Terminal elimination half-life: Oral/parenteral: 3 hours; rectal: 6 hours; elderly/renal impairment: prolonged, approx 5 hours; severe hepatic impairment: 15-32 hours.

Ondansetron Indications / Ondansetron Uses

Information Not Available

Ondansetron Adverse Reactions / Ondansetron Side Effects

Headache, malaise/fatigue, constipation; drowsiness, fever, dizziness, anxiety, cold sensation; pruritus, rash; diarrhoea; gynaecological disorder, urinary retention; elevated transaminase; local inj site reaction (pain, redness, burning); paresthesia; hypoxia. Rarely: Anaphylaxis, angina, bronchospasm, ECG changes, extrapyramidal symptoms, grand mal seizure, hypokalaemia, tachycardia, vascular occlusive events.

Precautions

Ondansetron is not a drug that stimulates gastric or intestinal peristalsis. It should not be used instead of nasogastric suction. The use of Ondansetron in patients following abdominal surgery or in patients with chemotherapy-induced nausea and vomiting may mask a progressive ileus and/or gastric distension.

Rarely and predominantly with intravenous Ondansetron, transient ECG changes including QT interval prolongation have been reported.

Overdosage

Sudden transient blindness, severe constipation, hypotension, and vasovagal episode with transient secondary heart block. Treatment is supportive.

Special Precautions

May cause QT prolongation; caution when used in cardiac diseases, patients who are on medications that can prolong QT or patients with electrolyte abnormalities. Severe hepatic impairment. May mask progressive ileus and/or gastric distension. Pregnancy, lactation.

Other Drug Interactions

Rifampicin and other CYP3A4 inducers reduce levels/effects of ondansetron.

Potentially Fatal: Concurrent use may increase the hypotensive effect of apomorphine; avoid concurrent use.

Other Interactions

Food Interaction
Extent of absorption increased with food. St John's wort may reduce serum levels of ondansetron.

Dosage

Oral
Prophylaxis of postoperative nausea and vomiting
Adult: 16 mg taken 1 hour before anaesthesia; or 8 mg taken 1 hour before anaesthesia followed by 2 more doses of 8 mg at 8-hours intervals.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Oral

Nausea and vomiting associated with cancer chemotherapy
Adult: 24 mg, as a single dose, 30 minutes before the start of single-day chemotherapy.
Child: 4-11 years: 4 mg 30 minutes before chemotherapy; repeat dose at 4 and 8 hours after initial dose, then 4 mg every 8 hours for 1-2 days after completion of chemotherapy.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Oral

Nausea and vomiting associated with cancer chemotherapy or radiotherapy
Adult: For less emetogenic chemotherapy and/or radiotherapy: 8 mg 2 hours before treatment followed by 8 mg 8-12 hours later.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Oral
Prevent delayed emesis following chemotherapy
Adult: 8 mg bid, for up to 5 days after the end of a course of chemotherapy.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Parenteral

Nausea and vomiting associated with cancer chemotherapy
Adult: For highly emetogenic chemotherapy: 8 mg as a single dose, given via IM or slow IV injection immediately before treatment; or 8 mg IM or slow IV injection given immediately before treatment followed by either continuous IV infusion of 1 mg/hr for up to 24 hours or by a further 2 doses of 8 mg 2-4 hours apart; or 32 mg as a single dose via IV infusion over ≥15 minutes immediately before treatment; or 150 mcg/kg via IV infusion over 15 minutes (beginning 30 minutes before chemotherapy) and repeated 4 and 8 hours after the 1st dose. Anti-emetic efficacy can be enhanced by giving 20 mg dexamethasone sodium phosphate via IV admin before chemotherapy.
Child: ≥6 months: 150 mcg/kg via IV infusion 30 minutes before the start of chemotherapy, repeat dose at 4 and 8 hours after the first dose; or 0.45 mg/kg/day as a single dose.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Parenteral
Prophylaxis of postoperative nausea and vomiting
Adult: 4 mg as a single dose via IM or slow IV injection at induction of anaesthesia.
Child: ≥1 month: ≤40 kg: 100 mcg/kg as a single dose; >40 kg: 4 mg as a single dose.
Max Dosage: Child: 4 mg.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Parenteral
Postoperative nausea and vomiting
Adult: 4 mg IM or slow IV injection as a single dose.
Child: ≥1 month: 100 mcg/kg slow IV injection, up to a maximum of 4 mg.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Rectal
Nausea and vomiting associated with cancer chemotherapy
Adult: As suppository: 16 mg given 1-2 hours before treatment.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Rectal
Prevent delayed emesis following chemotherapy
Adult: As suppository: 16 mg once daily, for up to 5 days after the end of a course of chemotherapy.
Hepatic impairment: Moderate or severe hepatic impairment: Max: 8 mg daily.

Reconstitution
Prior to IV infusion, dilute in 50 ml D5W or normal saline.

Incompatibility

Y-site incompatibility: Acyclovir, allopurinol, aminophylline, furosemide, ganciclovir, lorazepam, amphotericin B, amphotericin B cholesteryl sulfate complex, ampicillin, ampicillin/sulbactam, piperacillin, sargramostim, sodium bicarbonate, amsacrine, cefepime, cefoperazone, methylprednisolone sodium succinate.

Food(before/after)

May be taken with or without food.

List of Contraindications

Ondansetron and Pregnancy

Caution when used during pregnancy

Category B: Either animal-reproduction studies have not demonstrated a foetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).

Ondansetron and Lactation

Caution when used during lactation

Ondansetron and Children

Information Not Available

Ondansetron and Geriatic

The dosage recommendation is the same as for the general population.

Ondansetron and Other Contraindications

Use with apomorphine (profound hypotension).

Storage

Oral
Oral solution: Store at 15-30 °C. Protect from light.

Tablets
Store at 2-30°C .

Parenteral
Vial: Store at 2-30°C. Protect from light. Stable with D5W or normal saline for 48 hours at room temperature.

Lab interference

Oral
Oral solution: Store at 15-30 °C. Protect from light.

Tablets
Store at 2-30°C .

Parenteral
Vial: Store at 2-30°C. Protect from light. Stable with D5W or normal saline for 48 hours at room temperature.

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