Drug information of Ondansetron

Ondansetron

Drug group: Antiemetic

Ondansetron blocks the actions of chemicals in the body that can trigger nausea and vomiting .
Ondansetron is used to prevent nausea and vomiting that may be caused by surgery, cancer chemotherapy, or radiation treatment.
A competitive serotonin type 3 receptor antagonist. It is effective in the treatment of nausea and vomiting caused by cytotoxic chemotherapy drugs, including cisplatin, and has reported anxiolytic and neuroleptic properties.

Mechanism of effect

Ondansetron is a selective serotonin 5-HT3 receptor antagonist. The antiemetic activity of the drug is brought about through the inhibition of 5-HT3 receptors present both centrally (medullary chemoreceptor zone) and peripherally (GI tract).
This inhibition of 5-HT3 receptors in turn inhibits the visceral afferent stimulation of the vomiting center, likely indirectly at the level of the area postrema, as well as through direct inhibition of serotonin activity within the area postrema and the chemoreceptor trigger zone.

Pharmacodynamic

Ondansetron is a highly specific and selective serotonin 5-HT3 receptor antagonist, not shown to have activity at other known serotonin receptors and with low affinity for dopamine receptors.
The serontonin 5-HT3 receptors are located on the nerve terminals of the vagus in the periphery, and centrally in the chemoreceptor trigger zone of the area postrema.
The serotonin then stimulates the vagal and splanchnic nerve receptors that project to the medullary vomiting center, as well as the 5-HT3 receptors in the area postrema, thus initiating the vomiting reflex, causing nausea and vomiting.

Pharmacokinetics

Absorption
• Bioavailability: 56-71% (PO); food increases extent of absorption (17%)
• Onset: 30 min
• Peak plasma time: IV, end of infusion; IM, 30 min; PO, 2 hr (tablet) or 1 hr (soluble film)
Distribution
• Protein bound: 70-76%
• Vd: Children, 1.7-3.7 L/kg; adults, 2.2-2.5 L/kg
Metabolism
• Extensive hepatic metabolism, with hydroxylation followed by glucuronide (indole ring) or sulfate conjugation; metabolized by CYP2D6 and partly by CYP1A2 and CYP3A4
• Metabolites: Glucuronide conjugate, sulfate conjugate (inactive)
Elimination
• Half-life: 2-7 hr (children <15 years); 3-7 hr (adults); patients with mild to moderate hepatic impairment, 12 hr; patients with severe hepatic impairment (Child-Pugh class C), 20 hr
• Renal Clearance: 0.26-0.38 L/hr/kg
• Total body clearance: 600-700 mL/min
• Excretion: Primarily urine (30-70%); feces (25%)

Dosage

Take ondansetron exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended .
Ondansetron can be taken with or without food.
The first dose is usually taken before the start of your surgery, chemotherapy, or radiation treatment. Follow your doctor's dosing instructions very carefully.
Take the ondansetron regular tablet with a full glass of water.
Dosage injectable solution : 2mg/mL
tablet: 4mg/ 8mg / 24mg
oral solution : 4mg/5mL
oral soluble film : 4mg /8mg
orally disintegrating tablets : 4mg /8mg
adult :
Chemotherapy-Induced Nausea & Vomiting
Prophylaxis
PO
• Moderately emetogenic chemotherapy: 8 mg started 30 minutes before chemotherapy, then q12hr for 1-2 days after chemotherapy
• Highly emetogenic chemotherapy: 24 mg started 30 minutes before chemotherapy
IV
• 0.15 mg/kg over 15 min administered 30 min before chemotherapy, then 4 and 8 hr after first dose; not to exceed 16 mg (32 mg no longer recommended because of increased risk of QT prolongation)
Postoperative Nausea & Vomiting
Prophylaxis
4 mg IV/IM immediately before anesthesia or after procedure or 16 mg PO 1 hr before anesthesia; patients >80 kg may need additional 4 mg IV
Radiation-Induced Nausea & Vomiting
Prophylaxis
Total body radiation therapy: 8 mg PO 1-2 hours before radiation therapy; administered each day
Dosage Modifications
Renal impairment: Dose adjustment not necessary
Severe hepatic impairment (Child-Pugh score ≥10): Not to exceed 8 mg/day
Pediatric:
Chemotherapy-Induced Nausea & Vomiting
Prophylaxis
PO
• <4 years old: Safety and efficacy not established
• 4-12 years: 4 mg started 30 min before chemotherapy, then 4 and 8 hr after first dose, then q8hr for 1-2 days after chemotherapy .
• >12 years: 8 mg started 30 min before chemotherapy, then q12hr for 1-2 days after chemotherapy, or single dose of 24 mg
IV
• <6 months: Safety and efficacy not established
• ≥6 months: 0.15 mg/kg over 15 min administered 30 min before chemotherapy, then repeated 4 and 8 hr after first dose; not to exceed 16 mg/dose (32 mg no longer recommended because of increased risk of QT prolongation)
Postoperative Nausea & Vomiting
Prophylaxis
1 month-12 years
• <40 kg, 0.1 mg/kg IV
• >40 kg, 4 mg IV
>12 years
• 4 mg IV/IM immediately before anesthesia or after procedure or 16 mg PO 1 hr before anesthesia; patients >80 kg may need additional 4 mg IV

Alerts

You should not use ondansetron if :
• you are also using apomorphine (Apokyn); or
• you are allergic to ondansetron or similar medicines (dolasetron, granisetron, palonosetron).
To make sure ondansetron is safe for you, tell your doctor if you have :
• liver disease;
• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);
• congestive heart failure, slow heartbeats;
• a personal or family history of long QT syndrome; or
• a blockage in your digestive tract (stomach or intestines).
Ondansetron is not expected to harm an unborn baby. Tell your doctor if you are pregnant.
It is not known whether ondansetron passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
Ondansetron is not approved for use by anyone younger than 4 years old.
Ondansetron orally disintegrating tablets may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU).

Points of recommendation

Take ondansetron exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended .
Ondansetron can be taken with or without food.
The first dose is usually taken before the start of your surgery, chemotherapy, or radiation treatment. Follow your doctor's dosing instructions very carefully.
Take the ondansetron regular tablet with a full glass of water.

Pregnancy level

B


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