Ondansetron

Description

Ondansetron is one of the medications most commonly used for the empiric treatment of nausea and vomiting, and it is effective against nausea and vomiting of various etiologies. However, it is not effective for motion sickness-induced nausea.

Indications

• prevention of chemotherapy-induced and radiation-induced nausea
• prevention of post-operative nausea
• treatment of nausea from various other causes

Administration Routes

• Oral
• Intravenous (IV)
• Intramuscular (IV)

Side Effects

• prolongation of QT interval resulting in arrhythmias
• constipation
• headache
• dry mouth
• malaise
• drowsiness or sedation
• itchiness

Dosage

For prevention of post-operative nausea:

• 65 μg/kg IV/IM immediately before anesthesia or after procedure
• or, 200 μg/kg oral 1 hour before anesthesia

Prophylaxis for moderate chemotherapy nausea:

• 100 μg/kg oral given 30 minutes before chemotherapy, then every 12 hours for 1-2 days after

Prophylaxis for severe chemotherapy nausea:

• 300 μg/kg oral given 30 minutes before chemotherapy
• or, 150 μg/kg IV over 15 min administered 30 min before chemotherapy, then again at 4 and 8 hours after first dose. further doses increase risk of arrhythmia.

Prophylaxis for total body radiation therapy:

• 200 μg/kg oral 1-2 hours before radiation therapy; administered each day

Prophylaxis for single high-dose fraction radiation therapy to abdomen:

• 200 μg/kg oral 1-2 hours before radiation therapy
• administer subsequent doses every 8 hr after first dose for 1-2 days after completion of therapy

Prophylaxis for daily fractions to abdomen:

• 200 μg/kg oral 1-2 hours before radiotherapy
• administer subsequent doses every 8 hours after first dose each day radiotherapy is given

Available forms

• 1 mg tablet

• 2 mg tablet

• 4 mg tablet

• 0.5 mg/mL oral solution

• 0.5 mg/mL injectable solution

• 1 mg/mL injectable solution

• 2.5 mg / 5 mL prefilled syringe (0.5 mg/mL)

Pharmacokinetics

Route	Onset	Peak	Elimination Half-life	Duration of action
IV	5 mins	30 mins	3-4 hours	4-8 hours
IM	15 mins
O	30 mins	90-120 mins

Oral bioavailability: 60% without food, 75% with food

Interactions

TODO