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All about: Ondansetron Hydrochloride

Big Image Pronouncation: (ahn-DAN-SEH-trahn HIGH-droe-KLOR-ide)
Class: 5-HT 3 receptor antagonist

Trade Names:
- Tablets 4 mg (as HCl dihydrate)
- Tablets 8 mg (as HCl dihydrate)
- Tablets 24 mg (as HCl dihydrate)
- Solution, oral 4 mg/5 mL (5 mg as HCl dihydrate)
- Injection 2 mg/mL (as HCl dihydrate)
- Injection 32 mg/50 mL (as HCl dihydrate)

Trade Names:
Zofran ODT
- Tablets, orally-disintegrating 4 mg (as base)
- Tablets, orally-disintegrating 8 mg (as base)

Mechanism of Action


Selective serotonin (5-HT 3 ) receptor antagonist that inhibits serotonin receptors in GI tract or chemoreceptor trigger zone.



Passively and completely absorbed from GI tract. Bioavailability is 48% to 75% and is slightly enhanced with food.

C max for males is 24.1 to 37 ng/mL (8 mg oral dose). C max for females is 42.7 to 52.4 ng/mL (8 mg oral dose). C max for injection is 102 to 170 ng/mL. T max for males is 2 to 4.1 hr (8 mg dose). T max for females is 1.7 to 4.9 hr (8 mg dose).


Plasma protein binding is 70% to 76%.


Extensively metabolized in the liver by hydroxylation, followed by glucuronide or sulfate conjugation; CYP1A2, CYP2D6, CYP3A4 are the main hepatic enzymes.


Approximately 5% is eliminated as parent compound in urine. The t ½ for males is 2.1 to 4.5 hr (8 mg oral dose). The t ½ for females is 1.9 to 6.2 hr (8 mg dose). The t ½ for injection is 3.5 to 5.5 hr. Plasma clearance is 0.262 to 0.381 L/hr/kg.

Special Populations


In elderly over 75 yr, there is a reduction in clearance and an increase in elimination half-life. No dosage adjustment is necessary.


The extent and rate of absorption is greater in women than in men. There is slower clearance, a smaller volume of distribution, and higher bioavailability in women.

Severe Hepatic Insufficiency

Clearance is reduced 2- to 3-fold. The volume of distribution is increased. The half-life is increased to 20 hr. Bioavailability approaches 100%. A total daily dose of 8 mg should not be exceeded.

Severe Renal Insufficiency

There is a reduction in clearance. Oral plasma clearance was reduced by 50%. No dosage adjustment is necessary.

Indications and Usage

Parenteral and oral

Prevention of nausea and vomiting with initial and repeat courses of emetogenic cancer chemotherapy, including high-dose cisplatin; prevention of postoperative nausea or vomiting.


Prevention of nausea and vomiting associated with radiotherapy in patients receiving either total body irradiation, single high-dose fraction to the abdomen, or daily fractions to the abdomen; prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy, including cisplatin 50 mg/m 2 or more.

Unlabeled Uses

Treatment of nausea and vomiting associated with acetaminophen poisoning or prostacyclin therapy; treatment of acute levodopa-induced psychosis (visual hallucinations); reduction in bulimic episodes due to bulimia nervosa; treatment of spinal or epidural morphine-induced pruritus; management of social anxiety disorder.


Standard considerations.

Dosage and Administration

Prevention of Chemotherapy-Induced Nausea and Vomiting

IV 0.15 mg/kg infused over 15 min beginning 30 min before emetogenic chemotherapy with 2 additional 0.15 mg/kg doses 4 and 8 hr after the first dose. Alternatively, infuse 32 mg over 15 min, starting 30 min prior to emetogenic chemotherapy.

Adults and children 12 yr and older

PO (moderately emetogenic cancer chemotherapy) 8 mg bid, administering the first dose 30 min prior to starting emetogenic chemotherapy and the second dose 8 hr after the first dose; subsequent 8 mg doses may be given q 12 hr for 1 to 2 days after completion of chemotherapy.

Children 4 to 11 yr

PO 4 mg tid, starting 30 min prior to chemotherapy, with subsequent doses 4 and 8 hr after the first dose; give 4 mg q 8 hr for 1 to 2 days after completion of chemotherapy.

Prevention of Radiotherapy-Induced Nausea and Vomiting

PO 8 mg tid.

Total Body Irradiation

PO 8 mg 1 to 2 hr prior to each fraction of radiotherapy administered each day.

Single High-Dose Fraction Radiotherapy to the Abdomen

PO 8 mg 1 to 2 hr prior to radiotherapy, with subsequent doses q 8 hr after the first dose for 1 to 2 days after completion of radiotherapy.

Daily Fractionated Radiotherapy to the Abdomen

PO 8 mg 1 to 2 hr prior to radiotherapy, with subsequent doses q 8 hr after the first dose for each day radiotherapy is given.

Prevention of Postoperative Nausea and Vomiting

IV 4 mg (undiluted) over 30 sec (preferably over 2 to 5 min) or IM 4 mg (undiluted) as a single injection. PO 16 mg as a single dose 1 hr prior to induction of anesthesia.

Children (2 to 12 yr weighing 40 kg or less)

IV 0.1 mg/kg

Children (more than 40 kg)

IV 4 mg single dose. Administer over 30 sec or longer, preferably over 2 to 5 min.

Prevention of Nausea and Vomiting due to Highly Emetogenic Cancer Chemotherapy

PO 24 mg given 30 min prior to start of single-day highly emetogenic chemotherapy, including 50 mg/m 2 or more cisplatin.

Drug Interactions

Rifamycins (eg, rifampin)

Plasma levels of ondansetron may be reduced, decreasing the antiemetic effect.


Alkaline solutions.

Laboratory Test Interactions

None well documented.

Adverse Reactions


Chest pain; tachycardia.


Headache; seizures.




Dry mouth; constipation; abdominal pain.






Fever; anaphylaxis; weakness.



Category B .




Dosing in children younger than 4 yr is not well defined.

Hepatic Function

In patients with severe hepatic impairment, do not exceed 8 mg/day oral dose. For IV use, give single 8 mg/day dose over 15 min beginning 30 min before chemotherapy.


Ondansetron does not stimulate gastric or intestinal peristalsis; may mask progressive ileus or gastric distention.



Hypotension, constipation.

Patient Information

  • Advise patient that headache is a common side effect.
  • Advise patient that medication will greatly reduce likelihood of nausea and vomiting, but that these are still possible.

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