Ondansetron; Uses, Dosage, Side Effects, Interactions, Pregnancy

Ondansetron
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Ondansetron is 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.

Ondansetron is a carbazole derivative with antiemetic activity. As a selective serotonin receptor antagonist, ondansetron competitively blocks the action of serotonin at 5HT3 receptors, resulting in suppression of chemotherapy- and radiotherapy-induced nausea and vomiting.

 

Ondansetron is a well-tolerated drug with few side effects. A headache, constipation, and dizziness are the most commonly reported side effects associated with its use. There have been no significant drug interactions reported with this drug’s use. It is broken down by the hepatic cytochrome P450 system and it has little effect on the metabolism of other drugs broken down by this system; Ondansetron is a serotonin 5-HT3 receptor antagonist used mainly to treat nausea and vomiting following chemotherapy. Its effects are thought to be on both peripheral and central nerves. One part is to reduce the activity of the vagus nerve, which is a nerve that activates the vomiting center in the medulla oblongata, the other is a blockage of serotonin receptors in the chemoreceptor trigger zone. It does not have much effect on vomiting due to motion sickness. This drug does not have any effect on dopamine receptors or muscarinic receptors; A competitive serotonin types 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; Ondansetron (INN) is a serotonin 5-HT3 receptor antagonist used mainly to treat nausea and vomiting following chemotherapy. Its effects are thought to be on both peripheral and central nerves. One part is to reduce the activity of the vagus nerve, which is a nerve that activates the vomiting center in the medulla oblongata, the other is a blockage of serotonin receptors in the chemoreceptor trigger zone. It does not have much effect on vomiting due to motion sickness. This drug does not have any effect on dopamine receptors or muscarinic receptors.

Mechanism of Action of Ondansetron

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. 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 temporal relationship between the emetogenic action of emetogenic drugs and the release of serotonin, as well as the efficacy of antiemetic agents, suggest that chemotherapeutic agents release serotonin from the enterochromaffin cells of the small intestine by causing degenerative changes in the GI tract. 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.

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Indications of Ondansetron

For the prevention of nausea and vomiting associated with emetogenic cancer chemotherapy, postoperation, and radiation. Also used for the treatment of postoperative nausea and vomiting.

Therapeutic Indications of Ondansetron

Contra Indications of Ondansetron

Dosage of Ondansetron

Strengths: 4 mg, 8 mg, 16 mg ,32 mg,  4 mg/5 mL; 32 mg/50 mL-D5%; 2 mg/mL;

Chemotherapy Induced Nausea/Vomiting 

Highly Emetogenic Cancer Chemotherapy (HEC)

  • Recommended dose: 24 mg orally 30 minutes before the start of single-day HEC (including cisplatin doses of 50 mg/m2 or greater)

Moderately Emetogenic Cancer Chemotherapy (MEC)

  • Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral

  • Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy and subsequent doses given 4 and 8 hours after the first dose.
  • Maximum dose: 16 mg per dose

Nausea/Vomiting

Highly Emetogenic Cancer Chemotherapy (HEC)

  • Recommended dose: 24 mg orally 30 minutes before the start of single-day HEC (including cisplatin doses of 50 mg/m2 or greater)

Moderately Emetogenic Cancer Chemotherapy (MEC)

  • Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral

  • Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy and subsequent doses given 4 and 8 hours after the first dose.
  • Maximum dose: 16 mg per dose

Postoperative Nausea/Vomiting 

  • Recommended dose: 16 mg orally 1 hour before the induction of anesthesia
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Parenteral

  • Recommended dose: 4 mg IV (undiluted) immediately before induction of anesthesia or postoperatively (nausea and/or vomiting within 2 hours after surgery)
  • Alternative route: 4 mg IM (undiluted)

Radiation Induced Nausea/Vomiting

  • Recommended dose: 8 mg orally 3 times a day
  • Total Body Irradiation: 8 mg orally 1 to 2 hours before each fraction of radiotherapy administered each day
  • Single High-dose Fraction Radiotherapy to the Abdomen: 8 mg orally 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for 1 to 2 days after the completion of radiotherapy
  • Daily Fractionated Radiotherapy to the Abdomen: 8 mg orally 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for each day radiotherapy is given

Pediatric

Chemotherapy Induced Nausea/Vomiting 

4 to 11 years

  • Recommended dose: 4 mg orally 3 times a day, with the first dose administered 30 minutes before the start of chemotherapy, and subsequent doses 4 and 8 hours after the first dose; then 4 mg orally 3 times a day (every 8 hours) for 1 to 2 days after the completion of chemotherapy

12 years and older

  • Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral, 6 months to 18 years

  • Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy, and subsequent doses given 4 and 8 hours after the first dose
  • Maximum dose: 16 mg (per dose)

Chemotherapy Induced Nausea/Vomiting 

4 to 11 years

  • Recommended dose: 4 mg orally 3 times a day, with the first dose administered 30 minutes before the start of chemotherapy, and subsequent doses 4 and 8 hours after the first dose; then 4 mg orally 3 times a day (every 8 hours) for 1 to 2 days after the completion of chemotherapy

12 years and older

  • Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral, 6 months to 18 years

  • Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy, and subsequent doses given 4 and 8 hours after the first dose
  • Maximum dose: 16 mg (per dose)

Or

Children
  • < 4 years: 0.15 mg/kg/dose IV (Max: 16 mg/dose). Safety and efficacy have not been established for PO formulation
  • 4—11 years: 0.15 mg/kg/dose IV (Max: 16 mg/dose). 12 mg/day PO.
  • >= 12 years: 0.15 mg/kg/dose IV (Max: 16 mg/dose). 16 mg/day PO.
Infants
  • 1—5 months: 0.1 mg/kg IV (single dose). Safety and efficacy have not been established for PO formulation.
  • >= 6 months: 0.15 mg/kg/dose IV (Max: 16 mg/dose IV). Safety and efficacy have not been established for PO formulation.

Neonates

  • Safety and efficacy have not been established.

Side Effects of Ondansetron

The most common

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Common

Rare

Drug Interactions of Ondansetron

Ondansetron may interact with following drugs, supplyments, & may change the efficacy of drugs

Pregnancy & Lactation Ondansetron

FDA Pregnancy Category B

Pregnancy

The safety of ondansetron for se in human pregnancy has not been established. Evaluation of experimental animal studies does not indicate direct or indirect harmful effects with respect to the development of the embryo, or fetus, the course of gestation and peri- and post-natal development. However, as animal studies are not always predictive of human response the use of ondansetron in pregnancy is not recommended.

Lactation

Tests have shown that ondansetron passes into the milk of lactating animals. It is therefore recommended that mothers receiving Zofran should not breast-feed their babies. There is no information on the effects of ondansetron on human fertility.

References

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