Ondansetron
Trade names

Zofran

Clinical data
Drug class

Antiemetic

Uses

Prevention and treatment of postoperative nausea and vomiting

Contraindications

Prolonged QT interval Patients taking apomorphine

Routes of administration

PO, IM, IV

Dosage
Pharmacodynamics
Mechanism of action

5HT3 antagonist

Adverse effects

Cardiac arrhythmias, cardiac arrest, constipation, headaches

Pharmacokinetics
Metabolism

Liver oxidation followed by glucuronidation and sulfate conjugation

Elimination half-life

4 hours

Physical and chemical data
Article quality
Editor rating
Comprehensive
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Ondansetron is a 5HT3 receptor antagonist that is commonly used for the prevention and treatment of postoperative nausea and vomiting.

Uses

  • Prevention and treatment of postoperative nausea and vomiting
  • Commonly used to treat many other causes of nausea and vomiting[1]

Contraindications

Absolute contraindications

  • Prolonged QT intervals
  • Patients taking apomorphine [1] as it can cause hypotension and loss of consciousness

Precautions

  • Maximum dose of 16 mg IV due to risk of QT prolongation and arrhythmias
  • Maximum dose decreased to 8 mg IV or 8 mg PO in severe hepatic impairment
  • Dissolving tablets formulations contain phenylalanine which can lead to irreversible neurological damage in phenylketonuria (PKU)[1]

Pharmacology

Pharmacodynamics

Mechanism of action

  • Antagonism of the 5HT3 receptors
  • Centrally, ondansetron antagonizes the 5HT3 receptors in the area postrema [1]
  • Peripherally, ondansetron antagonizes the 5HT3 receptors on the vagus nerve within the GI tracts which forms synapses within the nucleus tracts solitarius [1]
    • Predominant mechanism for its anti-emetic effect

Adverse effects

  • Cardiac arrhythmia
  • Cardiac arrest
  • Constipation
  • Headache
  • dry mouth
  • malaise
  • drowsiness
  • sedation
  • pruritus
  • transient elevation in liver function test

Pharmacokinetics

  • Peak plasma concentration about 1.5 hours after an 8 mg PO dose
  • Plasma half life is approximately 4 hours[2]
  • Metabolized by CYP2D6, CYP3A4, CYP2E1, CYP1A2 initially with oxidation followed by glucuronide and sulfate conjugations [1]
    • Many polymorphisms with four different phenotypes
      • Poor metabolizer (no functional allele)
      • Intermediate metabolizer (less activity than one functional allele)
      • Extensive metabolizer (two functional allele, most common phenotype)
      • Ultrarapid metabolizer (three functional allele)

Chemistry and formulation

Available in PO, intramuscular (IM), and intravenous (IV).

History

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Griddine, Alexandria; Bush, Jeffrey S. (2022), "Ondansetron", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 29763014, retrieved 2023-01-05
  2. Zabirowicz, Eric S.; Gan, Tong J. (2019), "Pharmacology of Postoperative Nausea and Vomiting", Pharmacology and Physiology for Anesthesia, Elsevier, pp. 671–692, retrieved 2023-01-05