Overview
11 DESCRIPTION The active ingredient in ondansetron tablets is ondansetron hydrochloride as the dihydrate, the racemic form of ondansetron and a selective blocking agent of the serotonin 5-HT 3 receptor type. Chemically it is (±) 1, 2, 3, 9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one, monohydrochloride, dihydrate.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Ondansetron is a selective 5-HT 3 receptor antagonist. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist. Serotonin receptors of the 5-HT 3 type are present both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema. It is not certain whether ondansetron’s antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine. In humans, urinary 5-hydroxyindoleacetic acid (5-HIAA) excretion increases after cisplatin administration in parallel with the onset of emesis.
Indications
- 1 INDICATIONS AND USAGE Ondansetron tablets are indicated for the prevention of nausea and vomiting associated with: highly emetogenic cancer chemotherapy, including cisplatin greater than or equal to 50 mg/m 2 . initial and repeat courses of moderately emetogenic cancer chemotherapy. radiotherapy in patients receiving either total body irradiation, single high-dose fraction to the abdomen, or daily fractions to the abdomen Ondansetron tablets are also indicated for the prevention of postoperative nausea and/or vomiting.
Common Doses
- 8 mg
- 24 mg
- 50 mg
- 16 mg
Dosage
2 DOSAGE AND ADMINISTRATION See full prescribing information for the recommended dosage in adults and pediatrics (2) Patients with severe hepatic impairment: do not exceed a total daily dose of 8 mg ( 2.2 , 8.6 ) 2.1 Dosage The recommended dosage regimens for adult and pediatric patients are described in Table 1 and Table 2, respectively. Corresponding doses of ondansetron tablets may be used interchangeably. Table 1: Adult Recommended Dosage Regimen for Prevention of Nausea and Vomiting Indication Dosage Regimen Highly Emetogenic Cancer Chemotherapy A single 24 mg dose administered 30...
Contraindications
- 4 CONTRAINDICATIONS Ondansetron is contraindicated in patients: known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any of the components of the formulation [see Adverse Reactions (6.2) ] receiving concomitant apomorphine due to the risk of profound hypotension and loss of consciousness Patients known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any components of the formulation. (4) Concomitant use of apomorphine (4)
Side Effects
- 6 ADVERSE REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions ( 5.1 )] QT Prolongation [see Warnings and Precautions (5.2 )] Serotonin Syndrome [see Warnings and Precautions ( 5.3 )] Myocardial Ischemia [see Warnings and Precautions ( 5.4 )] Masking of Progressive Ileus and Gastric Distension [see Warnings and Precautions [see Warnings and Precautions ( 5.
Interactions
- 7 DRUG INTERACTIONS 7.1 Serotonergic Drugs Serotonin syndrome (including altered mental status, autonomic instability, and neuromuscular symptoms) has been described following the concomitant use of 5-HT 3 receptor antagonists and other serotonergic drugs, including SSRIs and SNRIs. Monitor for the emergence of serotonin syndrome. If symptoms occur, discontinue ondansetron and initiate supportive treatment [see Warnings and Precautions ( 5.3) ]. 7.