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Author: Admin | 2025-04-28
For signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) and diminished tramadol efficacy when these agents are combined. Monitor therapy Adverse ReactionsNote: Percentages reported in adult patients unless otherwise specified.>10%:Central nervous system: Headache (oral: 9% to 27%; IV: 17%), fatigue (oral: ≤9% to 13%), malaise (oral: ≤9% to 13%)Gastrointestinal: Constipation (6% to 11%)1% to 10%:Central nervous system: Drowsiness (IV: ≤8%), sedation (IV: ≤8%), (dizziness (7%), agitation (oral: ≤6%), anxiety (oral: ≤6%), paresthesia (IV: 2%), sensation of cold (IV: 2%)Dermatologic: Pruritus (2% to 5%), skin rash (1%)Gastrointestinal: Diarrhea (oral: 6% to 7%; IV: Children 1 to 24 months of age: 2%)Genitourinary: Gynecologic disease (oral: 7%), urinary retention (oral: 5%)Hepatic: Increased serum ALT (>2 times ULN: 1% to 5%; transient), increased serum AST (>2 times ULN: 1% to 5%; transient)Local: Injection site reaction (IV: 4%; includes burning sensation at injection site, erythema at injection site, injection site pain)Respiratory: Hypoxia (oral: 9%)Miscellaneous: Fever (2% to 8%) Warnings/PrecautionsConcerns related to adverse effects:Hypersensitivity: Hypersensitivity reactions (including anaphylaxis and bronchospasm) have been reported; discontinue if hypersensitivity occurs. Use with caution in patients allergic to other 5-HT3 receptor antagonists; cross-reactivity has been reported. QT prolongation: ECG changes, including dose-dependent QT interval prolongation, have been observed with ondansetron use. Cases of torsades de pointes have also been reported. Selective 5-HT3 antagonists, including ondansetron, have been associated with a number of dose-dependent increases in ECG intervals (eg, PR, QRS duration, QT/QTc, JT), usually occurring 1 to 2 hours after IV administration. Single doses >16 mg ondansetron IV are no longer recommended due to the potential for an increased risk of QT prolongation. In most patients, these changes are not clinically relevant; however, when used in conjunction with other agents that prolong these intervals or in those at risk for QT prolongation, arrhythmia may occur. When used with agents that prolong the QT interval (eg, Class I and III antiarrhythmics) or in patients with cardiovascular disease, clinically relevant QT interval prolongation may occur resulting in torsades de pointes. A number of trials have shown that 5-HT3 antagonists produce QT interval prolongation to variable degrees. Avoid ondansetron use in patients with congenital long QT syndrome. Use caution and monitor ECG in patients with other risk factors for QT prolongation (eg, medications known to prolong QT interval, electrolyte abnormalities [hypokalemia or hypomagnesemia], heart failure, bradyarrhythmias, and cumulative high-dose anthracycline therapy). Reduction in heart rate may also occur with the 5-HT3 antagonists. IV formulations of 5-HT3 antagonists have more association with ECG interval changes, compared to oral formulations. Serotonin syndrome: Serotonin syndrome has been reported with 5-HT3 receptor antagonists, predominantly when used in combination with other serotonergic agents (eg, SSRIs, SNRIs, MAOIs, mirtazapine, fentanyl, lithium, tramadol, and/or methylene blue). Some of the cases have been fatal. The majority of serotonin syndrome reports due to 5-HT3 receptor antagonist have occurred in a postanesthesia setting or in an infusion center. Serotonin syndrome has also been reported following overdose of ondansetron. Monitor patients for signs of
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