ONDANSETRON HYDROCHLORIDE PRESERVATIVE FREE
Clinical safety rating: safe
Drugs that prolong the QT interval may have additive effects Can cause QT prolongation and subsequent arrhythmias.
Selective 5-HT3 receptor antagonist; blocks serotonin at vagal afferent terminals in the gastrointestinal tract and in the central nervous system chemoreceptor trigger zone.
| Metabolism | Hepatic via CYP1A2, CYP2D6, and CYP3A4 |
| Excretion | Approximately 95% of the dose is metabolized, with less than 5% excreted unchanged in urine. Renal excretion is the primary route for metabolites (about 50% of total elimination). Fecal excretion accounts for approximately 25% of the dose. |
| Half-life | Terminal elimination half-life is approximately 3–6 hours in adults, but may be prolonged to 5–7 hours in elderly patients and up to 20 hours in patients with severe hepatic impairment (Child-Pugh score ≥10). |
| Protein binding | 70–76% bound to plasma proteins, primarily to albumin. |
| Volume of Distribution | Approximately 1.9–2.5 L/kg, indicating extensive distribution into tissues, including the central nervous system. |
| Bioavailability | Oral bioavailability is approximately 60% due to first-pass metabolism. Bioavailability of the orally disintegrating tablet is equivalent to the conventional oral tablet. IM and IV routes provide 100% bioavailability. |
| Onset of Action | IV: 1–2 minutes; oral: 30–60 minutes; orally disintegrating tablet: 30–60 minutes. |
| Duration of Action | Duration of antiemetic effect is 4–8 hours for IV and 8–12 hours for oral administration. Repeat dosing is often required for chemotherapy-induced nausea and vomiting, but a single 8 mg dose may prevent postoperative nausea and vomiting for up to 24 hours. |
8 mg orally or intravenously every 8 hours, or 32 mg intravenously as a single dose 30 minutes before chemotherapy.
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment required for renal impairment. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: maximum total daily dose 8 mg; Child-Pugh C: maximum total daily dose 8 mg. |
| Pediatric use | 0.15 mg/kg/dose intravenously every 4 hours for 3 doses, or 0.15 mg/kg/dose intravenously 30 minutes before chemotherapy; 4 mg orally for children weighing ≤10 kg, 4 mg orally for 11-20 kg, 8 mg orally for >20 kg every 12 hours. |
| Geriatric use | No specific dose adjustment required, but use with caution due to potential QT prolongation risk. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Drugs that prolong the QT interval may have additive effects Can cause QT prolongation and subsequent arrhythmias.
| FDA category | Human |
| Breastfeeding | Present in breast milk in low concentrations; M/P ratio is 0.7. Considered compatible with breastfeeding by the American Academy of Pediatrics; monitor infant for potential adverse effects such as drowsiness or constipation. |
| Teratogenic Risk | First trimester: Limited human data suggest a possible small increased risk of oral clefts; the absolute risk is low. Second and third trimester: No evidence of major teratogenicity. Use only if clearly needed. |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Headache |
| Serious Effects |
["Hypersensitivity to ondansetron or any component of the formulation","Concomitant use with apomorphine"]
| Precautions | ["QT prolongation and torsade de pointes, especially with concomitant electrolyte abnormalities or other QT-prolonging drugs","Serotonin syndrome when coadministered with other serotonergic drugs","Hypersensitivity reactions including anaphylaxis","Masking of progressive ileus or gastric distension after abdominal surgery"] |
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| Fetal Monitoring | Monitor maternal heart rate and ECG for QT prolongation, especially with electrolyte disturbances. Fetal heart rate monitoring is not routinely required but may be considered in cases of prolonged use or high doses. |
| Fertility Effects | No evidence of adverse effects on human fertility; animal studies showed no impairment of fertility at doses up to 15 mg/kg/day. |