Ondansetron (Page 2 of 8)

5.1 Hypersensitivity Reactions

Hypersensitivity reactions, including anaphylaxis and bronchospasm, have been reported in patients who have exhibited hypersensitivity to other selective 5-HT3 receptor antagonists.

5.2 QT Prolongation

Ondansetron prolongs the QT interval in a dose-dependent manner [see Clinical Pharmacology (12.2)]. In addition, postmarketing cases of Torsade de Pointes have been reported in patients using ondansetron. Avoid Ondansetron Injection in patients with congenital long QT syndrome. Electrocardiogram (ECG) monitoring is recommended in patients with electrolyte abnormalities (e.g., hypokalemia or hypomagnesemia), congestive heart failure, bradyarrhythmias, or patients taking other medicinal products that lead to QT prolongation.

5.3 Serotonin Syndrome

The development of serotonin syndrome has been reported with 5-HT3 receptor antagonists. Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, fentanyl, lithium, tramadol, and intravenous methylene blue). Some of the reported cases were fatal. Serotonin syndrome occurring with overdose of Ondansetron Injection alone has also been reported. The majority of reports of serotonin syndrome related to 5-HT3 receptor antagonist use occurred in a post-anesthesia care unit or an infusion center.

Symptoms associated with serotonin syndrome may include the following combination of signs and symptoms: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, with or without gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of Ondansetron Injection and other serotonergic drugs. If symptoms of serotonin syndrome occur, discontinue Ondansetron Injection and initiate supportive treatment. Patients should be informed of the increased risk of serotonin syndrome, especially if Ondansetron Injection is used concomitantly with other serotonergic drugs [see Drug Interactions (7.5), Overdosage (10)].

5.4 Myocardial Ischemia

Myocardial ischemia has been reported in patients treated with ondansetron. In some cases, predominantly during intravenous administration, the symptoms appeared immediately after administration but resolved with prompt treatment. Coronary artery spasm appears to be the most common underlying cause. Therefore, do not exceed the recommended infusion rate of Ondansetron Injection and monitor patients for signs and symptoms of myocardial ischemia during and after administration [see Dosage and Administration (2.1, 2.2) and Adverse Reactions (6.2)].

5.5 Masking of Progressive Ileus and Gastric Distention

The use of Ondansetron Injection in patients following abdominal surgery or in patients with chemotherapy-induced nausea and vomiting may mask a progressive ileus and gastric distention. Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction.

Ondansetron Injection is not a drug that stimulates gastric or intestinal peristalsis. It should not be used instead of nasogastric suction.


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 Distention [see Warnings and Precautions (5.5)]

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

The following adverse reactions have been reported in clinical trials of adult patients treated with ondansetron, the active ingredient of intravenous Ondansetron Injection across a range of dosages. A causal relationship to therapy with Ondansetron Injection (ondansetron) was unclear in many cases.

Chemotherapy-Induced Nausea and Vomiting

T able 2. Adverse Reactions Reported in >5% of Adult Patients Who Received Ondansetron at a Dosage of Three 0.15-mg/kg Doses

Adverse Reaction

Number of Adult Patients With Reaction

Ondansetron Injection 0.15 mg/kg x 3 (n = 419)

Met oclopramide ( n = 156)

P lacebo ( n = 34)













Cardiovascular: Rare cases of angina (chest pain), electrocardiographic alterations, hypotension, and tachycardia have been reported.

Gastrointestinal: Constipation has been reported in 11% of chemotherapy patients receiving multiday ondansetron.

Hepatic: In comparative trials in cisplatin chemotherapy patients with normal baseline values of aspartate transaminase (AST) and alanine transaminase (ALT), these enzymes have been reported to exceed twice the upper limit of normal in approximately 5% of patients. The increases were transient and did not appear to be related to dose or duration of therapy. On repeat exposure, similar transient elevations in transaminase values occurred in some courses, but symptomatic hepatic disease did not occur.

Integumentary: Rash has occurred in approximately 1% of patients receiving ondansetron.

Neurological: There have been rare reports consistent with, but not diagnostic of, extrapyramidal reactions in patients receiving Ondansetron Injection, and rare cases of grand mal seizure.

Other: Rare cases of hypokalemia have been reported.

Po stoperative Nausea and/or Vomiting

The adverse reactions in Table 3 have been reported in ≥2% of adults receiving ondansetron at a dosage of 4 mg intravenous over 2 to 5 minutes in clinical trials.

T able 3. Adverse Reactions Reported in2 % (and with Greater Frequency than the P lacebo Group) of Adult Patients Receiving Ondansetron at a Dosage of 4 mg Intravenous Over 2 to 5 Minutes

Adverse Reactiona,b

Ondansetron Injection4 mg Intravenous(n = 547)

Placebo(n = 547)


92 (17%)

77 (14%)


44 (8%)

37 (7%)

Injection-site reaction

21 (4%)

18 (3%)


10 (2%)

6 (1%)

Cold sensation

9 (2%)

8 (1%)


9 (2%)

3 (<1%)


9 (2%)

2 (<1%)

a Adverse reactions: Rates of these reactions were not significantly different in the ondansetron and placebo groups.
b Patients were receiving multiple concomitant perioperative and postoperative medications.

Ped iatric Use: Rates of adverse reactions were similar in both the ondansetron and placebo groups in pediatric patients receiving ondansetron (a single 0.1-mg/kg dose for pediatric patients weighing 40 kg or less, or 4 mg for pediatric patients weighing more than 40 kg) administered intravenously over at least 30 seconds. Diarrhea was seen more frequently in patients taking Ondansetron Injection (2%) compared with placebo (<1%) in the 1-month to 24-month age-group. These patients were receiving multiple concomitant perioperative and postoperative medications.

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