a Adverse Events: With the exception of headache, rates of these events were not significantly different in the ondansetron and placebo groups.
b Patients were receiving multiple concomitant perioperative and postoperative medications.
Headache 49 (9%) 27 (5%)
Hypoxia 49 (9%) 35 (7%)
Pyrexia 45 (8%) 34 (6%)
Dizziness 36 (7%) 34 (6%)
Gynecological disorder 36 (7%) 33 (6%)
Anxiety/agitation 33 (6%) 29 (5%)
Urinary retention 28 (5%) 18 (3%)
Pruritus 27 (5%) 20 (4%)
Postmarketing Experience
The following events have been identified during post-approval use of ondansetron. Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. The events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to ondansetron.
Cardiovascular: Rarely and predominantly with intravenous ondansetron, transient ECG changes including QT interval prolongation have been reported.
General: Flushing. Rare cases of hypersensitivity reactions, sometimes severe (e.g., anaphylaxis reactions, angioedema, bronchospasm, shortness of breath, hypotension, laryngeal edema, stridor) have also been reported. Laryngospasm, shock, and cardiopulmonary arrest have occurred during allergic reactions in patients receiving injectable ondansetron.
Hepatobiliary: Liver enzyme abnormalities
Lower Respiratory: Hiccups
Neurology: Oculogyric crisis, appearing alone, as well as with other dystonic reactions
Skin: Urticaria
Eye Disorders: Cases of transient blindness, predominantly during intravenous administration, have been reported. These cases of transient blindness were reported to resolve within a few minutes up to 48 hours.
Drug Interactions
Ondansetron does not itself appear to induce or inhibit the cytochrome P-450 drug-metabolizing enzyme system of the liver [see Clinical Pharmacology (12.3)]. Because ondansetron is metabolized by hepatic cytochrome P-450 drug-metabolizing enzymes (CYP3A4, CYP2D6, CYP1A2), inducers or inhibitors of these enzymes may change the clearance and, hence, the half-life of ondansetron. On the basis of available data, no dosage adjustment is recommended for patients on these drugs.
Apomorphine
Based on reports of profound hypotension and loss of consciousness when apomorphine was administered with ondansetron, the concomitant use of apomorphine with ondansetron is contraindicated [see Contraindications (4)].
Phenytoin, Carbamazepine, Rifampicin
In patients treated with potent inducers of CYP3A4 (i.e., phenytoin, carbamazepine, and rifampicin), the clearance of ondansetron was significantly increased and ondansetron blood concentrations were decreased. In a pharmacokinetic study of 16 epileptic patients maintained chronically on CYP3A4 inducers, carbamazepine, or phenytoin, reduction in AUC, Cmax, and T½ of ondansetron was observed. 1 However, on the basis of available data, no dosage adjustment for ondansetron is recommended for patients on these drugs. 1,3
Tramadol
Although there are no data on pharmacokinetic drug interactions between ondansetron and tramadol, data from two small studies indicate that concomitant use of ondansetron may result in reduced analgesic activity of tramadol. Patients in the studies self administe |
