pms-Ondansetron

Ondansetron.

pms-ONDANSETRON tablets contain either 4 mg or 8 mg of ondansetron base, in the form of ondansetron hydrochloride dihydrate.
Drug Substance: Proper Name: Ondansetron Hydrochloride Dihydrate, USP.
Chemical Name: (±)-1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one, hydrochloride, dihydrate.
Molecular Formula: C₁₈H₁₉N₃O.HCl.2H₂O (hydrochloride dihydrate); C₁₈H₁₉N₃O (base).
Molecular Mass: 365.87 g/mol (hydrochloride dihydrate); 293.4 g/mol (base).
Physicochemical properties: Description and Solubility: Hydrochloride dihydrate: Ondansetron hydrochloride dihydrate is a white to off-white powder. It is soluble at room temperature in either water (~ 32 mg/mL) or normal saline (~ 8 mg/mL) forming a clear and colourless solution. The melting point of ondansetron hydrochloride dihydrate is about 177°C. pKa is 7.4 and pH of 1% w/v solution in water is approximately 4.6. The distribution coefficient between n-octanol and water is pH dependent: log D = 2.2 at a pH of 10.60; log D = 0.6 at a pH of 5.95.
Base: Ondansetron is a white to off-white powder. It is soluble at pH 1.2. Practically insoluble in water. Solubility decreases with increasing pH from very slightly soluble at pH 3.5 and pH 5.4 to practically insoluble at pH 8. Soluble in chloroform and slightly soluble in acetonitrile and methanol.
Excipients/Inactive Ingredients: pms-ONDANSETRON tablets also contain the following excipients (alphabetically): Corn Starch, Croscarmellose Sodium, Lactose, Magnesium Stearate and Microcrystalline Cellulose and a yellow film-coating containing Iron Oxide Yellow, Polyethylene Glycol, Polyvinyl Alcohol, Talc and Titanium Dioxide.

Pharmacology: Mechanism of Action: Ondansetron hydrochloride is a selective antagonist of the serotonin receptor subtype, 5-HT₃. Its precise mode of action in the control of chemotherapy-induced nausea and vomiting is not known.
Cytotoxic chemotherapy and radiotherapy are associated with the release of serotonin (5-HT) from enterochromaffin cells of the small intestine, presumably initiating a vomiting reflex through stimulation of 5-HT₃ receptors located on vagal afferents. Ondansetron may block the initiation of this reflex. Activation of vagal afferents may also cause a central release of serotonin from the chemoreceptor trigger zone of the area postrema, located on the floor of the fourth ventricle. Thus, the antiemetic effect of ondansetron is probably due to the selective antagonism of 5-HT₃ receptors on neurons located in either the peripheral or central nervous systems, or both.
The mechanisms of ondansetron's antiemetic action in post-operative nausea and vomiting are not known.
Pharmacodynamics: In vitro metabolism studies have shown that ondansetron is a substrate for human hepatic cytochrome P₄₅₀ enzymes, including CYP1A2, CYP2D6 and CYP3A4. In terms of overall ondansetron turnover, CYP3A4 played the predominant role. Because of the multiplicity of metabolic enzymes capable of metabolizing ondansetron, it is likely that inhibition or loss of one enzyme (e.g., CYP2D6 enzyme deficiency) will be compensated by others and may result in little change in overall rates of ondansetron clearance.
Electrocardiography: The effect of ondansetron on the QTc interval was evaluated in a double blind, randomized, placebo and positive (moxifloxacin) controlled, crossover study in 58 healthy adult men and women. Ondansetron was tested at single doses of 8 mg and 32 mg infused intravenously over 15 minutes. At the highest tested dose of 32 mg, prolongation of the Fridericia-corrected QTc interval (QT/RR0.33 = QTcF) was observed from 15 min to 4 h after the start of the 15-minute infusion, with a maximum mean (upper limit of 90% CI) difference in QTcF from placebo after baseline-correction of 19.6 (21.5) msec at 20 min. At the lower tested dose of 8 mg, QTc prolongation was observed from 15 min to 1 h after the start of the 15-minute infusion, with a maximum mean (upper limit of 90% CI) difference in QTcF from placebo after baseline-correction of 5.8 (7.8) msec at 15 min. The magnitude of QTc prolongation with ondansetron is expected to be greater if the infusion rate is faster than 15 minutes. The 32 mg IV dose of ondansetron must not be administered.
No treatment-related effects on the QRS duration or the PR interval were observed at either the 8 mg or 32 mg dose. (See Figure 1.)

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An ECG assessment study has not been performed for orally administered ondansetron hydrochloride. On the basis of pharmacokinetic-pharmacodynamic modelling, an 8 mg oral dose of ondansetron hydrochloride is predicted to cause a mean QTcF increase of 0.7 ms (90% CI -2.1, 3.3) at steady-state, assuming a mean maximal plasma concentration of 24.7 ng/mL (95% CI 21.1, 29.0).
The magnitude of QTc prolongation at the recommended 5 mg/m² dose in pediatrics has not been studied, but pharmacokinetic-pharmacodynamic modelling predicts a mean increase of 6.6 ms (90% CI 2.8, 10.7) at maximal plasma concentrations.
Clinical Trials: Pivotal Comparative Bioavailability Studies: A comparative bioavailability study was performed of Pharmascience Inc., pms-ONDANSETRON (ondansetron hydrochloride) 8 mg tablets, versus the reference product, GlaxoSmithKline Inc., ZOFRAN 8 mg tablets, under fasting conditions. The results are summarized in the following table: See Table 1.

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Study Results: Clinical trial results showing the number and percentage of patients exhibiting a complete response to ondansetron (0 emetic episodes) are shown in the following tables for both post-operative and chemotherapy induced emesis. (See Tables 2, 3 and 4.)

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Detailed Pharmacology: Animal Pharmacology: Pharmacodynamics: The ferret provides an excellent model for demonstrating the antiemetic action of drugs. Emesis can be induced by antineoplastic drugs or whole-body irradiation. Behavioural changes associated with these treatments are noted in these animals and may also provide a parallel for the human experience of nausea.
The antiemetic action of ondansetron has been evaluated in both male and female ferrets given cisplatin (9 to 10 mg/kg), cyclophosphamide (200 mg/kg) or irradiation (2 and 8 Gy, 250 kV). IV doses of ondansetron (0.1 to 1 mg/kg) abolished cisplatin-induced emesis for up to 2 hours. In cyclophosphamide-induced emesis, subcutaneous doses of 0.5 mg/kg ondansetron completely eliminated vomiting, significantly reduced retching and delayed the onset of these responses.
The radiation-induced emesis, 0.5 mg/kg ondansetron alone completely and rapidly eliminated retching and vomiting.
The antiemetic effects of ondansetron (0.1 mg/kg) in combination with dexamethasone (2 to 5 mg/kg) were potentiated in ferrets with cyclophosphamide-induced emesis, compared with ondansetron alone. Ondansetron with dexamethasone produced a significant reduction in retching (65%) and vomiting (72%).
Serotonin receptors of the 5-HT₃ type are present both peripherally and on vagal nerve terminals. Ondansetron probably acts by preventing activation of these receptors or receptors located in other regions of the central nervous system. Both the peripheral and central nervous systems appear to be involved since both abdominal vagotomy and microinjection of ondansetron and other 5-HT₃ antagonists directly into the area postrema eliminate cisplatin-induced emesis, while 5-HT₁-like (methiothepin maleate) and 5-HT₂ (ketanserin) antagonists have no effect.
Ondansetron is highly selective for 5-HT₃ receptors and shows negligible binding to other receptors such as 5-HT₁-like, 5-HT₂, α1 and α2 adrenoceptors, β1 and β2 adrenoceptors, D₁ and D₂ muscarinic, nicotinic, GABA_A, H₁ and H₂ receptors.
The pharmacological specificity of ondansetron may explain the observed lack of extrapyramidal side effects often seen following similar therapy with metoclopramide, which preferentially binds to dopamine receptors of the D₂ subtype.
Among its secondary effects, ondansetron has also been shown to cause a dose-dependent increase in the rate of gastric emptying in the guinea pig, which is significant at doses of 0.01 to 0.1 mg/kg. As gastric stasis is frequently associated with nausea, stimulation of gastric motility may be a beneficial action of ondansetron. In the cat, dog and monkey, ondansetron has little effect on heart rate, blood pressure or ECG at IV doses up to 3 mg/kg.
A study in cloned human cardiac ion channels has shown ondansetron has the potential to affect cardiac repolarisation via blockade of hERG potassium channels at clinically relevant concentrations. Dose-dependent QT prolongation has been observed in a thorough QT study in human volunteers (see Electrocardiography as previously mentioned).
Pharmacokinetics: In mice, rats, rabbits and dogs dosed at 1 mg/kg orally and/or intravenously, the plasma half-life of ondansetron was less than 1 hour, but the half-lives of its metabolites were significantly longer. Peak plasma concentrations of ondansetron in rats and dogs ranged from 351 to 419 ng/mL for the IV dose and 8 to 15 ng/mL for the oral dose. Plasma levels were linear over a 30-fold dose range. In repeat-dose studies there was no apparent accumulation of ondansetron.
Ondansetron is almost completely absorbed in animals, and is rapidly metabolized by N-demethylation and hydroxylation of the indole ring, followed by conjugation with glucuronic acid and sulphate. There is significant first-pass metabolism after oral doses.
Ondansetron and its metabolites are rapidly and widely distributed in tissues, reaching higher levels than the corresponding plasma levels. In the rat and dog, ondansetron binds reversibly to tissues containing melanin and elastin. In rats and man, plasma protein binding is about 73%, while it is slightly lower in the dog (60%). Ondansetron and its metabolites cross the blood-brain barrier to only a slight extent.
Human Pharmacology: Pharmacodynamics: In vivo pharmacodynamic studies have investigated the effects of ondansetron on gastric emptying, small bowel transit time and oesophageal motility.
Both oral (16 mg t.i.d) and IV (5 to 10 mg) doses of ondansetron failed to produce a significant effect on gastric emptying in both healthy volunteers and in patients suffering from delayed gastric emptying. However, in one study IV doses of 8 mg did increase gastric emptying in over half the volunteers tested.
IV infusion of either 1 mg or 5 mg ondansetron tended to increase small bowel transit times and single IV doses of 10 mg ondansetron have been reported to decrease sphincter pressure in the lower oesophagus in some subjects.
In psychomotor testing ondansetron does not impair performance nor cause sedation.
Pharmacokinetics: Pharmacokinetic studies in human volunteers showed peak plasma levels of 20 to 30 ng/mL at around 1.5 hours after an 8 mg oral dose of ondansetron. An 8 mg infusion of ondansetron resulted in peak plasma levels of 80 to 100 ng/mL. Repeat dosing of an 8 mg tablet every 8 hours for 6 days increased the peak plasma value to 40 ng/mL. A continuous IV infusion of 1 mg/hour after the initial 8 mg loading dose of ondansetron maintained plasma levels over 30 ng/mL during the following 24-hour period.
The absolute bioavailability of ondansetron in humans was approximately 60% and the plasma protein binding was approximately 73%.
Following oral or IV administration, ondansetron is extensively metabolised and excreted in the urine and faeces. In humans, less than 10% of the dose is excreted unchanged in the urine. The major urinary metabolites are glucuronide conjugates (45%), sulphate conjugates (20%) and hydroxylation products (10%).
The half-life of ondansetron after either an 8 mg oral dose or IV dose was approximately 3 to 4 hours and may be extended to 6 to 8 hours in the elderly.
Mean plasma concentration-time curves for ondansetron following 8 mg and 32 mg dose are shown as follows: See Figure 2.

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In a pharmacokinetic study of 16 epileptic patients maintained chronically on carbamazepine or phenytoin, reduction in AUC, C_max and t_½ of ondansetron was observed. This resulted in a significant increase in clearance. However, on the basis of the inter-subject variability in the available data, no dosage adjustment can be recommended (see Drug-Drug Interactions under Interactions).
Early Phase I studies in healthy elderly volunteers showed a slight age-related decrease in clearance, and an increase in half-life of ondansetron. However, wide inter-subject variability resulted in considerable overlap in pharmacokinetic parameters between young (< 65 years of age) and elderly subjects (≥ 65 years of age) and there were no overall differences in safety or efficacy observed between young and elderly cancer patients enrolled in CINV clinical trials. (See Use in Elderly under Dosage & Administration.)
Based on more recent ondansetron plasma concentrations and exposure-response modeling, a greater effect on QTcF is predicted in patients ≥ 75 years of age compared to young adults. Specific dosing information is provided for patients over 65 years of age and over 75 years of age for IV dosing. (See Use in Elderly under Dosage & Administration.)
Toxicology: Acute Toxicity: Single doses of ondansetron up to the LD₅₀ in mice and in rats were generally well-tolerated. Reactions, including tremor and convulsive behaviour, occurred only at near lethal levels. (See Table 5.)

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All deaths resulted from the acute effects of treatment, the observed clinical signs being consistent with the central nervous system effects associated with behavioural depression. These effects were not associated with any apparent histopathological changes in the brain. No target organ toxicity was identified.
Long-Term Toxicity: Subacute Toxicity Studies: See Table 6.

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Maximum daily dose levels in rats were found to be higher when doses were gradually increased. Identical doses were rapidly lethal to rats not previously exposed to ondansetron. Post-dosing reactions, in both rats and dogs, included ataxia, exophthalmia, mydriasis, tremor and respiratory changes. Increases in liver enzymes (SGPT and SGOT) were noted at high dose levels. Dogs dosed at 6.75 mg/kg/day intravenously exhibited vein irritancy in the form of constriction and thickening, creating resistance to needle penetration. The changes were noted after seven days treatment but were reversed by decreasing the dose concentration.
Chronic Toxicity: See Table 7.

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Carcinogenicity Studies: See Table 8.

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There was no evidence of a tumourigenic effect of ondansetron in any tissue.
Mutagenicity Studies: No evidence of mutagenicity was observed in microbial mutagen tests using mutant strains of Salmonella typhimurium, Escherichia coli or Saccharomyces cerevisiae, with or without a rat-liver post-mitochondrial metabolizing system.
There was also no evidence of damage to genetic material noted in in vitro V-79 mammalian cell mutation studies, in vitro chromosome aberration tests using human peripheral lymphocytes, or in vivo chromosome aberration assays in mouse bone marrow.
Reproduction and Teratology: Ondansetron was not teratogenic in rats and rabbits at dosages up to the maximum non-convulsive level, (rat: 15 mg/kg/day, rabbit: 30 mg/kg/day; the maternal dose was approximately 6 and 24 times the maximum recommended human oral dose of 24 mg/day, respectively, based on body surface area). No adverse effects on pregnancy or fetal and post-natal development were detected in rats and no fetal abnormalities were observed in rabbits after oral administration of ondansetron.
A slight maternal toxicity was observed at the highest dose level in IV organogenesis (4.0 mg/kg/day) studies in the rabbit. Effects included maternal body weight loss and increased incidence of early fetal death. In a rat fertility study, there was a dose-related decrease in the proportion of surviving pups of the F2 generation; however, the significance of this is unclear.
Administration of ondansetron to pregnant rats and rabbits indicated there was fetal exposure to low levels of ondansetron and its metabolites. Ondansetron is retained in the fetal eye presumably bound to melanin. In rats, the transfer of ondansetron and its metabolites into breast milk was extensive. The concentration of unchanged ondansetron in breast milk was higher than in corresponding plasma samples.
Daily administration of ondansetron at dosages up to 15 mg/kg/day to pregnant rats (a maternal dose of approximately 6 times the maximum recommended human oral dose of 24 mg/day, based on body surface area) from day 17 of pregnancy to litter day 22 had no effects on pregnancy of the parental generation or on post-natal development and mating of the F1 generation. Fetal development of the F2 generation was comparable to controls; however, the number of implantations and viable foetuses was reduced in the highest dosage group when compared with controls.
Microbiology: Not applicable.

Adults: pms-ONDANSETRON (ondansetron hydrochloride) is indicated for: the prevention of nausea and vomiting associated with emetogenic chemotherapy, including high dose cisplatin, and radiotherapy; the prevention and treatment of post-operative nausea and vomiting.
Pediatrics (4 to 18 years of age): Post-Chemotherapy Induced Nausea and Vomiting: Ondansetron hydrochloride was effective and well-tolerated when given to children 4 to 12 years of age (see Dosage & Administration). pms-ONDANSETRON is not indicated for the treatment of children 3 years of age or younger.
Post-Radiotherapy Induced Nausea and Vomiting: pms-ONDANSETRON is not indicated for use in any age group of this population.
Post-Operative Nausea and Vomiting: pms-ONDANSETRON is not indicated for use in any age group of this population.
Geriatrics (> 65 years of age): Post-Chemotherapy and Radiotherapy Induced Nausea and Vomiting: Efficacy and tolerance of ondansetron hydrochloride were similar to that observed in younger adults (see Dosage & Administration).
Post-Operative Nausea and Vomiting: Clinical experience in the use of ondansetron hydrochloride in the prevention and treatment of post-operative nausea and vomiting is limited and is not indicated for use in this population.

Note: pms-ONDANSETRON is only available in tablet form. Therefore, when an ondansetron injection is recommended, a product monograph for ondansetron hydrochloride injection should be consulted.
Dosing Considerations: pms-ONDANSETRON has a dose-dependent QTc prolongation effect. For IV administration, the effect is expected to be greater with a faster rate of infusion. Using the minimum effective dose and a slow rate of infusion should always be favored.
Recommended Dose and Dosage Adjustment: Chemotherapy-Induced Nausea and Vomiting: Use in Adults: Highly Emetogenic Chemotherapy (e.g., regimens containing cisplatin): Initial Dose for Prevention of Emesis during the First 24 h Following Chemotherapy: pms-ONDANSETRON (ondansetron hydrochloride) should be given as an initial dose prior to chemotherapy, followed by a dosage regimen tailored to the anticipated severity of emetic response caused by different cancer treatments. The usual dose is ondansetron hydrochloride 8 mg infused intravenously over 15 minutes given at least 30 minutes prior to chemotherapy.
Doses of greater than 8 mg and up to a maximum of 16 mg of ondansetron hydrochloride may only be given by IV infusion. A single-dose greater than 16 mg should not be given due to the dose-dependent risk of QTc prolongation (see Cardiovascular: QTc Interval Prolongation under Precautions; Drug-Drug Interactions: QTc-Prolonging Drugs under Interactions; Pharmacology: Pharmacodynamics: Electrocardiography under Actions).
The efficacy of ondansetron hydrochloride in highly emetogenic chemotherapy may be enhanced by the addition of a single IV dose of dexamethasone sodium phosphate 20 mg administered prior to chemotherapy.
Post-chemotherapy: After the first 24 hours, pms-ONDANSETRON 8 mg may be taken orally every 8 hours¹ for up to 5 days.
¹ The efficacy of twice daily dosage regimens for the treatment of post-chemotherapy emesis has been established only in adult patients receiving less emetogenic chemotherapy. The appropriateness of twice versus three times daily dosage regimens for other patient groups should be based on an assessment of the needs and responsiveness of the individual patient.
Less Emetogenic Chemotherapy (e.g., regimens containing cyclophosphamide, doxorubicin, epirubicin, fluorouracil and carboplatin): Initial Dose: Ondansetron hydrochloride 8 mg infused intravenously over 15 minutes, given at least 30 minutes prior to chemotherapy or pms-ONDANSETRON 8 mg orally 1 to 2 hours prior to chemotherapy.
Post-chemotherapy: pms-ONDANSETRON 8 mg orally twice daily for up to 5 days.
Use in Children: Clinical experience of ondansetron hydrochloride for the treatment of Post-Chemotherapy Induced Nausea and Vomiting in children is currently limited; however, ondansetron hydrochloride was effective and well-tolerated when given to children 4 to 12 years of age. Ondansetron hydrochloride injection should be given intravenously at a dose of 3 to 5 mg/m² over 15 minutes at least 30 minutes before chemotherapy. After therapy, pms-ONDANSETRON 4 mg should be given orally every 8 hours² for up to 5 days. For children 3 years of age and younger, there is insufficient information available to make dosage recommendations; therefore, pms-ONDANSETRON is not indicated for the treatment of children 3 years of age or younger (see Indications/Uses).
Use in Elderly: Oral Formulations: Efficacy and tolerance in patients aged over 65 years were similar to that seen in younger adults indicating no need to alter dosage schedules in this population.
IV Formulation: In patients 65 years of age or older, all IV doses should be diluted in 50 mL to 100 mL of 0.9% Sodium Chloride Injection or 5% Dextrose Injection.
Radiotherapy-Induced Nausea and Vomiting: Use in Adults: Initial Dose: pms-ONDANSETRON 8 mg orally 1 to 2 hours before radiotherapy.
Post-radiotherapy: pms-ONDANSETRON 8 mg orally every 8 hours² for up to 5 days after a course of treatment.
² The efficacy of twice daily dosage regimens for the treatment of post-chemotherapy emesis has been established only in adult patients receiving less emetogenic chemotherapy. The appropriateness of twice versus three times daily dosage regimens for other patient groups should be based on an assessment of the needs and responsiveness of the individual patient.
Use in Children: There is no experience in clinical studies in this population. pms-ONDANSETRON is not indicated for the prevention and treatment of radiotherapy induced nausea and vomiting in children (see Indications/Uses).
Use in Elderly: Efficacy and tolerance in patients aged over 65 years were similar to that seen in younger adults; indicating no need to alter dosage schedules in this population.
Post-Operative Nausea and Vomiting: Use in Adults: For prevention of post-operative nausea and vomiting pms-ONDANSETRON may be administered as a single dose of 16 mg given orally one hour prior to anaesthesia. Alternatively, a single dose of 4 mg of ondansetron hydrochloride, undiluted may be injected intravenously preferably over 2 to 5 minutes, and not less than 30 seconds, at induction of anaesthesia.
For the treatment of established post-operative nausea and vomiting, a single dose of 4 mg of ondansetron hydrochloride, undiluted injected intravenously preferably over 2 to 5 minutes, and not less than 30 seconds, is recommended.
Use in Children: There is no experience in the use of ondansetron hydrochloride in the prevention and treatment of post-operative nausea and vomiting in children. Ondansetron hydrochloride is not indicated for this use in children (see Indications/Uses).
Use in Elderly: There is limited experience in the use of ondansetron hydrochloride in the prevention and treatment of post-operative nausea and vomiting in the elderly. Ondansetron hydrochloride is not indicated for this use in the elderly (see Indications/Uses).
Patients with Renal/Hepatic Impairment: Use in Patients with Impaired Renal Function: No alteration of daily dosage, frequency of dosing, or route of administration is required.
Use in Patients with Impaired Hepatic Function: The clearance of an 8 mg IV dose of ondansetron hydrochloride was significantly reduced and the serum half-life significantly prolonged in subjects with severe impairment of hepatic function. In patients with moderate or severe impairment of hepatic function, reductions in dosage are therefore recommended and a total daily dose of 8 mg should not be exceeded. This may be given as a single IV or oral dose.
No studies have been conducted to date in patients with jaundice.
Patients with Poor Sparteine/Debrisoquine Metabolism: The elimination half-life and plasma levels of a single 8 mg IV dose of ondansetron did not differ between subjects classified as poor and extensive metabolisers of sparteine and debrisoquine. No alteration of daily dosage or frequency of dosing is recommended for patients known to be poor metabolisers of sparteine and debrisoquine.

At present there is little information concerning overdosage with ondansetron. Individual doses of 84 mg and 145 mg and total daily doses as large as 252 mg have been administered with only mild side effects. There is no specific antidote for ondansetron; therefore, in cases of suspected overdosage, symptomatic and supportive therapy should be given as appropriate.
The use of Ipecac to treat overdosage with ondansetron is not recommended as patients are unlikely to respond due to the anti-emetic action of ondansetron itself.
"Sudden blindness" (amaurosis) of 2 to 3 minutes duration plus severe constipation occurred in one patient that was administered 72 mg of ondansetron intravenously as a single-dose. Hypotension (and faintness) occurred in another patient that took 48 mg of oral ondansetron. Following infusion of 32 mg over only a 4-minute period, a vasovagal episode with transient second-degree heart block was observed. Neuromuscular abnormalities, autonomic instability, somnolence, and a brief generalized tonic-clonic seizure (which resolved after a dose of benzodiazepine) were observed in a 12-month-old infant who ingested seven or eight 8 mg ondansetron tablets (approximately forty times the recommended 0.1 to 0.15 mg/kg dose for a pediatric patient). In all instances, the events resolved completely.
Ondansetron prolongs QT interval in a dose-dependent fashion (see Pharmacology: Pharmacodynamics under Actions). ECG monitoring is recommended in cases of overdose.
Cases consistent with serotonin syndrome have been reported in young children following oral overdose.
For management of a suspected drug overdose, contact the regional Poison Control Center.

pms-ONDANSETRON (ondansetron hydrochloride) is contraindicated in patients with a history of hypersensitivity to the drug or any components of its formulations. For a complete listing, see Presentation and Description.
The concomitant use of apomorphine with ondansetron is contraindicated based on reports of profound hypotension and loss of consciousness when apomorphine was administered with ondansetron.

Serious Drug Interactions: Apomorphine (see Contraindications).

Immune: Cross-reactive hypersensitivity has been reported between different 5-HT₃ antagonists. Patients who have experienced hypersensitivity reactions to one 5-HT₃ antagonist have experienced more severe reactions upon being challenged with another drug of the same class. The use of a different 5-HT₃ receptor antagonist is not recommended as a replacement in cases in which a patient has experienced even a mild hypersensitivity type reaction to another 5-HT₃ antagonist.
Cardiovascular: QTc Interval Prolongation: Ondansetron prolongs the QT interval (see Pharmacology: Pharmacodynamics: Electrocardiography under Actions). The magnitude of QTc prolongation will depend on the dose and the infusion rate. In addition, post-marketing cases of torsade de pointes have been reported in patients using ondansetron. Torsade de pointes is a polymorphic ventricular tachyarrhythmia. Generally, the risk of torsade de pointes increases with the magnitude of QTc prolongation produced by the drug. Torsade de pointes may be asymptomatic or experienced by the patient as dizziness, palpitations, syncope, or seizures. If sustained, torsade de pointes can progress to ventricular fibrillation and sudden cardiac death.
Avoid ondansetron in patients with congenital long QT syndrome. Ondansetron should be administered with caution to patients who have or may develop prolongation of QTc, including congestive heart failure, bradyarrhythmias or patients taking other medicinal products that lead to either QT prolongation or electrolyte abnormalities (see Interactions). Hypokalemia, hypocalcemia, and hypomagnesemia should be corrected prior to ondansetron administration.
Additional risk factors for torsade de pointes in the general population include, but are not limited to, the following: female gender; age 65 years or older; baseline prolongation of the QT/QTc interval; presence of genetic variants affecting cardiac ion channels or regulatory proteins; family history of sudden cardiac death at < 50 years; cardiac disease (e.g., myocardial ischemia or infarction, left ventricular hypertrophy, cardiomyopathy, conduction system disease); history of arrhythmias (especially ventricular arrhythmias, atrial fibrillation, or recent conversion from atrial fibrillation); bradycardia (< 50 beats per minute); acute neurological events (e.g., intracranial or subarachnoid haemorrhage, stroke, intracranial trauma); nutritional deficits (e.g., eating disorders, extreme diets); diabetes mellitus; autonomic neuropathy.
Ondansetron hydrochloride is not effective in preventing motion-induced nausea and vomiting.
Neurologic: Serotonin syndrome/Neuroleptic Malignant Syndrome: Cases of life-threatening serotonin syndrome or neuroleptic malignant syndrome-like events have been reported with 5-HT₃ receptor antagonist antiemetics, including ondansetron hydrochloride dihydrate, when given in combination with other serotonergic and/or neuroleptic drugs. Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, coma), autonomic instability (e.g., tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g., hyperreflexia, incoordination) and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). As these syndromes may result in potentially life-threatening conditions, treatment should be discontinued if such events occur and supportive symptomatic treatment should be initiated. If concomitant treatment of ondansetron hydrochloride with a drug affecting the serotonergic neurotransmitter system is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases (see Interactions).
Hepatic/Biliary/Pancreatic: There is no experience in patients who are clinically jaundiced. The clearance of an 8 mg IV dose of ondansetron hydrochloride was significantly reduced and the serum half-life significantly prolonged in subjects with severe impairment of hepatic function. In patients with moderate or severe impairment of hepatic function, reductions in dosage are therefore recommended and a total daily dose of 8 mg should not be exceeded. This may be given as a single IV or oral dose.
Ondansetron does not itself appear to induce or inhibit the cytochrome P₄₅₀ drug-metabolizing enzyme system of the liver. Because ondansetron is metabolised by hepatic cytochrome P₄₅₀ drug-metabolizing enzymes, 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.
Gastrointestinal: As ondansetron is known to increase large bowel transit time, patients with signs of subacute intestinal obstruction should be monitored following administration.
Reproduction: Pregnancy status should be verified for females of reproductive potential prior to starting the treatment with pms-ONDANSETRON.
Females of reproductive potential should be advised that it is possible that ondansetron can cause harm to the developing fetus. Sexually active females of reproductive potential are recommended to use effective contraception (methods that result in less than 1% pregnancy rates) when using pms-ONDANSETRON and for two days after stopping treatment with pms-ONDANSETRON.
Use in Children: Insufficient information is available to provide dosage recommendations for children 3 years of age or younger.

Pregnant Women: The safety of ondansetron for use in human pregnancy has not been established. Ondansetron is not teratogenic in animals. However, as animal studies are not always predictive of human response, the use of ondansetron in pregnancy is not recommended.
Safety data of ondansetron in pregnancy are limited and findings from available pharmacoepidemiologic studies are inconsistent.
Post-marketing reports describe cases of congenital malformations with use of ondansetron during pregnancy; however, the reports are insufficient to establish causal relationship.
Nursing Women: Ondansetron is excreted in the milk of lactating rats. It is not known if it is excreted in human milk, however, nursing is not recommended during treatment with ondansetron.

Clinical Trial Adverse Drug Reactions: Because clinical trials are conducted under very specific conditions the adverse reaction rates observed in the clinical trials may not reflect the rates observed in practice and should not be compared to the rates in the clinical trials of another drug. Adverse drug reaction information from clinical trials is useful for identifying drug-related adverse events and for approximating rates.
Ondansetron hydrochloride has been administered to over 2,500 patients worldwide in controlled clinical trials and has been well-tolerated.
The most frequent adverse events reported in controlled clinical trials were headache (11%) and constipation (4%). Other adverse events include sensations of flushing or warmth (< 1%).
Cardiovascular: There have been rare reports of tachycardia, angina (chest pain), bradycardia, hypotension, syncope and electrocardiographic alterations.
Central Nervous System: There have been rare reports of seizures. Movement disorders and dyskinesia have been reported in two large clinical trials of ondansetron at a rate of 0.1 to 0.3%.
Dermatological: Rash has occurred in approximately 1% of patients receiving ondansetron.
Eye Disorder: Rare cases of transient visual disturbances (e.g., blurred vision) have been reported during or shortly after IV administration of ondansetron, particularly at rates equal to or greater than 30 mg in 15 minutes.
Hypersensitivity: Rare cases of immediate hypersensitivity reactions sometimes severe, including anaphylaxis, bronchospasm, urticaria and angioedema have been reported.
Local Reactions: Pain, redness and burning at the site of injection have been reported.
Metabolic: There were transient increases of SGOT and SGPT of over twice the upper limit of normal in approximately 5% of patients. These increases did not appear to be related to dose or duration of therapy. There have been reports of liver failure and death in patients with cancer receiving concurrent medications including potentially hepatotoxic cytotoxic chemotherapy and antibiotics. The etiology of the liver failure is unclear. There have been rare reports of hypokalemia.
Other: There have been reports of abdominal pain, weakness and xerostomia.
Post-Market Adverse Drug Reactions: Over 250 million patient treatment days of ondansetron hydrochloride have been supplied since the launch of the product worldwide. The following events have been spontaneously reported during post-approval use of ondansetron hydrochloride, although the link to ondansetron cannot always be clearly established.
The adverse event profiles in children and adolescents were comparable to that seen in adults.
Immune Disorders: Rare cases of hypersensitivity reactions, sometimes severe (e.g., laryngeal edema, stridor, laryngospasm and cardiopulmonary arrest) have also been reported.
Cardiovascular Disorders: There have been rare reports (< 0.01%) of myocardial infarction, myocardial ischemia, angina, chest pain with or without ST segment depression, arrhythmias (including ventricular or supraventricular tachycardia, premature ventricular contractions, and atrial fibrillation), electrocardiographic alterations (including second degree heart block), palpitations and syncope.
Rarely and predominantly with IV ondansetron, transient ECG changes including QTc interval prolongation, Torsade de Pointes, ventricular fibrillation, cardiac arrest, and sudden death have been reported (see Cardiovascular under Precautions).
Eye Disorder: There have been very rare cases of transient blindness following ondansetron treatment, generally within the recommended dosing range and predominantly during IV administration.
The majority of blindness cases reported, resolved within 20 minutes. Although most patients had received chemotherapeutic agents, including cisplatin a few cases of transient blindness occurred following ondansetron administration for the treatment of post-operative nausea or vomiting and in the absence of cisplatin treatment. Some cases of transient blindness were reported as cortical in origin.
Hepatobiliary Disorders: Occasional asymptomatic increases in liver function tests have been reported.
Nervous System Disorders: Transient episodes of dizziness (< 0.1%) have been reported predominantly during or upon completion of IV infusion of ondansetron.
Uncommon reports (< 1%) suggestive of extrapyramidal reactions including oculogyric crisis/dystonic reactions (e.g., oro-facial dyskinesia, opisthotonos, tremor, etc.), movement disorders and dyskinesia have been reported without definitive evidence of persistent clinical sequelae.
Serotonin syndrome and neuroleptic malignant syndrome-like events have been reported with 5-HT₃ receptor antagonist antiemetics, including ondansetron hydrochloride, when given in combination with other serotonergic and/or neuroleptic drugs (see Neurologic under Precautions).
Respiratory, Thoracic and Mediastinal Disorders: There have also been rare reports of hiccups.
Skin and Subcutaneous Tissue Disorders: Very rare reports have been received for bullous skin and mucosal reactions, including fatal cases. These reports include toxic skin eruptions, such as Stevens-Johnson syndrome and toxic epidermal necrolysis, and have occurred in patients taking other medications that can be associated with bullous skin and mucosal reactions.

Drug-Drug Interactions: Specific studies have shown that there are no pharmacokinetic interactions when ondansetron is administered with alcohol, temazepam, furosemide, tramadol or propofol.
Ondansetron is metabolised by multiple hepatic cytochrome P₄₅₀ enzymes: CYP3A4, CYP2D6 and CYP1A2. Despite the multiplicity of metabolic enzymes capable of metabolising ondansetron which can compensate for an increase or decrease in enzyme activity, it was found that patients treated with inducers of CYP3A4 (i.e. phenytoin, carbamazepine, and rifampicin) demonstrated an increase in oral clearance of ondansetron and a decrease in ondansetron blood concentrations. No effect in ondansetron clearance secondary to enzyme inhibition or reduced activity (e.g., CYP2D6 genetic deficiency) has been identified to date.
QTc-Prolonging Drugs: The concomitant use of ondansetron hydrochloride with another QTc-prolonging drug should be carefully considered to determine that the therapeutic benefit outweighs the potential risk. Drugs that have been associated with QTc interval prolongation and/or torsade de pointes include, but are not limited to, the examples in the following list. Chemical/pharmacological classes are listed if some, although not necessarily all, class members have been implicated in QTc prolongation and/or torsade de pointes: Class IA antiarrhythmics (e.g., quinidine, procainamide, disopyramide); Class III antiarrhythmics (e.g., amiodarone, sotalol, ibutilide, dronedarone); Class 1C antiarrhythmics (e.g., flecainide, propafenone); antiemetics (e.g., dolasetron, droperidol, chlorpromazine, prochlorperazine); tyrosine kinase inhibitors (e.g., vandetanib, sunitinib, nilotinib, lapatinib); antipsychotics (e.g., chlorpromazine, pimozide, haloperidol, ziprasidone); antidepressants e.g., citalopram, fluoxetine, venlafaxine, tricyclic/tetracyclic antidepressants (e.g., amitriptyline, imipramine, maprotiline); opioids (e.g., methadone); domperidone; macrolide antibiotics and analogues (e.g., erythromycin, clarithromycin, telithromycin, tacrolimus); quinolone antibiotics (e.g., moxifloxacin, levofloxacin, ciprofloxacin); antimalarials (e.g., quinine, chloroquine); azole antifungals (e.g., ketoconazole, fluconazole, voriconazole); histone deacetylase inhibitors (e.g., vorinostat); beta-₂ adrenoceptor agonists (e.g., salmeterol, formoterol).
Drugs that Cause Electrolyte Abnormalities: The use of ondansetron hydrochloride with drugs that can disrupt electrolyte levels should be avoided. Such drugs include, but not limited to, the following: loop, thiazide, and related diuretics; laxatives and enemas; amphotericin B; high dose corticosteroids.
The previous lists of potentially interacting drugs are not comprehensive. Current information sources should be consulted for newly-approved drugs that prolong the QTc interval or cause electrolyte disturbances, as well as for older drugs for which these effects have recently been established.
Tramadol: Data from small studies indicate that ondansetron may reduce the analgesic effect of tramadol.
Apomorphine: Based on reports of profound hypotension and loss of consciousness when ondansetron was administered with apomorphine hydrochloride, concomitant use with apomorphine is contraindicated (see Contraindications).
Serotonergic Drugs: As with other serotonergic agents, serotonin syndrome, a potentially life-threatening condition, may occur with 5-HT₃ receptor antagonist antiemetic treatment when given in combination with other agents that may affect the serotonergic neurotransmitter system (including triptans, SSRIs, SNRIs, lithium, sibutramine, fentanyl and its analogues, dextromethorphan, tramadol, tapentadol, meperidine, methadone, and pertazocine or St. John's Wort [Hypericum perforatum]), and with drugs which impair metabolism of serotonin (such as MAOIs, including linezolid [an antibiotic which is a reversible non-selective MAOI], and methylene blue) (see Neurologic under Precautions).

Store below 25°C. Protect from light.

Antiemetics / Supportive Care Therapy

A04AA01 - ondansetron ; Belongs to the class of serotonin (5HT3) antagonists. Used for the prevention of nausea and vomiting.

P₁S₁S₃