Consumer medicine information

Onsetron ODT Orally disintegrating tablets

Ondansetron

BRAND INFORMATION

Brand name

Onsetron ODT Orally disintegrating tablets

Active ingredient

Ondansetron

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Onsetron ODT Orally disintegrating tablets.

What is in this leaflet

Please read this leaflet carefully before you start taking ONSETRON ODT.

This leaflet answers some common questions about ONSETRON ODT. It does not contain all of the available information.

It does not take the place of talking to your doctor or pharmacist.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking ONSETRON ODT against the benefits this medicine is expected to have for you.

If you have any concerns about taking this medicine, ask your doctor or pharmacist.

Keep this leaflet with the medicine.

You may need to read it again.

What ONSETRON ODT are used for

ONSETRON ODT belongs to a group of medicines called antiemetics.

ONSETRON ODT works by helping to stop the nausea (sick feeling) and vomiting which can occur after certain treatments. ODT used in the product name stands for Oral Dispersible Tablet. This type of tablet is placed on the tongue where it is rapidly dispersed and can then be swallowed with or without water. It is easier to swallow than ordinary tablets. ONSETRON ODT should only be used to treat the nausea and vomiting for which it has been prescribed.

Your doctor may have prescribed ONSETRON ODT for another reason.

Ask your doctor if you have any questions about why ONSETRON ODT has been prescribed for you.

ONSETRON ODT is not addictive.

Before you take ONSETRON ODT

When you must not take them

Do not take ONSETRON ODT if you are taking apomorphine (used to treat Parkinson’s disease).

Do not take ONSETRON ODT if you have ever had an allergic reaction to ondansetron or any of the ingredients listed at the end of this leaflet.

Symptoms of an allergic reaction may be mild or severe. They usually include some or all of the following: wheezing, swelling of the lips/mouth, difficulty in breathing, hayfever, lumpy rash ("hives") or fainting.

Do not take ONSETRON ODT if you are pregnant, trying to become pregnant or breastfeeding, unless your doctor says you should.

Your doctor will discuss the risks and benefits of using ONSETRON ODT if you are pregnant or breastfeeding.

Do not take ONSETRON ODT after the expiry date (EXP) printed on the pack.

If you take it after the expiry date has passed, it may not work as well.

Do not take ONSETRON ODT if the packaging is torn or shows signs of tampering.

If you're not sure whether you should be taking ONSETRON ODT, talk to your doctor.

Before you start to take them

You must tell your doctor if:

  • you are allergic to foods, dyes, preservatives or any other medicines
  • you have, or used to have, liver problems
  • you suffer from severe constipation or have a blockage in your gut
  • you have phenylketonuria, as ONSETRON ODT contains aspartame.

Taking other medicines

Tell your doctor if you are taking any other medicines, including medicines you buy without a prescription from a pharmacy, supermarket or health food shop.

Some medicines may be affected by ONSETRON ODT, or may affect how well it works. These include:

  • medicines to treat epilepsy
  • tramadol, a pain reliever

Your doctor or pharmacist will be able to tell you what to do if you are taking any of these medicines.

If you are not sure whether you are taking any of these medicines, check with your doctor or pharmacist.

Your doctor and pharmacist have more information on medicines to be careful with or avoid while taking ONSETRON ODT.

Use in children

There is limited experience in children. ONSETRON ODT can be taken by children over 4 years of age.

How to take ONSETRON ODT

Follow all directions given to you by your doctor and pharmacist carefully.

They may differ from the information contained in this leaflet.

If you do not understand the instructions on the packaging, ask your doctor or pharmacist for help.

How much to take

Do not take more tablets than your doctor or pharmacist tells you.

Do not take the tablets more often than your doctor or pharmacist tells you.

If you vomit within one hour of taking your first ONSETRON ODT of each course prescribed for you, you should take the same dose again. If you continue to vomit, tell your doctor.

How to take them

Place the ONSETRON ODT on top of your tongue. It will disperse very quickly, then swallow as normal.

When to take them

Your doctor or pharmacist will be able to tell you when you should take your ONSETRON ODT.

How long to take them

Your doctor or pharmacist will be able to tell you how long you should take your ONSETRON ODT.

If you forget to take them

If you miss your dose and you do not feel sick take your next dose when you are meant to.

If you miss your dose, and you feel sick, take the missed dose as soon as possible, then go back to taking your ONSETRON ODT as you would normally.

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to.

If you take too much (overdose)

Immediately telephone your doctor, or the Poisons Information Centre (telephone 13 11 26), or go to Accident and Emergency at the nearest hospital, if you think you or anyone else may have taken too much ONSETRON ODT. Do this even if there are no signs of discomfort or poisoning.

You may need urgent medical attention.

While you are taking ONSETRON ODT

Things you must do

Before starting any new medicine, tell your doctor or pharmacist that you are taking ONSETRON ODT.

Tell your doctor if you become pregnant or are trying to become pregnant.

Tell your doctor if, for any reason, you have not taken your medicine exactly as prescribed.

Otherwise, your doctor may think that it was not effective and change your treatment unnecessarily.

Things you must not do

Do not give this medicine to anyone else, even if their symptoms seem similar to yours.

Do not use ONSETRON ODT to treat any other complaints unless your doctor says to.

Side-Effects

Tell your doctor or pharmacist as soon as possible if you do not feel well while you are taking ONSETRON ODT.

Like other medicines, ONSETRON ODT can cause some side-effects. If they occur, they are most likely to be minor and temporary. However, some may be serious and need medical attention.

Tell your doctor or pharmacist if you notice any of the following and they worry you:

  • headache
  • a sensation of warmth or flushing
  • mild stomach cramps
  • constipation or diarrhoea
  • dry mouth
  • hiccups
  • dizziness or light-headed feeling

Tell your doctor or pharmacist immediately if you notice any of the following:

  • chest pain or tightness of chest
  • changes in the way your heart beats e.g. if you notice it beating faster or slower than normal, or if it beats irregularly or if it 'throbs'
  • low blood pressure
  • abnormal muscular body movements or shaking involuntary upward movement of the eyes
  • unusual muscle tone causing distortion of the body
  • fits or convulsions

These are serious side-effects. You may need urgent medical attention. Serious side-effects are rare.

If you think you are having an allergic reaction to ONSETRON ODT, tell your doctor immediately or go to the casualty department of your nearest hospital.

Symptoms usually include some or all of the following:

  • wheezing
  • swelling of the lips/mouth
  • difficulty in breathing
  • hay fever
  • lumpy rash ("hives")
  • fainting

Other side-effects not listed above may also occur in some patients. Tell your doctor if you notice anything else that is making you feeling unwell, even if it is not on this list.

Do not be alarmed by this list of possible side-effects. You may not experience any of them.

If your nausea or vomiting does not go away, ask your doctor what to do.

In certain illnesses and treatments where ONSETRON ODT has been used, blood vessel blockage has occurred. However, it is important to note that blood vessel blockage has also occurred in these illnesses and treatments when ONSETRON ODT has not been used. Discuss this with your doctor if you have any concerns.

Ask your doctor or pharmacist if you don't understand anything in this list.

After taking ONSETRON ODT

Storage

Keep this medicine where young children cannot reach it.

A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

Keep ONSETRON ODT in a cool, dry place where it stays below 25°C.

Do not store it, or any other medicine, in a bathroom or near a sink.

Do not leave it in the car or on window sills.

Heat and dampness can destroy some medicines.

Keep your ONSETRON ODT in their pack until it is time to take them.

If taken out of their pack, they may not keep well.

Disposal

If your doctor tells you to stop taking ONSETRON ODT, or they have passed their expiry date, ask your pharmacist what to do with any left over.

Product Description

What it looks like

ONSETRON ODT is a special type of tablet called an Oral Dispersible Tablet.

  • ONSETRON ODT 4 mg tablet is a white, round, flat-faced, bevel-edged tablet. It is available in blister packs of 4 or 10 tablets.
  • ONSETRON ODT 8 mg tablet is a white, round, flat-faced, bevel-edged tablet. It is available in blister packs of 4 or 10 tablets.

Ingredients

Each ONSETRON ODT contains 4 mg or 8 mg of the active ingredient ondansetron.

The inactive ingredients are:

  • Lactose
  • Hydroxypropylcellulose
  • Crospovidone
  • Calcium silicate
  • Aspartame
  • Peppermint NAEFCO P0551 957685 (ARTG 2890) flavour
  • Colloidal anhydrous silica
  • Magnesium stearate.

ONSETRON ODT tablets do not contain gluten.

Sponsor

Medis Pharma Pty Ltd
Level 3, 5 Essex St
The Rocks NSW 2000
Australia

Distributor

Actavis Pty Ltd
Level 5, 117 Harrington St
The Rocks NSW 2000
Australia

Phone: 1800 554 414

Australian Registration Numbers

  • ONSETRON ODT 4 mg:
    AUST R 176761
  • ONSETRON ODT 8 mg:
    AUST R 176762

Date of preparation:
3 April 2014

® Registered Trade Mark

BRAND INFORMATION

Brand name

Onsetron ODT Orally disintegrating tablets

Active ingredient

Ondansetron

Schedule

S4

 

Name of the medicine

Ondansetron.

Excipients.

Lactose, hydroxypropylcellulose, crospovidone, calcium silicate, aspartame, peppermint NAEFCO P0551 957685 (ARTG 2890) flavour, colloidal anhydrous silica and magnesium stearate.

Description

Chemical name:(±)1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl-4H-carbazol-4-one]. Empirical formula: C18H19N3O. Molecular weight: 293.37. CAS No.: 99614-02-5.
Ondansetron is a white to off-white powder with a melting point of 226°C. Ondansetron base is freely soluble in glacial acetic acid, is sparingly soluble in dichloromethane and diluted hydrochloric acid, is slightly soluble in acetonitrile and methanol and is practically insoluble in water.
Onsetron Ondansetron Oral Dispersible Tablet (ODT) is available in 4 mg and 8 mg strengths.
Onsetron ODT contains the following excipients: lactose, hydroxypropylcellulose, crospovidone, calcium silicate, aspartame, peppermint NAEFCO P0551 957685 (ARTG 2890) flavour, colloidal anhydrous silica and magnesium stearate.

Pharmacology

Mode of action.

Ondansetron is a potent, highly selective 5HT3 receptor-antagonist. Its precise mode of action in the control of nausea and vomiting is not known. Chemotherapeutic agents and radiotherapy may cause release of 5HT in the small intestine initiating a vomiting reflex by activating vagal afferents via 5HT3 receptors. Ondansetron blocks the initiation of this reflex. Activation of vagal afferents may also cause a release of 5HT in the area postrema, located on the floor of the fourth ventricle, and this may also promote emesis through a central mechanism. Thus, the effect of ondansetron in the management of the nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy is due to antagonism of 5HT3 receptors on neurones located both in the peripheral and central nervous system. The mechanisms of action in post-operative nausea and vomiting are not known but there may be common pathways with cytotoxic induced nausea and vomiting. In psychomotor testing ondansetron does not impair performance nor cause sedation. Ondansetron does not alter plasma prolactin concentrations.
A study in cloned human cardiac ion channels has shown ondansetron has the potential to affect cardiac repolarisation via blockade of HERG potassium channels. The clinical relevance of this finding is uncertain.

Pharmacokinetics.

Absorption.

Following oral dosing with ondansetron, peak plasma concentrations are achieved in approximately 1.5 hours. For doses above 8 mg the increase in ondansetron systemic exposure with dose is greater than proportional; this may reflect some reduction in first pass metabolism at higher doses. The absolute bioavailability of the ondansetron tablet is approximately 60% (range 36 to 112%).

Distribution.

The plasma protein binding is 70 to 76%. The volume of distribution is 1.8 L/kg.

Metabolism.

Ondansetron is extensively metabolised in humans, with approximately 5% of a radiolabelled dose recovered as the parent compound from the urine. The primary metabolic pathway is hydroxylation on the indole ring followed by glucuronide or sulphate conjugation. Although some nonconjugated metabolites have pharmaceutical activity, these are not found in plasma concentrations likely to significantly contribute to the biological activity of ondansetron. Ondansetron is a substrate for multiple human hepatic cytochrome P-450 enzymes including CYP1A2, CYP2D6 and CYP3A4. This multiplicity of metabolic enzymes capable of metabolising ondansetron means that inhibition or loss of one enzyme (eg. CYP2D6 genetic deficiency) results in little change in overall rates of ondansetron elimination.

Elimination.

The terminal elimination half-life of ondansetron after oral dosing is 4.1 to 11.6 hours and after intravenous dosing 2.5 to 6.1 hours. The half-life may be prolonged in the elderly. In patients with severe hepatic impairment, systemic clearance is markedly reduced with prolonged elimination half-lives (15 to 32 hours) and an oral bioavailability approaching 100% because of reduced presystemic metabolism.

Children.

In a study of 21 children aged 3-12 years receiving elective surgery with general anaesthesia, the clearance and volume of distribution of ondansetron following a single intravenous dose of 2 mg (3-7 years old) or 4 mg (8-12 years old) were reduced. The size of the change was age-related with clearance falling from about 300 mL/min at 12 years of age to 100 mL/min at 3 years. Volume of distribution fell from about 75 L at 12 years to 17 L at 3 years.
The clinical safety of ondansetron in children under 2 years has not been established. Increased incidence of mortality with no specific target organ toxicity has been observed in young rats with immature drug metabolising enzymes.

Clinical Trials

Chemotherapy and radiotherapy induced nausea and vomiting.

Adult studies.

Highly emetogenic chemotherapy.

In a double-blind, randomised study 152 patients were given ondansetron 8 mg intravenously single dose and 173 patients were given 32 mg intravenously single dose 30 minutes prior to Cisplatin (> 50 mg/m2). No significant difference in terms of emesis control or grade of nausea was demonstrated between 8 mg or 32 mg. However, in some studies conducted in patients receiving medium (50-90 mg/m2) or high doses (> 100 mg/m2) of cisplatin chemotherapy, the 32 mg single dose has demonstrated a statistically significant superiority over the 8 mg single dose with regard to control of emesis.
In a double-blind, randomised, cross-over trial, 103 chemotherapy naive patients scheduled to receive cisplatin (50-120 mg/m2) chemotherapy were recruited. Ninety-one patients completed both courses of intravenous ondansetron 0.15 mg/kg (8 mg) x 3 with or without intravenous dexamethasone 20 mg. The combination of ondansetron and dexamethasone was shown to be significantly superior to ondansetron alone.
In a randomised, double-blind parallel group study, 420 patients were randomised to receive either ondansetron 16 mg suppository prior to cisplatin chemotherapy (≥ 50 mg/m2) on day 1 followed by ondansetron 16 mg suppository once daily for a further 2 days, or ondansetron 8 mg intravenously prior to cisplatin chemotherapy followed by ondansetron 8 mg orally twice daily for a further 2 days. Results from the primary efficacy analysis (ie ≤ 2 emetic episodes on day 1) show that the ondansetron suppository and combined ondansetron intravenous and oral regimens are equivalent. However, results from the secondary efficacy analyses (e.g. number of emetic episodes on day 1, the worst day of days 1 - 3 and over all of days 1 - 3) showed that the ondansetron suppository was less effective. Patients on combined ondansetron intravenous and oral regimen remained free of emesis for significantly longer than patients receiving ondansetron suppository.
In a randomised, double-blind, parallel group study 542 patients were randomised to receive either ondansetron tablets (3 x 8 mg) plus dexamethasone capsules (2 x 6 mg), or intravenous ondansetron 8 mg plus intravenous dexamethasone 20 mg, prior to cisplatin infusion. 24 mg of ondansetron administered orally was as effective as ondansetron 8 mg given intravenously in controlling acute emesis and nausea induced by cisplatin chemotherapy. One ondansetron 24 mg tablet has been shown to be bioequivalent to three ondansetron 8 mg tablets.

Emetogenic chemotherapy.

In a double-blind, parallel group study 82 patients were randomised to either ondansetron 8 mg intravenously prior to cyclophosphamide (> 500 mg/m2) based chemotherapy (doxorubicin or epirubicin > 40 mg/m2) followed by 8 mg orally three times a day for 3 to 5 days or metoclopramide 60 mg intravenously prior to chemotherapy followed by 20 mg orally three times a day for 3 to 5 days. Ondansetron was shown to be significantly superior to metoclopramide.
In a randomised, single-blind study, ondansetron 8 mg orally twice daily in 155 patients was compared with ondansetron 8 mg orally three times daily in 153 patients for 3 to 5 days following chemotherapy. Ondansetron 8 mg intravenously was given prior to cyclophosphamide (> 500 mg/m2) based chemotherapy (doxorubicin or epirubicin > 40 mg/m2) on day 1. Ondansetron 8 mg given orally twice daily was as effective as ondansetron 8 mg given orally three times daily.
In a randomised, double-blind parallel group study, 406 patients were randomised to receive either ondansetron 16 mg suppository once daily for 3 days or ondansetron 8 mg orally twice daily for 3 days. The first administration of suppository and tablet began 2 hours and 1-2 hours respectively prior to cyclophosphamide chemotherapy (≥ 500 mg/m2) on day 1. Results from the primary efficacy analysis (≤ 2 emetic episodes on the worst day of days 1-3) show that the ondansetron suppository treatment is equivalent to the ondansetron oral treatment. The ondansetron suppository was less effective than ondansetron oral treatment for a number of other secondary efficacy criteria (complete control of emesis on the worst day of days 1 - 3, total number of emetic episodes days 1 - 3 and number of emetic episodes on worst day of days 1 - 3).

Paediatric studies.

Three open-label, uncontrolled, non-comparative studies have been performed with 182 patients, aged 4-18 years old with cancer who were given a variety of cisplatin or non-cisplatin regimens. In these trials an initial intravenous dose of ondansetron was followed by oral administration of ondansetron. In these studies, 58% of the 170 evaluable patients had no emetic episodes on day 1.

Post-operative nausea and vomiting (PONV).

Prevention of PONV.

Adult studies*.

Surgical patients received ondansetron immediately before the induction of general balanced anaesthesia. In a double-blind, placebo controlled study 136 patients given ondansetron 4 mg intravenously immediately prior to general anaesthesia was significantly more effective than placebo.
In a double-blind, placebo controlled study, 207 patients were given a single oral dose of ondansetron 16 mg, and 204 patients were given placebo one hour prior to induction of anaesthesia. A significantly greater proportion of surgical patients had no emesis during the 0-24 hour post-recovery period compared with placebo.
*The majority of patients included in the prevention of PONV studies using ondansetron have been adult women receiving balanced anaesthesia for gynaecological surgery.

Paediatric studies.

Three, large, double-blind, placebo-controlled studies have been performed in 1,049 male and female patients (2 to 12 years of age) undergoing general anaesthesia with nitrous oxide. The surgical procedures included tonsillectomy with or without adenoidectomy, strabismus surgery, herniorrhaphy, and orchidopexy. Patients were randomised to either single intravenous doses of ondansetron (0.1 mg/kg for children weighing 40 kg or less, a single 4 mg dose for children weighing more than 40 kg) or placebo. Study drug was administered over at least 30 seconds, immediately prior to or following anaesthesia induction. Ondansetron showed significant statistical superiority over placebo in preventing post-operative nausea and vomiting. Repeat dosing was not undertaken in these studies. Children at greater risk of post-operative nausea and vomiting are more likely to benefit from prophylaxis; this includes children with a history of motion sickness or previous post-operative nausea and vomiting. No comparisons with other drugs for the prevention of nausea and/or vomiting are available.

Treatment of PONV.

Adults study*.

In a double-blind study 221 adult surgical patients receiving general balanced anaesthesia, who received no prophylactic anti-emetics and who experienced nausea and/or vomiting within 2 hours post-operatively were evaluated. Patients who experienced an episode of post-operative nausea and/or vomiting were given ondansetron 4 mg intravenously over 2 to 5 minutes, and this was significantly more effective than placebo.
*The majority of patients treated for PONV in studies using ondansetron have been adult women receiving balanced anaesthesia for gynaecological surgery.

Paediatric study.

One, large, double-blind, placebo-controlled study was performed in 351 male and female outpatients (2 to 12 years of age) who received general anaesthesia with nitrous oxide and no prophylactic anti-emetics. Surgical procedures were restricted. Patients who experienced two or more emetic episodes within 2 hours following discontinuation of nitrous oxide were randomised to a single intravenous dose of (0.1 mg/kg for children weighing 40 kg or less, a single 4 mg dose for children weighing more than 40 kg) or placebo administered over at least 30 seconds. Ondansetron demonstrated statistically significant superiority over placebo in preventing further episodes of nausea and vomiting. Repeat dosing was not a feature of this study. No data, involving comparisons with active treatments, have been evaluated.

Indications

Ondansetron is indicated for the prevention and treatment of nausea and vomiting induced by cytotoxic therapy and radiotherapy.

Contraindications

Based on reports of profound hypotension and loss of consciousness when ondansetron was administered with apomorphine hydrochloride, concomitant use with apomorphine is contraindicated.
Hypersensitivity to any component of the preparation. (See Precautions.)

Precautions

Hypersensitivity reactions have been reported in patients who have exhibited hypersensitivity to other selective 5HT3 receptor antagonists.
Ondansetron prolongs the QT interval in a dose-dependent manner. In addition, post-marketing cases of Torsades de Pointes have been reported in patients using ondansetron. 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 patients with electrolyte abnormalities, congestive heart failure, bradyarrhythmias or patients taking other medicinal products that lead to QT prolongation or electrolyte abnormalities.
Hypokalemia and hypomagnesemia should be corrected prior to ondansetron administration.
Serotonin syndrome has been described following the concomitant use of ondansetron and other serotonergic drugs (see Interactions with Other Medicines). If concomitant treatment with ondansetron and other serotonergic drugs is clinically warranted, appropriate observation of the patient is advised.
As ondansetron is known to increase large bowel transit time, patients with signs of subacute intestinal obstruction should be monitored following administration.
Onsetron ODT contains aspartame and therefore should be taken with caution in patients with phenylketonuria.
Repeat dosing has not been studied in paediatric patients who experience nausea and/or vomiting despite receiving ondansetron prophylaxis or who continue to experience symptoms after ondansetron treatment.

Use in pregnancy.

(Category B1)
The safety of ondansetron for use in human pregnancy has not been established. Evaluation of experimental animal studies does not indicate direct or indirect harmful effects with respect to the development of the embryo, or foetus, the course of gestation and peri- and post-natal development. However as animal studies are not always predictive of human response the use of ondansetron in pregnancy is not recommended.

Use in lactation.

Tests have shown that ondansetron is excreted in the breast milk of rats. It is therefore recommended that mothers receiving ondansetron should not breast-feed their babies.

Carcinogenicity/ genotoxicity/ impairment of fertility.

No evidence for carcinogenic activity was found in two year studies at ondansetron doses up to 10 mg/kg/day by gavage in rats or up to 30 mg/kg/day via drinking water in mice. Ondansetron did not induce mutations in Salmonella typhimurium, Escherichia coli or Chinese Hamster Ovary cells in the presence or absence of metabolic activation, and showed no potential for causing chromosomal damage in vitro in peripheral human lymphocytes or in vivo in a mouse micronucleus assay. No evidence for DNA damage was observed with ondansetron in a yeast mitotic gene conversion assay. Oral doses of ondansetron up to 15 mg/kg/day in rats had no effect on male or female fertility.

Interactions

There is no evidence that ondansetron either induces or inhibits the metabolism of other drugs commonly coadministered with it. Specific studies have shown that there are no pharmacokinetic interactions when ondansetron is administered with alcohol, temazepam, alfentanil, furosemide, tramadol or propofol.
Ondansetron is metabolised by multiple hepatic cytochrome P-450 enzymes: CYP3A4, CYP2D6 and CYP1A2. Due to the multiplicity of metabolic enzymes capable of metabolising ondansetron, enzyme inhibition or reduced activity of one enzyme (e.g. CYP2D6 genetic deficiency) is normally compensated by other enzymes and should result in little or no significant change in overall ondansetron clearance or dose requirement.
Caution should be exercised when ondansetron is coadministered with drugs that prolong the QT interval and/or cause electrolyte abnormalities (see Precautions).
Based on reports of profound hypotension and loss consciousness when ondansetron was administered with apomorphine hydrochloride, concomitant use with apomorphine is contraindicated.
In patients treated with potent inducers of CYP3A4 (i.e. phenytoin, carbamazepine, and rifampicin), the oral clearance of ondansetron was increased and ondansetron blood concentrations were decreased.
Following a single 8 mg tablet dose of ondansetron, a threefold to fourfold decrease in the systemic exposure has been seen in adult epileptic subjects maintained on chronic doses of carbamazepine (n = 8) or phenytoin (n = 8) and not receiving chemotherapy. The effect of these enzyme inducing agents on intravenous ondansetron has not been assessed, but the absence of any first pass effects would be expected to result in a smaller change in exposure than seen following oral dosing. Due to the limited efficacy data in subjects on antiepileptics and the many variables that may influence exposure and response, the clinical significance of this drug interaction in cancer patients receiving chemotherapy is not known.

Serotonergic drugs (e.g. SSRIs and SNRIs).

Serotonin syndrome (including altered mental status, autonomic instability and neuromuscular abnormalities) has been described following the concomitant use of ondansetron and other serotonergic drugs, including selective serotonin reuptake inhibitors (SSRIs) and serotonin noradrenaline reuptake inhibitors (SNRIs) (see Precautions).
Data from small studies indicate that ondansetron may reduce the analgesic effect of tramadol.

Adverse Effects

Adverse events are listed below by system organ class and frequency. Frequencies are defined as: very common (≥ 1/10), common (≥ 1/100 and < 1/10), uncommon (≥ 1/1000 and < 1/100), rare (≥ 1/10,000 and < 1/1000) and very rare (< 1/10,000), including isolated reports. Very common, common and uncommon events were generally determined from clinical trial data. The incidence in placebo was taken into account. Rare and very rare events were generally determined from post-marketing spontaneous data.
The following frequencies are estimated at the standard recommended doses of ondansetron according to indication and formulation. The adverse event profiles in children and adolescents were comparable to that seen in adults.

Immune system disorders.

Rare: immediate hypersensitivity reactions, sometimes severe, including anaphylaxis.

Nervous system disorders.

Very common: headache.
Uncommon: seizures, movement disorders (including extrapyramidal reactions such as oculogyric crisis, dystonic reactions and dyskinesia have been observed without definitive evidence of persistent clinical sequelae).
Rare: dizziness during rapid intravenous administration.

Eye disorders.

Rare: transient visual disturbances (eg blurred vision) predominantly during intravenous administration.
Very rare: transient blindness predominantly during intravenous administration.
The majority of the blindness cases reported resolved within 20 minutes. Most patients had received chemotherapeutic agents, which included cisplatin. Some cases of transient blindness were reported as cortical in origin.

Cardiac disorders.

Uncommon: arrhythmias, chest pain with or without ST segment depression, bradycardia.
Rare: QTc prolongation (including Torsades de Pointes).

Vascular disorders.

Common: sensation of warmth or flushing.
Uncommon: hypotension.

Respiratory, thoracic and mediastinal disorders.

Uncommon: hiccups.

Gastrointestinal disorders.

Common: constipation. Xerostomia. Local anal/rectal burning sensation following insertion of suppositories.

Hepatobiliary disorders.

Uncommon: asymptomatic increases in liver function tests#.
#These events were observed commonly in patients receiving chemotherapy with cisplatin.

Skin and subcutaneous tissue disorders.

Very rare: toxic skin eruption, including toxic epidermal necrolysis.

General disorders and administration site conditions.

Common: local intravenous injection site reactions.
To date there has been limited safety experience in controlled trials following intramuscular administration.
Of 7,400 patients who have received intravenous ondansetron during clinical trials, 11 experienced major cardiovascular events, including 3 fatalities, which were considered to be drug-related by the investigators (1 probable, 10 possible). It is well known that cardiovascular events, especially of a vascular occlusive nature are not uncommon among patients with cancer, and these events are further increased with cytotoxic chemotherapy, particularly cisplatin.
Table 1 shows adverse events occurring in ≥ 1% of paediatric patients (either group) in three pivotal clinical trials for prevention of post-operative nausea and vomiting. Ondansetron appears to be as well tolerated as placebo.
The overall incidence of adverse events was similar for ondansetron (53%) and placebo (56%). The most commonly reported adverse events were eye disorder(s) as a result of ophthalmic operations, wound problems at the surgical site, nausea and/or vomiting, drowsiness/sedation, anxiety/agitation and headache. These events are not unexpected in patients undergoing surgery and there was little difference of these between treatment groups. However the incidence of nausea and/or vomiting reported as an adverse event was significantly higher in patients who had received placebo (11%) compared to those who had received ondansetron (6%).
See Table 2. Fewer adverse events were reported with ondansetron (36%) than with placebo (47%). The most common adverse events were similar to those reported in clinical trials for the prevention of post-operative nausea and vomiting.
Occasionally local reactions at the site of intravenous injection have been reported.
The overall incidence rate was 45% in the placebo group and 47% in the intravenous ondansetron group.
The neurological body system was associated with the highest incidence of adverse events (placebo approximately 23%; ondansetron 24%). These events were predominantly headache, dizziness and drowsiness.
Cardiovascular adverse events (bradycardia and hypotension) occurred in approximately 4% in both placebo and ondansetron groups; gastrointestinal adverse events (constipation, nausea/vomiting, flatulence and abdominal pain) occurred in approximately 7% of patients both receiving placebo and intravenous ondansetron.
The incidence rates were generally similar in both treatment groups for all body systems.

Dosage and Administration

The emetogenic potential of cancer treatment varies according to the doses and combinations of chemotherapy and radiotherapy regimens used. The route of administration and dose of ondansetron should be flexible in the range of 8-32 mg a day and selected as shown below. The lowest effective dose should be used.
The Onsetron ODT is administered by placing on top of the tongue where it will rapidly disperse and should then be swallowed with or without water.

Emetogenic chemotherapy and radiotherapy.

Adults.

For the control of chemotherapy or radiotherapy induced emesis or nausea in adults, two oral doses of 8 mg each at 12 hourly intervals may be given, the first dose being administered 2 hours prior to chemotherapy or radiotherapy.
To protect against delayed emesis after the first 24 hours, ondansetron should be continued orally at a dosage of 8 mg twice daily, for up to 5 days after a course of treatment.

Highly emetogenic chemotherapy - adults.

An oral dose of ondansetron 24 mg taken with oral dexamethasone 12 mg, 1-2 hours before commencing chemotherapy can be effective in many patients.
Initial treatment may be followed by oral ondansetron 8 mg 12-hourly for up to 5 days to protect against delayed emesis.

Children.

Experience is currently limited but ondansetron was effective and well tolerated in children over the age of 4 years following chemotherapy, an oral therapy at doses of 4 mg twice daily for up to 5 days can be given.
Repeat dosing has not been studied in paediatric patients who experience nausea and/or vomiting despite receiving ondansetron prophylaxis or who continue to experience symptoms after ondansetron treatment.

Elderly patients.

Efficacy and tolerance in patients aged over 65 years was similar to that seen in younger adults indicating no need to alter dosage or route of administration in the elderly.

Patients with renal impairment.

No alteration of daily dosage or frequency of dosing, or route of administration are required.

Patients with hepatic impairment.

A study which investigated the effect of hepatic impairment on the pharmacokinetics of ondansetron in 24 subjects showed that the plasma clearance of ondansetron is reduced to about 20% of normal, and the serum half-life is significantly prolonged in subjects with severe impairment of hepatic function.
The results in patients with only mildly or moderately impaired hepatic function were less clear. The study showed that in this group the plasma clearance of ondansetron fell to about 50% of that seen in healthy volunteers. Subjects with mild and moderate impairment were not distinguishable from each other for any parameter. This was believed to be partly due to the lack of sensitivity of the Pugh classification system in distinguishing between patients with mild or moderate impairment.
It is recommended that a total daily dose of 8 mg should not be exceeded for patients with moderate or severe hepatic dysfunction. For optimum clinical effect it is recommended that this total daily dose be administered before chemotherapy or radiotherapy.
The severity of the liver disease was assessed according to Pugh's modification of Child's classification [Pugh et al, Brit J. Surg. 1973, 60 (8), 646-649]. Patients with a Pugh score of 5 or less were considered to have good hepatic function. A patient with a score of 6 was graded as having mild hepatic impairment, 7 to 9 as moderate hepatic impairment and 10 or more as severe hepatic impairment. The clinical features used in the grading and the weighting system applied are shown in Table 4.

Patients with poor sparteine/debrisoquine metabolism.

There were no significant differences among poor and extensive debrisoquine categorised metabolisers with regard to ondansetron disposition (area under the curve, total systemic clearance, elimination half-life) following a single 8 mg intravenous dose. The effect of repeated dosing was not investigated, nevertheless dosage adjustments will probably not be required in patients receiving ondansetron by either the oral or intravenous route.

Overdosage

Little is at present known about overdosage with ondansetron, however, a limited number of patients received overdoses. Manifestations that have been reported include visual disturbances, severe constipation, hypotension and a vasovagal episode with transient second degree AV block. In all instances, the events resolved completely. There is no specific antidote for ondansetron, therefore in cases of suspected overdose, symptomatic and supportive therapy should be given as appropriate.
Ondansetron prolongs QT interval in a dose-dependent fashion. ECG monitoring is recommended in cases of overdose.
Contact the Poison Information Centre on 131 126 (Australia) for advice on the management of overdosage.

Presentation

Onsetron ODT 4 mg: White, round 6.6 ± 0.2 mm diameter flat-faced bevel-edged oral dispersible tablets. Each tablet contains ondansetron 4 mg (as free base), in blister packs (Al/Al) of 4 or 10 tablets.
Onsetron ODT 8 mg: White, round 9.1 ± 0.2 mm diameter flat-faced bevel-edged oral dispersible tablets. Each tablet contains ondansetron 8 mg (as free base), in blister packs (Al/Al) of 4 or 10 tablets.

Storage

Store below 25°C.

Poison Schedule

S4.