Consumer medicine information

Apo-Ondansetron

Ondansetron

BRAND INFORMATION

Brand name

APO-Ondansetron Tablets

Active ingredient

Ondansetron

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Apo-Ondansetron.

What is in this leaflet

Read this leaflet carefully before taking your medicine.

This leaflet answers some common questions about ondansetron.

It does not contain all the available information.

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

The information in this leaflet was last updated on the date listed on the last page. More recent information on this medicine may be available.

Ask your doctor or pharmacist:

  • if there is anything you do not understand in this leaflet,
  • if you are worried about taking your medicine, or
  • to obtain the most up-to-date information.

All medicines have risks and benefits. Your doctor has weighed the risks of you using this medicine against the benefits they expect it will have for you.

Pharmaceutical companies cannot give you medical advice or an individual diagnosis.

Keep this leaflet with your medicine. You may want to read it again.

What this medicine is used for

The name of your medicine is APO-Ondansetron. It contains the active ingredient, ondansetron.

It is used to help stop the nausea and vomiting which can occur after some medical treatments.

Ask your doctor if you have any questions about why this medicine has been prescribed for you.

Your doctor may have prescribed ondansetron for another reason.

This medicine is available only with a doctor's prescription.

How it works

Ondansetron belongs to a group of medicines called serotonin receptor -3 antagonists.

There is no evidence that this medicine is addictive.

Use in children

There is not enough information to recommend the use of this medicine in children four years of age and under.

Before you take this medicine

When you must not take it

Do not take this medicine if:

  • You are taking apomorphine (used to treat Parkinson's disease)
  • You are hypersensitive to, or have had an allergic reaction to, ondansetron or any of the ingredients listed at the end of this leaflet.
    Symptoms of an allergic reaction may include cough, shortness of breath, wheezing or difficulty breathing; swelling of the face, lips, tongue, throat or other parts of the body; rash, itching or hives on the skin; fainting or hayfever-like symptoms.
    If you think you are having an allergic reaction do not take any more of the medicine and contact your doctor immediately or go to the Accident and Emergency department at the nearest hospital.
  • The expiry date (EXP) printed on the pack has passed.
  • The packaging is torn, shows signs of tampering or if it does not look quite right.

If you are not sure whether you should start taking this medicine, talk to your doctor.

Before you start to take it

Tell your doctor if:

  1. You have allergies to:
  • any other serotonin receptor antagonists
  • any other medicines
  • any other substances, such as foods, preservatives or dyes.
  1. You have or have had any medical conditions, especially the following:
  • liver problems
  • problems with your digestive system (i.e. constipation)
  • problems with your heart.
  1. You are currently pregnant or you plan to become pregnant. Do not take this medicine whilst pregnant until you and your doctor have discussed the risks and benefits involved.
  2. You are currently breastfeeding or you plan to breastfeed. Do not take this medicine whilst breastfeeding until you and your doctor have discussed the risks and benefits involved.
  3. You are planning to have surgery or an anaesthetic.
  4. You are currently receiving or are planning to receive dental treatment.
  5. You are taking or are planning to take any other medicines, This includes vitamins and supplements that are available from your pharmacy, supermarket or health food shop.

Some medicines and ondansetron may interfere with each other. These include:

  • apomorphine, to treat Parkinson's Disease.
    Do not take ondansetron whilst taking this medicine.
  • medicines to treat epilepsy
  • tramadol, a pain reliever
  • rifampicin, a type of antibiotic
  • medicines that can change the heart's electrical activity or make it likely to change.

These medicines may be affected by ondansetron or may affect how well it works. You may need different amounts of your medicines, or you may need to take different medicines.

Your doctor may have more information on medicines to be careful with or avoid while taking ondansetron.

Other interactions not listed above may also occur.

How to take this medicine

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

They may be different to the information in this leaflet.

If you do not understand any written instructions, ask your doctor or pharmacist for help.

How much to take

Your doctor or pharmacist will tell you how many tablets you will need to take. This depends on your condition and whether or not you are taking any other medicines.

Do NOT take MORE TABLETS than your doctor tells you to.

Do NOT take the tablets MORE OFTEN than your doctor tells you to.

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

How to take it

Swallow the tablet(s) with a glass of water. Do not crush the tablet(s).

When to take it

Take this medicine at about the same time each day. Taking your medicine at the same time each day will have the best effect. It will also help you remember when to take it.

It does not matter if you take it before, with or after food.

How long to take it for

Continue taking your medicine for as long as your doctor tells you.

Do not stop taking them, or change the dose without first checking with your doctor.

Make sure you have enough to last over weekends and holidays.

If you forget to take it

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 ondansetron 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 are not sure what to do, ask your doctor or pharmacist.

If you have trouble remembering to take your medicine, ask your pharmacist for some hints.

If you take too much (overdose)

If you think that you or anyone else may have taken too much of this medicine, immediately telephone your doctor or the Poisons Information Centre (Tel: 13 11 26 in Australia) for advice. Alternatively go to the Accident and Emergency Department at your nearest hospital.

Do this even if there are no signs of discomfort or poisoning. You may need urgent medical attention.

If you take too much ondansetron, you may have problems seeing, constipation, low blood pressure, fainting or heart problems.

While you are taking this medicine

Things you must do

Tell your doctor that you are taking this medicine if:

  • you are about to be started on any new medicine
  • you plan to have any vaccinations or immunisations
  • you are pregnant or are planning to become pregnant
  • you are breast-feeding or are planning to breastfeed
  • you are about to have any blood tests
  • you are going to have surgery or an anaesthetic or are going into hospital.

Your doctor may occasionally do tests to make sure the medicine is working and to prevent side effects. Go to your doctor regularly for a check-up.

Tell any other doctors, dentists and pharmacists who are treating you that you take this medicine.

Things you must not do

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

Do not take your medicine to treat any other complaints unless your doctor or pharmacist tells you to.

Do not stop taking your medicine, or change the dosage, without checking with your doctor.

Things to be careful of

Be careful while driving or operating machinery until you know how ondansetron affects you.

Side effects

Tell your doctor as soon as possible if you do not feel well while you are taking ondansetron or if you have any questions or concerns.

Do not be alarmed by the following lists of side effects. You may not experience any of them. All medicines can have side effects. Sometimes they are serious but most of the time they are not.

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

This list includes the more common side effects. Mostly, these are mild:

  • headache
  • a sensation of warmth or flushing
  • mild stomach cramps
  • constipation or diarrhoea
  • dry mouth
  • hiccups.

Tell your doctor immediately if you notice any of the following.

These may be serious side effects. You may need medical attention.

  • fixed, staring eyes
  • problems with your eyesight
  • problems moving normally, or
  • shaking or twitching
  • dizziness
  • low blood pressure (which would make you light-headed)
  • liver problems.

If any of the following happen, stop taking your medicine and either tell your doctor immediately or go to Accident and Emergency at your nearest hospital:

  • wheezing or difficulty breathing
  • chest pain or tightness
  • palpitations, or fast or slow or irregular heart beats
  • fainting
  • fits or convulsions
  • swelling to the face, lips, mouth, throat or neck which may cause difficulty in swallowing or breathing or sudden collapse
  • skin rash, lumps or hives.

These are very serious side effects and are usually very rare. You may need urgent medical attention or hospitalisation.

Others side effects not listed above may occur in some patients.

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

In certain medical conditions where ondansetron has been used, blood vessel blockage has occurred. However, this has also happened in conditions when ondansetron has NOT been used. Discuss this with your doctor if you have any concerns.

Allergic reactions

If you think you are having an allergic reaction to ondansetron, do not take any more of this medicine and tell your doctor immediately or go to the Accident and Emergency department at your nearest hospital.

Symptoms of an allergic reaction may include some or all of the following:

  • cough, shortness of breath, wheezing or difficulty breathing
  • swelling of the face, lips, tongue, or other parts of the body
  • rash, itching or hives on the skin
  • fainting
  • hayfever-like symptoms.

After taking this medicine

Storage

Keep your tablets in their original packaging until it is time to take them.

If you take them out of their original packaging they may not keep well.

Keep your medicine in a cool dry place where the temperature will stay below 25°C.

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

Do not leave it on a window sill or in the car.

Heat and dampness can destroy some medicines.

Keep it where children cannot reach it.

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

Disposal

If your doctor or pharmacist tells you to stop taking this medicine or it has passed its expiry date, ask your pharmacist what to do with any medicine that is left over.

Where to go for further information

Pharmaceutical companies are not in a position to give people an individual diagnosis or medical advice. Your doctor or pharmacist is the best person to give you advice on the treatment of your condition.

Product description

What APO-Ondansetron looks like

APO-Ondansetron 4 mg Tablets:
Round white tablets marked "4" on one side

Available in blister packs containing 4 or 10 tablets.

APO-Ondansetron 8 mg Tablets:
Round white tablets marked "8" on one side and a scoreline on the other.

Available in blister packs containing 4 or 10 tablets.

Ingredients

Each tablet contains 4 mg or 8 mg of ondansetron as the active ingredient (as hydrochloride dihydrate).

They also contain the following inactive ingredients:

  • lactose
  • microcrystalline cellulose
  • maize starch
  • magnesium stearate
  • Opadry Y-1-7000 White.

This medicine is gluten-free, sucrose-free, tartrazine-free and other azo dyes-free.

Australian Registration Numbers

APO-Ondansetron 4 mg Tablets: AUST R 152187

APO-Ondansetron 8 mg Tablets: AUST R 152188

Distributor

Apotex Pty Ltd
16 Giffnock Avenue
Macquarie Park, NSW 2113
Australia

Apotex Pty Ltd is the licensee of the registered trademarks AX logo, APO and APOTEX from the registered proprietor, Apotex Inc.

This leaflet was prepared in December 2012

BRAND INFORMATION

Brand name

APO-Ondansetron Tablets

Active ingredient

Ondansetron

Schedule

S4

 

Name of the medicine

Ondansetron (as hydrochloride dihydrate).

Excipients.

Lactose, microcrystalline cellulose, maize starch, magnesium stearate and Opadry Y-1-7000 White. The tablets are gluten free.

Description

Chemical name: (3RS)-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]- 1,2,3,9-tetrahydro-4H-carbazol-4-one hydrochloride dihydrate. Molecular formula: C18H20ClN3O.2H2O. MW: 365.9. CAS: 99614-01-4. Ondansetron hydrochloride dihydrate is a white to off white powder with a melting point of 177°C. It is sparingly soluble in water and alcohol, soluble in methanol and slightly soluble in methylene chloride. It is soluble in saline (0.9% w/v) to about 8 mg/mL. The pKa of ondansetron hydrochloride dihydrate as determined by a solubility procedure is 7.4. The distribution coefficient between n-octanol and water is pH dependent with log D = 2.2 at a pH of 10.6 and log D = 0.6 at a pH of 5.95.
APO-Ondansetron tablets come in two strengths and contain either 4 mg or 8 mg of ondansetron (as hydrochloride dihydrate).

Pharmacology

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 neurons located both in the peripheral and central nervous system. The mechanisms of action in postoperative 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 or 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.

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%). The terminal elimination half-life of ondansetron after oral dosing is 4.1 to 11.6 hours. The half-life may be prolonged in the elderly. Extent of absorption following intramuscular injection into a lateral compartment of the thigh is identical to intravenous injection and absorption is rapid with Tmax occurring approximately ten minutes after administration. The Cmax after intramuscular administration is 61% lower than that following intravenous administration. 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.
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 sulfate conjugation. Although some nonconjugated metabolites have pharmacological 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 P450 enzymes including CYP1A2, CYP2D6 and CYP3A4. This multiplicity of metabolic enzymes capable of metabolising ondansetron means that inhibition or loss of one enzyme (e.g. CYP2D6 genetic deficiency) results in little change in overall rates of ondansetron elimination.
The plasma protein binding is 70 to 76%. The volume of distribution is 1.8 L/kg.
In a study of 21 children aged 3 to 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 to 7 years old) or 4 mg (8 to 12 years old) were reduced. The size of the change was age related with clearance falling from about 300 mL/minute at 12 years of age to 100 mL/minute 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.
Following rectal administration with an ondansetron suppository, peak plasma concentrations of 15 to 40 nanogram/mL are reached in approximately six hours. Plasma concentrations then fall, but at a slower rate than after an oral dose due to continued absorption of ondansetron. The elimination half-life is approximately six hours. Females show a small clinically insignificant increase in half-life when compared to males. The absolute bioavailability of ondansetron from the suppository is approximately 60%. The relative bioavailability of the suppository compared to an 8 mg tablet was 77%.

Clinical Trials

Chemotherapy and radiotherapy induced nausea and vomiting.

Adult studies.

Highly emetogenic chemotherapy.

In a randomised, double blind parallel group study, 420 patients were randomised to receive either an ondansetron 16 mg suppository prior to cisplatin chemotherapy (greater than or equal to 50 mg/m2) on day 1 followed by an ondansetron 16 mg suppository once daily for a further two days, or ondansetron 8 mg intravenously prior to cisplatin chemotherapy followed by ondansetron 8 mg orally twice daily for a further two days. Results from the primary efficacy analysis (i.e. less than or equal to two emetic episodes on day 1) show that an 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 to 3 and overall of days 1 to 3) showed that the ondansetron suppository was less effective. Patients on a 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. Ondansetron 24 mg administered orally was as effective as ondansetron 8 mg given intravenously in controlling acute emesis and nausea induced by cisplatin chemotherapy. One ondansteron 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 (greater than or equal to 500 mg/m2) based chemotherapy (doxorubicin or epirubicin greater than or equal to 40 mg/m2) followed by 8 mg orally three times a day for three to five days or metoclopramide 60 mg intravenously prior to chemotherapy followed by 20 mg orally three times a day for three to five 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 three to five days following chemotherapy. Ondansetron 8 mg intravenously was given prior to cyclophosphamide (greater than or equal to 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 an ondansetron 16 mg suppository once daily for three days or ondansetron 8 mg orally twice daily for three days. The first administration of the suppository and tablet began two hours and one to two hours respectively prior to cyclophosphamide chemotherapy (greater than or equal to 500 mg/m2) on day 1. Results from the primary efficacy analysis (less than or equal to two emetic episodes on the worst day of days 1 to 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 to 3, total number of emetic episodes days 1 to 3 and number of emetic episodes on worst day of days 1 to 3).

Paediatric studies.

Three open label, uncontrolled, noncomparative studies have been performed with 182 patients aged 4 to 18 years with cancer who were given a variety of cisplatin or noncisplatin 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.

Postoperative nausea and vomiting (PONV). Prevention of PONV.

Adults.*

Surgical patients received ondansetron immediately before the induction of general balanced anaesthesia. In a double blind, placebo controlled study ondansetron 4 mg intravenously given to 136 patients 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 to 24 hour postrecovery 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 postoperative nausea and vomiting. Repeat dosing was not undertaken in these studies. Children at greater risk of postoperative nausea and vomiting are more likely to benefit from prophylaxis; this includes children with a history of motion sickness or previous postoperative nausea and vomiting. No comparisons with other drugs for the prevention of nausea and/or vomiting are available.

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, postmarketing 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 hypomagnesia 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.
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.

Carcinogenecity/ genotoxicity/ effects on 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.

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 fetus, the course of gestation, and perinatal and postnatal 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 breastfeed their babies.

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 P450 drug 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 excercised 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 of 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 three 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. 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 (greater than or equal to 1/10), common (greater than or equal to 1/100 and < 1/10), uncommon (greater than or equal to 1/1,000 and < 1/100), rare (greater than or equal to 1/10,000 and < 1/1,000) 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 postmarketing 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 (e.g. 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 received intravenous ondansetron during clinical trials, eleven experienced major cardiovascular events, including three fatalities, which were considered to be drug related by the investigators (one probable, ten 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 greater than or equal to 1% of paediatric patients (either group) in three pivotal clinical trials for prevention of postoperative 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 postoperative nausea and vomiting.
Occasionally local reactions at the site of intravenous injection have been reported.
See Table 3.
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 to 32 mg a day and selected as shown below. The lowest effective dose should be used.

Adults.

Emetogenic chemotherapy and radiotherapy.

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 two 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.
An alternative to intravenous treatment is a single oral dose of up to 24 mg ondansetron taken with oral dexamethasone 12 mg, 1-2 hours before commencing chemotherapy.

Use in children.

Emetogenic chemotherapy and radiotherapy.

Experience is currently limited but ondansetron was effective and well tolerated in children over 4 years of age following chemotherapy, an oral therapy at doses of 4 mg twice daily for up to five 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.

Use in the elderly.

Emetogenic chemotherapy and radiotherapy.

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.

CINV and RINV in elderly patients.

Ondansetron is well tolerated by patients over 65 years of age.

Oral formulation.

No alteration of oral dose or frequency of administration is required.

PONV oral formulations.

For prevention of postoperative nausea and vomiting, the recommended oral dose is 16 mg given 1 hour prior to anaesthesia.
For treatment of established postoperative nausea and vomiting ondansetron administration by injection is recommended.

PONV in children and adolescents (aged 1 month to 17 years).

Oral formulations.

No studies have been conducted on the use of orally administered ondansetron in the prevention or treatment of postoperative nausea and vomiting; slow IV injection (not less than 30 seconds) is recommended for this purpose.

Impaired renal function.

No alteration of daily dosage or frequency of dosing is required.

Impaired hepatic function.

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.

Overdosage

Symptoms.

Little is known at present about overdosage with ondansetron, however, a limited number of patients have received overdoses. Manifestations that have been reported include visual disturbances, severe constipation, hypotension and a vasovagal episode with transient second degree A-V block. In all instances, the events resolved completely.

Treatment.

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 Poisons Information Centre on 131 126 (Australia) for advice on the management of overdosage.

Presentation

Tablets (round, white, film coated), 4 mg (marked 4 on one side), 8 mg (marked 8 on one side, scored on reverse): 4's, 10's (blister pack).

Storage

Store below 25°C.

Poison Schedule

S4.