Consumer medicine information

Tetrabenazine Tablets

Tetrabenazine

BRAND INFORMATION

Brand name

Tetrabenazine

Active ingredient

Tetrabenazine

Schedule

SUMMARY CMI

Tetrabenazine Tablets

Consumer Medicine Information (CMI) summary

The full CMI on the next page has more details. If you are worried about using this medicine, speak to your doctor or pharmacist.

1. Why am I taking Tetrabenazine?

Tetrabenazine tablets contains the active ingredient tetrabenazine. Tetrabenazine is used to treat diseases which cause jerky, irregular, uncontrollable movements such as Huntington's chorea, senile chorea and hemiballismus.

For more information, see Section 1. Why am I taking Tetrabenazine? in the full CMI.

2. What should I know before I take Tetrabenazine?

Do not take if you have ever had an allergic reaction to Tetrabenazine or any of the ingredients listed at the end of the CMI.

Talk to your doctor if you have any other medical conditions, take any other medicines, or are pregnant or plan to become pregnant or are breastfeeding.

For more information, see Section 2. What should I know before I take Tetrabenazine? in the full CMI.

3. What if I am taking other medicines?

Some medicines may interfere with Tetrabenazine and affect how it works.

A list of these medicines is in Section 3. What if I am taking other medicines? in the full CMI.

4. How do I take Tetrabenazine?

Adults: The usual starting dose is one tablet twice a day. This may be increased to up to 8 tablets a day.
Children: The usual starting dose is 1/2 tablet twice a day with increases of 1/2 tablet per day every 3 to 4 days until the desired effect is achieved.

More instructions can be found in Section 4. How do I take Tetrabenazine? in the full CMI.

5. What should I know while taking Tetrabenazine?

Things you should do	Remind any doctor, dentist or pharmacist you visit that you are taking Tetrabenazine. If you are having surgery, tell the surgeon or anaesthetist that you are taking Tetrabenazine. Tell your doctor immediately if you become pregnant while using this medicine. Get up slowly when standing up or getting out of bed as Tetrabenazine may cause light-headedness, dizziness, or faintness.
Things you should not do	Do not stop taking this medicine suddenly or change the dose without checking with your doctor.
Driving or using machines	Be careful driving or operating machinery until you know how Tetrabenazine affects you. Tetrabenazine may cause drowsiness in some people.
Drinking alcohol	Avoid drinking alcohol while taking Tetrabenazine. Alcohol can increase some side effects such as dizziness, drowsiness, and difficulty concentrating.
Looking after your medicine	Store tablets below 30°C in a cool dry place. Keep out of reach of children.

For more information, see Section 5. What should I know while taking Tetrabenazine? in the full CMI.

6. Are there any side effects?

Common side effects include drowsiness, Parkinsonism symptoms such as tremor, balancing problems and excessive salivation, depression, agitation, anxiety, insomnia, confusion, difficulty swallowing or choking attacks. Serious side effects include stiffness or tightness in the arms or legs, irrational thoughts or ideas, or suicidal thoughts or behaviour.

For more information, including what to do if you have any side effects, see Section 6. Are there any side effects? in the full CMI.

FULL CMI

Tetrabenazine Tablets

Active ingredient: Tetrabenazine

Consumer Medicine Information (CMI)

This leaflet provides important information about using Tetrabenazine. You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about using Tetrabenazine.

Where to find information in this leaflet:

1. Why am I taking Tetrabenazine?
2. What should I know before I take Tetrabenazine?
3. What if I am taking other medicines?
4. How do I take Tetrabenazine?
5. What should I know while taking Tetrabenazine?
6. Are there any side effects?
7. Product details

1. Why am I taking Tetrabenazine?

Tetrabenazine tablets contain the active ingredient tetrabenazine. Tetrabenazine works in the central nervous system to prevent the absorption of certain chemicals, such as dopamine and serotonin, which helps to control jerky and irregular movement.

Tetrabenazine is used to treat diseases which cause jerky, irregular or uncontrollable movements such as Huntington's chorea, senile chorea and hemiballismus.

2. What should I know before I take Tetrabenazine?

Warnings

Do not take Tetrabenazine if:

you are allergic to tetrabenazine, or any of the ingredients listed at the end of this leaflet. Some of the symptoms of an allergic reaction include:
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.
Always check the ingredients to make sure you can use this medicine.
you are taking reserpine or levodopa
you are taking a medicine known as a monoamine oxidase inhibitor (MAOI) or you have taken this medicine in the past 2 weeks
you have Parkinson's disease. Tetrabenazine can make pre-existing Parkinsonism worse.
you suffer from depression. Tetrabenazine may cause depression, worsen pre-existing depression, or result in suicidal ideation and behaviour.
you have a galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption. Tetrabenazine tablets contain lactose.

Check with your doctor if you:

Have any other medical conditions including:
abnormal heart rate or rhythm
kidney or liver disease
high or low blood pressure
lactose intolerance or malabsorption
suicidal thoughts or behaviour
take any medicines for any other condition.

Tell your doctor if you know your CYP2D6 metaboliser status. Your CYP2D6 metaboliser status may affect the Tetrabenazine dose you need and the dose of other medicines you may be taking.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Do not take Tetrabenazine if you are pregnant or intend to become pregnant. Tetrabenazine crosses the placenta and may harm your unborn baby.

Do not take Tetrabenazine tablets if you are breast-feeding. Tetrabenazine passes into breast milk.

3. What if I am taking other medicines?

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

Some medicines may interfere with Tetrabenazine and affect how it works. These include:

medicines that affect the brain and nervous system including medicines to treat psychiatric conditions, opioid painkillers and sleeping pills
medicines for high blood pressure, including beta blockers
medicines used to treat psychosis such as haloperidol, and chlorpromazine
metoclopramide used control nausea and vomiting
medicines for abnormal heart rhythms
antibiotics.

Medicines that may increase the effect of Tetrabenazine include:

medicines to treat depression called tricyclic antidepressants, monoamine oxidase inhibitors (MAOIs) or CYP2D6 inhibitors, such as fluoxetine, paroxetine, sertraline, quinidine, duloxetine, terbinafine, and amiodarone.

Tetrabenazine may reduce the effect of the following medicines:

reserpine or levodopa

Check with your doctor or pharmacist if you are not sure about what medicines, vitamins or supplements you are taking and if these affect Tetrabenazine.

4. How do I take Tetrabenazine?

How much to take

Your doctor will decide the best dose for you. Follow your doctor's instructions.
The usual adult dose is one tablet twice a day. The dose may be increased up to 8 tablets a day.
The usual children's dose is 1/2 tablet twice a day with increases of 1/2 tablet per day every 3 to 4 days until the desired effect is achieved
Swallow tablets with a glass of water.

When to take Tetrabenazine

Take your medicine about the same time each day, once in the morning and once in the evening.

If you forget to take Tetrabenazine

Tetrabenazine should be taken regularly at the same time each day.

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

Do not take a double dose to make up for the dose you missed.

This may increase your risk of having an unwanted side effect.

If you take too much Tetrabenazine

If you think that you have taken too much Tetrabenazine, you may need urgent medical attention.

You should immediately:

phone the Poisons Information Centre
(by calling 13 11 26), or
contact your doctor, or
go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

5. What should I know while taking Tetrabenazine?

Things you should do

If you feel light-headed, dizzy or faint when getting out of bed or standing up, get up slowly.

Standing up slowly, especially when you get out of bed or from chairs, will help your body get used to the change in position and blood pressure. If this problem continues or gets worse, talk to your doctor.

Call your doctor straight away if you:

experience symptoms of Parkinsonism, which include unsteadiness, tremors, and excessive salivation. Your doctor may need to adjust your dose of Tetrabenazine.
become pregnant while taking Tetrabenazine.

Remind any doctor, dentist or pharmacist you visit that you are taking Tetrabenazine.

If you are having surgery, tell the surgeon or anaesthetist that you are taking Tetrabenazine. It may affect other medicines used during surgery.

Things you should not do

Do not stop taking Tetrabenazine or change the dose without checking with your doctor.
Do not use Tetrabenazine tablets to treat any condition other than that directed by your doctor.
Do not give Tetrabenazine to anyone else even if they have the same condition as you. It may not be safe for another person to take Tetrabenazine.

Driving or using machines

Be careful before you drive or use any machines or tools until you know how Tetrabenazine affects you.

Tetrabenazine may cause drowsiness in some people.

Drinking alcohol

Tell your doctor if you drink alcohol.

Drinking alcohol while taking Tetrabenazine is not recommended. Alcohol can increase some side effects of Tetrabenazine such as dizziness, drowsiness and difficulty concentrating.

Looking after your medicine

Follow the instructions on the bottle label on how to take care of your medicine.

Store below 30 ⁰C in the bottle until it is time to take it. Store Tetrabenazine in a cool dry place away from moisture, heat or sunlight; for example, do not store it:

in the bathroom or near a sink, or
in the car or on windowsills.

Keep it where young children cannot reach it.

Getting rid of any unwanted medicine

If you no longer need to use this medicine or it is out of date, take it to any pharmacy for safe disposal.

Do not use this medicine after the expiry date.

6. Are there any side effects?

All medicines can have side effects. If you do experience any side effects, most of them are minor and temporary. However, some side effects may need medical attention.

See the information below and, if you need to, ask your doctor or pharmacist if you have any further questions about side effects.

Less serious side effects

Less serious side effects

What to do

Nervous system

Sleepiness or drowsiness
Difficulty sleeping
Memory loss
Changes in muscle tone

Psychiatric

Restlessness
Nervousness or anxiety
Depression
Worsening aggression
Confusion

Gastrointestinal

Nausea or vomiting
Diarrhoea or constipation
Stomach pain
Changes in appetite
Dry mouth
Excessive salivation

Skin

Sweating
Skin rash

Eye disorders

Light sensitivity
Spasmodic movement of the eyeballs into an upward fixed position

Cardiovascular

Slow heart rate
Feeling faint or dizziness
Blood pressure changes

General

Fatigue, weakness, or exhaustion
Lactation
Irregular menstrual cycle

Speak to your doctor if you have any of these less serious side effects and they worry you.

Serious side effects

Serious side effects

What to do

Difficulty swallowing
Choking attacks
Muscle rigidity accompanied by mental changes, sweating, very high fever and fluctuations in blood pressure
Confusion or having thoughts of irrational ideas not shared by others
Suicidal thoughts or behaviour
Uncontrollable movements of the hands, arms, legs, or head (similar to those seen with Parkinson's disease), which may be accompanied by unsteadiness and excessive salivation.

Call your doctor straight away, or go straight to the Emergency Department at your nearest hospital if you notice any of these serious side effects.

Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell.

Other side effects not listed here may occur in some people.

Reporting side effects

After you have received medical advice for any side effects you experience, you can report side effects to the Therapeutic Goods Administration online at www.tga.gov.au/reporting-problems. By reporting side effects, you can help provide more information on the safety of this medicine.

Always make sure you speak to your doctor or pharmacist before you decide to stop taking any of your medicines.

7. Product details

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

What Tetrabenazine contains

Active ingredient (main ingredient)	Tetrabenazine
Other ingredients (inactive ingredients)	Starch Talc Lactose Magnesium stearate Iron oxide yellow
Potential allergens	Lactose

Do not take this medicine if you are allergic to any of these ingredients.

What Tetrabenazine looks like

Tetrabenazine tablets are yellowish coloured and contain 25 mg tetrabenazine as the active ingredient. They are scored and marked with "CL" over "25". They are supplied in bottles containing 112 tablets.

Registration number AUST R 13695

Who distributes Tetrabenazine

iNova Pharmaceuticals (Australia) Pty Limited
ABN: 13 617 871 539
Level 10, 12 Help Street
Chatswood NSW 2067
Tel: 1800 630 056

This leaflet was prepared in November 2022

Published by MIMS December 2022

BRAND INFORMATION

Brand name

Tetrabenazine

Active ingredient

Tetrabenazine

Schedule

1 Name of Medicine

Tetrabenazine.

2 Qualitative and Quantitative Composition

Each tablet contains 25 mg tetrabenazine.
Contains lactose.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Tablet, uncoated.
A cylindrical, biplanar tablet with bevelled edges, yellowish colour. upper face marked CL25, lower face single break bar.

4 Clinical Particulars

4.1 Therapeutic Indications

May be useful for the control of chorea, hemiballismus, tardive and buccolingual dyskinesias and certain dystonic syndromes.

4.2 Dose and Method of Administration

Dosage given below is a guide only. For each patient, the dose of tetrabenazine should be titrated to determine the most appropriate dose. Treatment should be reassessed periodically in the context of the patient's underlying condition and concomitant medications.

Adults.

An initial dosage in adults of 25 mg twice a day is recommended. This can be increased by 25 mg a day every 3 or 4 days until the desired therapeutic effect is achieved, or until 200 mg/day is given, or unwanted side effects intervene.

Children.

In children, 12.5 mg twice a day has been used as an initial dose with increments of 12.5 mg every 3 to 4 days until the desired therapeutic effect is obtained, or an upper limit of 3 mg/kg/day is reached, or unwanted side effects intervene.

Note.

Only very limited information on use in children is available.
Dosage may need to be reduced in patients with impaired renal or hepatic function or in elderly patients.
It is reported that if no improvement is found after 7 to 10 days at the maximum dose then it is unlikely that a higher dose or a longer duration of therapy will benefit the patient.

4.3 Contraindications

Tetrabenazine should not be given closer than one day before or in combination with levodopa or reserpine as it blocks the action of these drugs, particularly the central action.
Tetrabenazine should not be administered to persons with a known sensitivity to tetrabenazine or to any of the excipients.
Tetrabenazine should not be given to patients with parkinsonism or depression, as it may worsen these conditions. It should not be administered within two weeks of treatment with a monoamine oxidase inhibitor (MAOI).
Tetrabenazine is contraindicated during breast-feeding.

4.4 Special Warnings and Precautions for Use

Identified precautions.

As for other CNS active drugs, the effect of combination of tetrabenazine and other central depressants including alcohol should be considered. Tetrabenazine may potentiate the action of antihypertensive drugs.

Depression.

Tetrabenazine may cause depression or worsen pre-existing depression. Cases of suicidal ideation and behaviour have been reported in patients taking the product. Particular caution should be exercised in treating patients with a history of depression or prior suicide attempts or ideation.
If depression or suicidal ideation occurs it should be controlled by reducing the dose and/or initiating antidepressant therapy. If depression or suicidal ideation is profound, or persists, discontinuation of tetrabenazine and initiation of antidepressant therapy should be considered.
MAOI antidepressants should not be used until at least two weeks have elapsed since the last tetrabenazine dose, to avoid restlessness, disorientation and confusion, as well as a potentially serious drug interaction resulting in hypertensive crisis.

Parkinsonism.

Tetrabenazine can induce parkinsonism and exacerbate pre-existing symptoms of Parkinson's disease. The tetrabenazine dose should be adjusted as clinically indicated to minimise this side effect.

Neuroleptic malignant syndrome.

Neuroleptic malignant syndrome is a rare complication of tetrabenazine therapy. Neuroleptic malignant syndrome most often occurs early in treatment or in response to changes in dose. The main symptoms of this condition are mental changes, rigidity, hyperthermia, autonomic dysfunction (sweating and fluctuations in blood pressure) and elevated creatinine phosphokinase levels. If neuroleptic malignant syndrome is suspected tetrabenazine should be withdrawn immediately and appropriate treatment initiated.

QTc.

Tetrabenazine causes a small increase (about 8 msec) in the corrected QT interval. In slow metabolisers this increase may be greater (30 msec). Tetrabenazine should be used with caution with other drugs known to prolong QTc and in patients with congenital long QT syndromes and a history of cardiac arrhythmias (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions).

Dysphagia and choking.

Dysphagia and choking attacks with a possibly consequent bronchopneumonia appear to be the only acutely dangerous adverse effects of tetrabenazine reported so far. If these occur, therapy should be discontinued.

Lactose.

Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malsorption, should not take tetrabenazine tablets as they contain lactose.

Orthostatic hypotension.

Tetrabenazine may induce postural hypotension at therapeutic doses and symptoms may include postural dizziness and fainting. These should be considered in patients who may be vulnerable to hypotension or its effects. Monitoring of vital signs on standing should be considered in patients who are vulnerable to hypotension.

Use in renal impairment.

The use of tetrabenazine in patients with renal insufficiency has not been studied.

Use in the elderly.

No specific studies have been performed in the elderly.

Paediatric use.

No adequately controlled clinical studies have been performed in children.

Effects on laboratory tests.

There are no special requirements to monitor effects on laboratory tests.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Interaction may occur when the following medications are administered with tetrabenazine (see Section 4.3 and Section 4.4).

Reserpine and levodopa.

Inhibit the action of these drugs and thereby attenuate their effects.

MAOIs.

Possible serious interactions resulting in hypertensive crisis. At least 14 days should elapse between the discontinuation of a MAOI and initiation of treatment with tetrabenazine.

Tricylic antidepressants.

Have been reported to antagonise the locomotor activity induced by tetrabenazine in animals.

CNS stimulants and depressants.

Possible additive sedative effects should be considered when used in conjunction with CNS depressants (including alcohol, neuroleptics, hypnotics and opioids).

Neuroleptic agents.

Potential for significant dopamine depletion when administering with neuroleptic agents, e.g. haloperidol, chlorpromazine and metoclopramide. Patients should be monitored clinically for the development of parkinsonism. Neuroleptic malignant syndrome has been observed in isolated cases.

Antihypertensives.

May increase risk of orthostatic hypotension.

Beta-blockers.

May increase risk of orthostatic hypotension.

CYP2D6 inhibitors.

In vitro and in vivo studies indicate that tetrabenzine and its metabolites α and β-dihydotetrabenazine are substrates for CYP2D6. β-HTBZ was also an inhibitor of CYP2D6 at clinically relevant concentrations. Caution should be used when adding a CYP2D6 inhibitor (such as fluoxetine, paroxetine, quinidine, duloxetine, terbinafine, amiodarone, or sertraline) to a patient already receiving a stable dose of tetrabenazine or if the dose is influenced by the patient's CYP2D6 metaboliser status. A reduction in the dose of tetrabenazine should be considered.

Antipsychotics, antibiotics and class Ia and III antiarrythmic medications.

Tetrabenazine causes a small increase (about 8 msec) in the corrected QT interval.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

There are no data available on the potential of tetrabenazine to affect fertility.
(Category B3)
There is inadequate evidence of safety of the drug in human pregnancy, and the potential risk to humans is unknown. Tetrabenazine crosses the placenta and, because of the lack of data, tetrabenazine should not be used during pregnancy. In the developmental toxicity tests there was no evidence of in utero mortality, growth retardation or teratogenicity in either rats or rabbits at oral doses up to 5 and 27 times the clinical dose based on body surface area. When tetrabenazine was administered orally to female rats from the beginning of organogenesis to weaning, an increase in stillbirths and postnatal mortality was observed from 15 mg/kg/day, while delayed development was seen at 30 mg/kg/day. The no effect dose for neonatal effects (5 mg/kg/day) was approximately equivalent to the clinical dose based on body surface area. The relative contributions of in utero and neonatal exposure and postnatal maternal neglect to these effects are unclear.
Tetrabenazine is excreted in milk. Oral administration to rats from early gestation to weaning was associated with increased stillbirths, hypothermia and neonatal mortality in pups (15 mg/kg/day, twice the clinical dose based on body surface area), and delayed pup development (30 mg/kg/day, 5-fold the clinical dose). The relative contributions of in utero and neonatal exposure and postnatal maternal neglect to these effects are unclear. Tetrabenazine is contraindicated during breast-feeding.

4.7 Effects on Ability to Drive and Use Machines

As drowsiness may occur in up to 20% of patients, caution should be used when driving or operating machines until competence to do so under treatment has been established. It might be possible to reduce the drowsiness by careful dosage adjustment, especially initially.

4.8 Adverse Effects (Undesirable Effects)

Side effects include drowsiness, depression (which has on occasion been reported to be associated with suicidal ideation and behaviour) and parkinsonism.
The most commonly reported side effects are as follows (see Table 1).
Other adverse reactions which have been reported are as follows (see Table 2).
Neuroleptic malignant syndrome (NMS) associated with the use of tetrabenazine has been reported rarely. This may occur soon after initiation of therapy, following an increase in dosage or after prolonged treatment. The main symptoms are mental changes, rigidity, hyperthermia, autonomic dysfunction and elevated creatinine phosphokinase levels. If NMS is suspected tetrabenazine should be withdrawn and appropriate supportive therapy instituted; treatment with dantrolene and bromocriptine may be effective.

Reporting suspected adverse effects.

Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at www.tga.gov.au/reporting-problems.

4.9 Overdose

Signs and symptoms of overdosage may include nausea, vomiting, diarrhoea, confusion, hallucinations, sedation, drowsiness, sweating, hypotension and hypothermia.
Management should be supportive. There is no information available on the effect of pharmacological antagonists or of dialysis.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Tetrabenazine is a synthetic derivative of benzylquinolizine that causes depletion of dopamine and other monoamines in the central nervous system.
Studies conducted in vitro have shown that tetrabenazine is an inhibitor of monoamine transportation into presynaptic neuronal vesicles, by inhibition of VMAT2 (vesicular monamine transporter 2), which is principally located in the central nervous system. Dihydrotetrabenazine, the principal metabolite of tetrabenazine, has a similar affinity and more significant selectivity for VMAT2, and both compounds are believed to contribute to the pharmacological effect.
At a synaptic level tetrabenazine creates a reversible depletion of monamines in the presynaptic vesicles. Animal studies have shown that tetrabenazine causes preferential depletion of dopamine from nerve terminals in the CNS but neurotransmitter depletion by a single dose of tetrabenazine is reversible and lasts only a few hours. This pharmacological effect explains the therapeutic benefit of tetrabenazine in patients suffering from hyperkinetic movement disorders.

5.2 Pharmacokinetic Properties

Absorption.

Based on metabolite levels, tetrabenazine is quickly and mostly absorbed after oral administration. Its absorption is not affected by the taking of food.
After administration of single doses from 12.5 to 50 mg of tetrabenazine, for the metabolites alpha and beta-dihydrotetrabenazine, the maximum plasma concentration and the area under the curve increased approximately in proportion to the dose, indicating a linear kinetic.
Clinical testing has shown that a single oral dose of tetrabenazine undergoes extensive (> 75%) absorption from the gastrointestinal tract.

Metabolism.

The metabolism of tetrabenazine is complex, initially proceeding via the formation of alpha and beta-dihydrotetrabenazine. The majority of the observed metabolites appear to be formed from these dihydrotetrabenazines as a result of O-dealkylation, hydroxylation and conjugation.
No significant build up has been observed after daily administration. The elimination half-life of dihydrotetrabenazine is approximately 5 to 6 hours.

Excretion.

Tetrabenazine is mostly eliminated in metabolised form in urine.

5.3 Preclinical Safety Data

Genotoxicity.

Tetrabenazine and its major metabolites, α-dihydrotetrabenazine and β-dihydrotetrabenazine, were negative in the in vitro bacterial reverse mutation assay. Tetrabenazine was clastogenic in the in vitro chromosome aberration assay in Chinese hamster ovary cells in the presence of metabolic activation, while α-dihydrotetrabenazine and β-dihydrotetrabenazine were clastogenic in Chinese hamster lung cells in the presence and absence of metabolic activation. In vivo micronucleus tests in rats and mice with tetrabenazine were negative. The genotoxic potential of tetrabenazine is considered to be low.

Carcinogenicity.

A six month study in transgenic p53(+/-) heterozygous mice and a long term study in male rats at oral doses up to 30 mg/kg/day and 6 mg/kg twice daily, respectively, did not provide any evidence of carcinogenic potential. These doses correspond to exposures approximately 3 to 4 times the clinical exposure, based on plasma AUC or dose based on body surface area. Mammary gland hyperplasia was observed in female rats that received twice daily oral doses of 7.5 mg/kg or greater for 6 months associated with exposures (plasma AUC) similar to the clinical exposure. As the effect of tetrabenazine on prolactin levels is not known, the relevance of this finding is uncertain.

6 Pharmaceutical Particulars

6.1 List of Excipients

Lactose, monohydrate, maize starch, purified talc, magnesium stearate and iron oxide yellow.

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of this medicine.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 30°C.

6.5 Nature and Contents of Container

HDPE Bottle: 112 tablets.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking to your local pharmacy.

6.7 Physicochemical Properties

The chemical name of tetrabenazine is 1,3,4,6,7,11b-hexahydro- 9,10-dimethoxy-3- (2-methylpropyl)- 2H-benzo -[a]quinolizin-2-one. Tetrabenazine is white to slightly yellow crystalline powder. Tetrabenazine is soluble in hot water, but practically insoluble in acetone. UV max (alcohol): 230, 284 nanometer (E 7780, 3820).

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Tetrabenazine Tablets

Tetrabenazine

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BRAND INFORMATION

Tetrabenazine Tablets 25 mg