Consumer medicine information

What is in this leaflet

This leaflet answers some common questions about the Phenobarb tablets.

It does not contain all 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 Phenobarb tablets against the benefits they expect it will 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 Phenobarb tablets are used for

Phenobarb tablets contain the active ingredient Phenobarbital, which belongs to a group of medicines called barbiturates. Barbiturates act by inducing sleep and stopping convulsions.

Phenobarb tablets are used for:

• epileptic fits
• sedation.

Ask your doctor if you have any questions about why Phenobarb tablets have been prescribed for you. Your doctor may have prescribed it for another purpose.

It is available only with a doctor's prescription.

The use of barbiturates may lead to dependence on the medicine.

Before you take it

When you must not take it

Do not take Phenobarb tablets if you are allergic to:
Phenobarbital, other barbiturates or any other ingredients listed at the end of this leaflet.

Some of the symptoms of an allergic reaction may include red, itchy skin rashes, difficulty breathing, hayfever, swelling of the face or throat or faintness.

Phenobarb tablets should not be used if you have or have had any of the following medical conditions:

• porphyria, a rare blood pigment disorder
• anaemia, a disease of the blood with reduced number of red blood cells
• severe breathing difficulties
• uncontrolled severe asthma
• uncontrolled diabetes mellitus or sugar diabetes
• alcoholism or drug dependence
• liver or kidney problems
• severe depression or suicidal tendencies
• or long term pain.

Phenobarb tablets should not be given to unusually overactive children.

Do not take this medicine after the expiry date (EXP.) printed on the pack.

Do not take it if the packaging shows signs of tampering or the tablets do not look quite right.

Before you start to take it

Tell your doctor if you are pregnant or intend to become pregnant. Phenobarb tablets may harm your developing baby if you take it during pregnancy. However, it is very important to control your fits while you are pregnant. Phenobarbital should not be used during pregnancy unless the potential benefit is judged to outweigh the risks following consideration of other suitable treatment options.

If you become pregnant while taking Phenobarb, call your doctor.

Tell your doctor if you are breastfeeding or plan to breastfeed. Breast feeding is not recommended while taking this medicine as it can affect your baby.

Use in the elderly

Elderly patients are more likely to have less effective kidney or liver function due to age. This may increase the risk of side effects.

Tell your doctor if you are:

• allergic to any other medicines or any other substances, such as foods, preservatives or dyes
• have any other medical or health problems including:
  - blood pressure
  - heart problems
  - lung problems
  - hyperthyroidism (an overactive thyroid gland)
  - hypoadrenalism (borderline), an underfunctioning adrenal gland
  - a depressive illness
  - asthma
  - a heavy drinker
  - a drug dependency.

If you have not told your doctor about any of the above, tell them before you take any Phenobarb tablets.

Taking other medicines

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

Some medicines may interact with Phenobarb tablets. These include:

• other medications used to treat epilepsy
• anticoagulant medicines used to treat clots, e.g. warfarin
• painkillers, paracetamol and stronger narcotic agents
• antidepressants, medicines used to treat depression
• anti-arrhythmics, medicines used to treat irregular heartbeats e.g. quinidine, disopyramide
• antibiotics and antifungal agents, medicines used to treat infections
• including AIDS
• calcium channel blockers, medicines used to treat high blood pressure and angina
• antipsychotics, medicines used to treat certain mental and emotional conditions
• chemotherapy drugs, used to treat
• cancer
• corticosteroids, such as prednisolone, cortisone
• medicines used to treat heart failure e.g. digoxin
• oral contraceptives
• immunosuppressive medicines, used to lower your body's resistance to disease e.g. ciclosporin, tacrolimus
• medicines used to stop you from feeling pain, e.g. anaesthetic agents
• disulfiram, a medicine used to treat alcoholism
• diuretics
• thyroid replacement therapy medications, e.g. levothyroxine
• urinary alkalinisers
• antihistamines, medicines used to prevent or relieve symptoms of allergy.
• theophylline, medicine used to treat asthma.
• beta-blockers e.g. propranolol, used to treat high blood pressure and heart conditions.

The above medicines may reduce the effectiveness of Phenobarb tablets, reduce their own effectiveness and/ or react with it resulting in untoward or sometimes dangerous side effects.

Your doctor or pharmacist has more information on medicines to be careful with or avoid while taking Phenobarb tablets.

How to take it

How much to take

Take your medicine as directed by your doctor.

The usual doses of Phenobarb tablets are:

Adults:

• Sedative dose
  1-4 tablets as a single daily dose or as 2 to 3 divided doses per day.
• Anticonvulsant dose
  2-8 tablets as a single daily dose or as 2 to 3 divided doses per day.

Children:

• Your doctor will advise you of the correct dose, depending on the weight of your child.

How to take it

Swallow the tablets whole with a glass of water.

How long to take it

Continue taking Phenobarb tablets as long as your doctor recommends to.

Do not stop taking Phenobarb tablets without checking with your doctor. Do not let yourself run out of medicine over the weekend or on holidays.

Stopping this medicine suddenly may cause unwanted effects or make your condition worse. Your doctor will slowly reduce your dose before you can stop taking it completely.

If you forget to take it

Take your dose as soon as you remember, and then go back to taking it as you would normally.

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

If you are unsure about whether to take your next dose, speak to your doctor or pharmacist.

Do not try to make up for missed doses by taking more than one dose at a time. This may increase the chance of you getting an unwanted effect.

If you take too much (overdose)

Immediately telephone your doctor or Poisons Information Centre (telephone 13 11 26) for advice, or go to Accident and Emergency at your nearest hospital, if you think that you or anyone else may have taken too much Phenobarb.

Do this even if there are no signs of discomfort or poisoning.

Also report any other medicine or alcohol (including any barbiturates or narcotics) which has been taken.

You may need urgent medical attention.

Symptoms of overdose include weakness, dizziness, lethargy, nausea, vomiting, sweating, underbreathing, impairment of consciousness, collapse of circulation, mental confusion and low blood pressure.

While you are taking it

Things you must do

Take Phenobarb tablets exactly as directed by your doctor.

Tell your doctor if you want to take oral contraceptives while taking Phenobarb tablets. You may need a higher dose of oral contraceptives than usual to prevent pregnancy, or you may need to consider other forms of contraception.

Tell your doctor if you become pregnant while you are taking Phenobarb tablets.

If you need any medical tests while you are taking Phenobarb tablets, tell your doctor as it may affect the results of some tests.

Always discuss with your doctor any problems or difficulties during or after taking this medicine.

Your doctor may want to take some tests from time to time to help prevent unwanted side effects.

Things you must not do

Do not take any other medicines while you are taking Phenobarb tablets without first telling your doctor.

Do not drive or operate machinery until you know how this medicine affects you. Phenobarb may cause dizziness in some people and therefore may affect alertness.

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

Things to be careful of

Be careful drinking alcohol while taking Phenobarb tablets. If you drink alcohol, it could make some of the unwanted side effects of this medicine worse.

Your doctor may suggest that you avoid alcohol completely or reduce the amount of alcohol you drink while you are taking Phenobarb tablets.

Some people may experience side effects such as nausea, vomiting, constipation, drowsiness and dizziness which may further affect the risk when driving or using dangerous machinery.

Side effects

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

All medicines have side effects. Sometimes they are serious, most of the time they are not. You may need medical treatment if you get some of the side effects.

Ask your doctor or pharmacist any questions you may have.

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

• rapid heartbeat
• nausea (feeling sick)
• constipation
• dizziness
• lethargy
• vomiting
• skin rashes
• sweating
• dry mouth
• confusion
• faintness
• irritability
• restlessness
• dependency (habit-forming)
• mood changes
• drowsiness
• hyperexcitability
• hangover
• sleep disturbances.

The above side effects are common.

Tell your doctor immediately or go to Accident and Emergency at your nearest hospital if you notice any of the following:

• sore throat
• fever
• easy or unusual bleeding or bruising under the skin
• nosebleed
• other signs of infection e.g. swollen glands, mouth ulcers
• sudden signs of allergy e.g. severe skin rash (Steven-Johnson syndrome, toxic epidermal necrolysis), itching, hives, blisters or peeling skin.

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

Tell your doctor immediately or go to the Accident and Emergency department of your nearest hospital if you have any thoughts of harming yourself or committing suicide.

Tell your doctor or pharmacist if you notice anything else that is making you feel unwell. Other side effects not listed above may occur in some patients.

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

After taking it

Storage

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.

Keep this medicine in a cool dry place, protected from light where the temperature stays below 25°C.

Do not store it or any other medicines 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.

Disposal

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

Product description

What it looks like

Phenobarb tablets are uncoated, white, round and scored. Available in bottles of 200 tablets.

Ingredients

Active ingredient:
Each Phenobarb tablet contains 30 mg Phenobarbital.

Inactive ingredients:

• lactose monohydrate
• acacia
• starch - wheat
• magnesium stearate.

Phenobarb tablets contain gluten and lactose monohydrate.

Phenobarb tablets do not contain sucrose, tartrazine or any other azo dyes.

Sponsor

Arrotex Pharmaceuticals Pty Ltd
15-17 Chapel Street
Cremorne VIC 3121
Australia

www.arrotex.com.au

Australian registration number: AUST R 19758

This leaflet was revised in August 2023.

Published by MIMS September 2023

1 Name of Medicine

Phenobarbital.

2 Qualitative and Quantitative Composition

Phenobarb tablets contain phenobarbital 30 mg.
Excipients with known effect. Gluten and lactose monohydrate.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Phenobarb tablets are white, round uncoated biconvex tablets with a scoreline on one side and plain on the other side.

4 Clinical Particulars

4.9 Overdose

Clinical features. Overdosage of barbiturates produces CNS depression ranging from sleep to profound coma to death; respiratory depression which may progress to Cheyne-Stokes respiration, central hypoventilation, and cyanosis; cold, clammy skin and/or hypothermia or later fever, areflexia, tachycardia, hypotension, and decreased urine formation. Pupils are usually slightly constricted but may be dilated in severe poisoning. Patients with severe overdosage often experience typical shock syndrome; apnea, circulatory collapse, respiratory arrest, and death may occur. Complications such as pneumonia, pulmonary oedema, or renal failure may also prove fatal. Other complications which may occur are congestive heart failure, cardiac arrhythmias, and urinary tract infections. Some patients have developed bullous cutaneous lesions which heal slowly.
Barbiturates decrease gut motility, which may lead to slow onset and worsening of symptoms or cyclical improvement and worsening of symptoms.
Treatment. Treatment of overdosage is mainly supportive including maintenance of an adequate airway and assisted respiration and oxygen administration if needed. Standard treatment for shock should be administered if necessary. Activated charcoal may reduce absorption of phenobarbital if given within one or two hours after ingestion. In patients who are not fully conscious or have impaired gag reflex, consideration should be given to administering activated charcoal via a nasogastric tube, once the airway is protected. Multiple-dose, nasogastric administration of activated charcoal has been used effectively to treat phenobarbital overdose; activated charcoal enhances the elimination of the drug and shortens the duration of coma. The patient's vital signs and fluid intake should be monitored closely. Analeptic drugs should not be administered because they may produce paroxysmal cerebral activity which may result in generalised seizures. In addition, it has been demonstrated that analeptics are incapable of stimulating respiration and exerting an arousal effect in patients with severe barbiturate poisoning and profound CNS depression. If renal function is normal, forced diuresis may be of benefit. In addition, alkalinisation of the urine increases renal excretion of phenobarbital. Peritoneal dialysis or haemodialysis may be useful in severe barbiturate intoxication and/or if the patient is anuric or in shock.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.3 Preclinical Safety Data

Published studies reported teratogenic effects (morphological defects) in rodents exposed to phenobarbital. Cleft palate is reported consistently in all preclinical studies, but other malformations are also reported (e.g. umbilical hernia, spina bifida, exencephaly, exomphalos plus fused ribs) in single studies or species. In addition, although data from the published studies are inconsistent, phenobarbital given to rats/mice during gestation or early postnatal period was associated with adverse neurodevelopment effects, including alterations in locomotor activity, cognition and learning patterns.
Genotoxicity. Genotoxicity studies for gene mutations and chromosome aberrations have given mixed results, however, tests for DNA damage or repair have been negative.
Carcinogenicity. Phenobarbital sodium is carcinogenic in mice and in rats after lifetime administration. In mice, it produced benign and malignant liver cell tumours; in rats, benign liver cell tumours were observed. Phenobarbital was negative in a 26 week bioassay in p53 heterozygous mice.
In a 29 year epidemiologic study of 9,136 patients who were treated on an anticonvulsant protocol that included phenobarbital, results indicated a higher than normal incidence of hepatic carcinoma. Previously, some of these patients had been treated with thorotrast, a drug known to produce hepatic carcinomas. When patients who had received thorotrast were excluded, there was a non-significant increase in the number of liver tumours, and, unlike the mouse liver tumours, were mostly associated with cirrhosis.

6 Pharmaceutical Particulars

6.7 Physicochemical Properties

Phenobarbital presents as colourless crystals or a white odourless crystalline powder. It may exhibit polymorphism. It is soluble 1 in 1000 of water and 1 in 10 of alcohol; sparingly soluble in chloroform; soluble in ether. A saturated solution in water has a pH of about 5.
Chemical structure. Phenobarbital has the following chemical structure:
https://stagingapi.mims.com/au/public/v2/images/fullchemgif/CSPHBARL.gif Its molecular formula is C₁₂H₁₂N₂O₃. The molecular weight is 232.2.
CAS number. CAS-50-06-6.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Only Medicine).

Summary Table of Changes

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