Consumer Medicine Information
What is in this leaflet
This leaflet answers some common questions about ISONIAZID tablets.
It does not contain all of the available information about ISONIAZID tablets. 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 ISONIAZID tablets against the benefits they expect it will have.
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 ISONIAZID is used for
The name of your medicine is ISONIAZID tablets which contains the active ingredient isoniazid.
Isoniazid belongs to a group of medicines called tuberculostatic agents. It acts by stopping the growth of the bacteria responsible for tuberculosis.
ISONIAZID is used to treat tuberculosis in combination with other antitubercular agents.
Ask your doctor if you have any questions about why ISONIAZID has been prescribed for you. Your doctor, however, may have prescribed it for another purpose.
ISONIAZID tablets are available only with a doctor’s prescription.
Before you take it
When you must not take it
Do not take ISONIAZID if:
- you are allergic to ISONIAZID tablets or any of their ingredients listed at the end of this leaflet.
Some of the symptoms of an allergic reaction to ISONIAZID may include red, itchy skin rashes, difficulty breathing, hay fever, swelling of the face or throat or faintness.
- you have had severe reactions to ISONIAZID, for example fever, chills or arthritis.
- you have previously experienced liver problems after taking ISONIAZID tablets or any other medicines.
- you have acute liver problems from any cause.
Do not use ISONIAZID tablets after the expiry date (EXP.) printed on the pack. If you take it after the expiry date has passed, it may have no effect at all, or worse, there may be an entirely unexpected effect.
Do not purchase or use ISONIAZID tablets if the packaging is damaged or shows signs of tampering.
Elderly patients and patients over 50 years old are more likely to develop hepatitis, a possible side effect of using ISONIAZID. Older patients should be closely monitored by their doctor whilst using this medication.
Before you start to take it
You must tell your doctor if you are:
- allergic to any other medicines or any foods, dyes or preservatives
- you have any other medical conditions/ health problems, including:
- lung disease
- kidney disease
- liver disease
- you are a heavy drinker
- you are pregnant, intend to become pregnant, are breast-feeding or plan to breastfeed
Your doctor or pharmacist will discuss the possible risks and benefits of using ISONIAZID during pregnancy and breast-feeding.
If you have not told your doctor about any of the above, tell them before you take any ISONIAZID 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 interfere with ISONIAZID tablets.
- phenytoin (a medicine used to treat epilepsy)
- carbamazepine (a medicine used to treat epilepsy)
- rifampicin (a medicine used to treat tuberculosis)
- paracetamol (a medicine used to treat pain relief)
The above medicines may either reduce the effectiveness of ISONIAZID tablets, reduce their own effectiveness and/or react with it resulting in untoward or sometimes dangerous side effects.
This list is not exhaustive. Your doctor or pharmacist has more information on medicines to be careful with or avoid while taking ISONIAZID tablets.
To ensure that the treatment of your condition is effective your doctor will prescribe other medications to be taken over the same time period as ISONIAZID.
If you have any concerns about the interaction of these drugs you should discuss them with your doctor or pharmacist.
How to take it
How much to take
The recommended doses of ISONIAZID tablets are:
Adults: 4 to 5 mg per kg of body weight in divided doses up to a maximum of 300 mg daily. In tuberculous meningitis up to 10 mg per kg of bodyweight may be given daily for the first 1 to 2 weeks of treatment.
Children: 5 to 20 mg per kg of bodyweight daily.
Your doctor will advise you of the correct dose, depending on your weight or the weight of your child.
How to take it
The tablets should be swallowed whole with a glass of water.
How long to take it
It is very important that you continue taking ISONIAZID tablets as long as prescribed by your doctor, even after your symptoms have disappeared. If you do not do this it is very likely that your illness will return.
The treatment of tuberculosis requires long term therapy due to the nature of the bacteria responsible for the illness.
Isoniazid is administered orally.
If symptoms persist, see your doctor.
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 have trouble remembering when to take your medicine, ask your pharmacist for some hints.
If you take too much (overdose)
Immediately telephone your doctor or Poisons Information Centre (telephone 13 11 26) for advice, or go to casualty at your nearest hospital, if you think that you or anyone else may have taken too much ISONIAZID. 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 dizziness, nausea, vomiting, sweating, mental confusion, visual disturbances and slurring of speech.
While you are taking it
Things you must do
Use ISONIAZID tablets exactly as directed or as your doctor has prescribed.
If you are about to be started on any new medicine tell your doctor and pharmacist that you are using ISONIAZID.
Tell your doctor or pharmacist immediately if you feel sick (nauseous), fatigue, tired or generally unwell or have a loss of appetite while taking ISONIAZID.
Tell your doctor if you notice any problems with your eyes while taking ISONIAZID or if you feel that ISONIAZID is not helping your condition.
If you have to have any urine tests tell your doctor you are using this medicine as isoniazid may affect the results of some laboratory tests.
See your doctor regularly. Your doctor needs to check your progress and see whether you need to keep taking ISONIAZID tablets.
Always discuss with your doctor any problems or difficulties during or after taking ISONIAZID tablets.
Things you must not do
Do not take any other medicines while you are taking ISONIAZID tablets without first telling your doctor.
Do not drive or operate machinery until you know how this medicine affects you. It may cause dizziness in some people and therefore may affect alertness.
Do not give this medicine to anyone else, even if his or her symptoms seem similar to yours.
Things to be careful of
Be careful drinking alcohol while taking ISONIAZID tablets. If you drink alcohol, it could make some of the unwanted side effects of ISONIAZID worse.
Your doctor may suggest that you avoid alcohol completely or reduce the amount of alcohol you drink while you are taking ISONIAZID tablets.
Some people may experience side effects such as nausea, vomiting, constipation, drowsiness, dizziness, which may further affect the risk when driving or using dangerous machinery.
Tell your doctor or pharmacist as soon as possible if you do not feel well while you are taking ISONIAZID tablets. This medicine help most people with medical conditions listed in the beginning of this leaflet, but it may have unwanted side effects in some people, especially in elderly patients or those with underlying disorders.
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.
Common side effects
Tell your doctor immediately if you notice any of the following and they worry you:
- jaundice (yellowing of skin)
- nausea (feeling sick)
- skin rashes
- pain in arms or legs.
Some people may get other side effects of ISONIAZID tablets.
Check with your doctor as soon as possible if you have any problems while taking ISONIAZID tablets even if you do not think the problems are connected with the medicine or are not listed in this leaflet.
After taking it
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 ISONIAZID tablets in a cool dry place where the temperature stays below 25°C and protect from light.
Do not store it, or any other medicines, in a bathroom or near a sink.
Do not leave it in the car or on windowsills. Heat and dampness can destroy some medicines.
Do not take ISONIAZID if the tablets do not look quite right.
Keep your tablets in the bottle they were provided in until it is time to take them.
If your doctor tells you to stop taking this medication or it has passed the expiry date, ask your pharmacist what to do with any tablets that are left over.
What it looks like
ISONIAZID tablets are white scored tablets and are available in bottles of 100 tablets.
Each ISONIAZID tablet contains 100 mg of isoniazid.
They also contain the following inactive ingredients:
- silica-colloidal anhydrous
- sodium starch glycollate
- calcium stearate
- propyl hydroxybenzoate
- sodium benzoate
ISONIAZID tablets contain gluten and lactose but do not contain sucrose.
Arrow Pharma Pty Ltd
15 – 17 Chapel Street
Cremorne Victoria 3121
Australian Registration Number: AUST R 13455.
This leaflet was revised in July 2018.
Published by MIMS September 2018