Isoniazid for latent tuberculosis

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Isoniazid for latent tuberculosis

This leaflet is about the use of isoniazid for latent (hidden or dormant) tuberculosis (TB for short) infection. Your child will have to take this medicine for at least 3-6 months to cure their TB.

Information-Standard-logoThis leaflet has been written for parents and carers about how to use this medicine in children. Our information sometimes differs from that provided by the manufacturers, because their information is usually aimed at adult patients. Please read this leaflet carefully. Keep it somewhere safe so that you can read it again.

It is essential that your child takes all their medicines daily, as explained by the doctor, and continues until the doctor tells you to stop.

Name of drug

Isoniazid (EYE-soe-NYE-a-zid)

Why is it important for my child to take this medicine?

Your child is likely to be infected with the bacteria that can cause TB, but at the moment this is not making them ill (i.e. it is latent or hidden or dormant). It is important that your child takes isoniazid to stop them becoming ill from the active form of TB (TB disease). The bacteria that cause TB are hard to kill, and infected children are more likely to develop TB disease than infected adults, and are also more likely to become seriously unwell. Your child will have to take isoniazid for at least 3-6 months

If your child has a problem with their liver, it is important to talk about this with your doctor before they prescribe the medicine.

You must continue to give the medicine until your doctor tells you to stop. If you stop too soon, or your child does not take the medicine as your doctor has told you to, the bacteria may not be killed and TB disease may develop. It is also possible that the bacteria will become resistant to isoniazid, which means that it will no longer work. This may mean that other stronger drugs will have to be used, or that if TB disease does develop, it will be much harder to treat.

What is isoniazid available as?

  • Tablets: 50 mg, 100 mg; these contain lactose
  • Liquid medicine can be ordered specially from your pharmacist 

When should I give isoniazid?

Isoniazid is usually given once each day, this is usually in the morning.

Give the medicine at about the same time each day so that this becomes part of your child’s daily routine, which will help you to remember.

How much should I give?

Your doctor will work out the amount of isoniazid (the dose) that is right for your child. The dose will be shown on the medicine label.

It is important that you follow your doctor’s instructions about how much to give.

How should I give it?

You need to give isoniazid to your child when their stomach is empty. Give it 30 minutes before a meal or 2 hours after a meal.

TabletsTablets should be swallowed with a glass of water, milk or juice. Your child should not chew the tablets. You can crush the tablet and mix it with a small amount of soft food such as yogurt, honey or jam. Make sure your child swallows it straight away, without chewing.

Liquid-medicineLiquid medicine: Measure out the right amount using an oral syringe or medicine spoon. You can get these from your pharmacist. Do not use a kitchen teaspoon as it will not give the right amount.

When should the medicine start working?

The medicine will start working straight away, although you will not see any difference in your child because isoniazid is being given to prevent them becoming seriously unwell with TB disease. However, they must continue to take the medicine every day until the doctor tells you to stop treatment. This will be for at least 3-6 months.

What if my child is sick (vomits)?

  • If your child is sick less than 30 minutes after having a dose of isoniazid, give them the same dose again.
  • If your child is sick more than 30 minutes after having a dose of isoniazid, you do not need to give them another dose. Wait until the next normal dose.

If your child is sick again, seek advice from your GP, pharmacist, TB nurse or hospital. They will decide what to do based on your child’s condition and the specific medicine involved.

What if I forget to give it?

Give the missed dose when you remember during the day, as long as this is at least 12 hours before the next dose is due.

Never give a double dose of isoniazid.

What if I give too much? 

If you think you may have given your child too much isoniazid, contact your doctor, TB nurse or local NHS services (111 in England and Scotland; 0845 4647 in Wales). Have the medicine or packaging with you if you telephone for advice.

Are there any possible side-effects? 

We use medicines to make our children better, but sometimes they have other effects that we don’t want (side-effects).

Side-effects you must do something about

If your child has swelling of the face, lips or tongue, difficulty breathing or gets a rash, blisters in the mouth, itching or fever take them to your doctor or hospital straight away as they may be allergic to isoniazid.

If your child feels sick (nausea) or is sick (vomits) for more than 24 hours, or gets a yellowish tinge to the skin or whites of the eyes, contact your doctor straight away, as there may be a problem with your child’s liver. Do not give any more isoniazid.

If your child seems to be getting more infections than usual (e.g. bad colds, chest or skin infections, stomach upsets), or they seem to bruise more easily or bleeding doesn’t stop as quickly as you would expect, contact your doctor straight away, as there may be a problem with your child’s blood.

If your child has problems with their sight (vision), has difficulty telling colours apart or develops eye pain, contact your doctor straight away.

Other side-effects you need to know about

Your child may get the following symptoms when they first start taking isoniazid.

  • they may feel sick (nausea) or be sick (vomit). Giving the medicine with some food or milk may help. They may also get constipation (difficulty doing a poo) or have difficulty passing urine (doing a wee).
  • they may get tingling or numbness in the hands or feet and may feel dizzy or light-headed. Encourage them to stand up slowly and to sit or lie down if they feel dizzy or light-headed.
  • they may have a dry mouth. Eating citrus fruits (e.g. oranges) and taking sips of water may help.

These symptoms should wear off as your child’s body gets used to the medicine. If they are still a problem after a week or so, contact your doctor or TB nurse for advice:

  • If your child feels thirsty all the time and needs to pass urine (wee) very often, contact your doctor, as they may have high blood sugar.
  • Your child may have swelling in the breast area, or their breasts may increase in size. If this happens, contact your doctor. These changes will reverse when they stop taking the medicine.

There may, sometimes, be other side-effects that are not listed above. If you notice anything unusual and are concerned, contact your doctor. You can report any suspected side-effects to a UK safety scheme at http://yellowcard.mhra.gov.uk.

Can other medicines be given at the same time as isoniazid?

  • You can give your child medicines that contain paracetamol or ibuprofen, unless your doctor has told you not to.
  • Isoniazid should not be taken with many common medicines that you get on prescription. Tell your doctor about all medicines your child is taking before starting isoniazid.
  • Check with your doctor or pharmacist before giving any other medicines to your child. This includes herbal or complementary medicines.

Is there anything else I need to know about this medicine?

  • Your doctor or TB nurse will take blood samples before your child starts isoniazid and regularly while they are taking it. This is to make sure that their liver is working properly, and that isoniazid has not affected it.

Keep all your clinic appointments, as your doctor or TB nurse needs to check how your child is doing.

It is important that your child has their TB medicines every day.

  • There is a small risk that the oral contraceptive pill will not work properly during treatment with isoniazid, so your daughter should use other forms of contraception if she is sexually active, and for 4-8 weeks after finishing the course.

General advice about medicines

  • Give medicines at about the same times each day, to help you remember.
  • If you are not sure a medicine is working, contact your doctor but continue to give the medicine as usual in the meantime. Do not give extra doses, as you may do harm.
  • Only give this medicine to your child. Never give it to anyone else, even if their condition appears to be the same, as this could do harm. 

If you think someone else may have taken the medicine by accident, contact a doctor straight away.

  • Make sure that you always have enough medicine. Order a new prescription at least 2 weeks before you will run out.
  • Make sure that the medicine you have at home has not reached the ‘best before’ or ‘use by’ date on the packaging. Give old medicines to your pharmacist to dispose of.

Where should I keep this medicine?

  • Keep the medicine in a cupboard, away from heat and direct sunlight. It does not need to be kept in the fridge.
  • Make sure that children cannot see or reach it.
  • Keep the medicine in the container it came in.

Who to contact for more information 

Your child’s doctor, pharmacist or TB nurse will be able to give you more information about isoniazid and other medicines used to treat TB.

You can also get useful information from: 
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