Explanation

Isoniazid is a medicine that is used to fight tuberculosis (TB).

What does isoniazid do?

Isoniazid works by killing the bacteria that cause the TB infection.

What does it look like?

Isoniazid comes as a white tablet that you swallow, or as a liquid in a small glass bottle that your doctor or a nurse dilutes and injects into one of your veins. If this is done slowly, it is called an infusion.

When do I have to take it?

You will probably need to take your isoniazid every day. You should take it on an empty stomach. This should be at least half an hour before you eat, or 2 hours after a meal.

But what if I don't feel like taking it?

It's really important that you take your isoniazid, even if you don't feel like it, or if you feel better. It will help fight off your TB. If you stop taking it, the infection may come back.

Don't stop taking your isoniazid, or change how much you are taking, without talking to your doctor first.

What should I do if I forget to take it or I take too much?

If you forget to take your isoniazid, you should take it as soon as you remember. If you end up missing a dose completely, don't take twice as much next time to make up for it - remember the three Ds: Don't Double Dose!

If you forget to take it a few times, you should tell your doctor. Forgetting to take your isoniazid can sometimes give you headaches, make you feel sleepy, make you dream more than usual or feel anxious or irritable.

If your doctor or nurse is giving you your isoniazid, they are likely to remember to give you your medicine. But, if you think that you may have missed a dose, ask them.

How much do I take?

This depends on how much you weigh. Your doctor will tell you how much isoniazid you should take, and how often you need to take it. You will probably need to take it every day.

If you are being given isoniazid as an infusion or injection by your doctor or nurse, then they will know how much to give you and when.

What are the most likely side effects I might get if I take Isoniazid?

Some of the more usual side effects you might get are:

Fever/high temperature

Feeling or being sick

Other tummy problems

Difficulty weeing or pooing

Rashes on your skin

Numb or tingling hands or feet

Dry mouth

Feeling dizzy

Seizures

Problems with your eyes

You may feel more tired or get ill more than usual because of problems with your blood cells

Breathing quickly or feeling confused

Feeling anxious

Making your chest area (breasts) grow

Kidney problems

If you notice these or any other side effects, tell your doctor or an adult who looks after you.

What other side effects might I get?

Isoniazid can cause liver problems. If you feel tired, generally unwell and sick, or notice that the whites of your eyes go a yellowish colour, tell your doctor or an adult who looks after you immediately.

Isoniazid can also cause changes to your mood, but this is very unusual. It usually improves your mood, but it can make you believe or think strange or unreal things. These changes usually go away after you stop taking it.

Is it safe for me to take it?

Before you are treated with isoniazid, tell your doctor about any other medical problems that you know you have. This is especially important if you:

Have liver problems

Know you are allergic to isoniazid

Have HIV or AIDS

Have diabetes

Are very underweight

Have other problems with how your body chemistry works

You may need to be treated with another medicine as well.

Is it ok for me to take isoniazid if I'm already taking other medicines?

You should tell your doctor about any other medicines that you are taking, or have taken, recently, including herbal medicines. It's especially important to mention if you are taking:

Any medicines for liver problems

Medicines that help you relax (called sedatives)

Any medicines for treating mood problems

Any medicines for treating fungal infections

Is there anything else I need to know about Isoniazid?

When you are taking isoniazid, your doctor will give you blood tests to check that your liver and/or blood cells blood cells are working ok.

What if I have any more questions?

If you have any other questions, you can ask your doctor, or chat to other people with TB in the Medikidz forums and virtual world, Mediland.