Isoniazid

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About isoniazid

This belongs to the group of medicines known as antituberculous drugs.

Isoniazid is used alongside other drugs to treat and prevent tuberculosis (TB).

Isoniazid is available in tablet, oral liquid and injection form.

Before taking isoniazid

Before taking isoniazid make sure your doctor or pharmacist knows:

• if you are pregnant, trying for a baby or breast-feeding
• if you suffer from liver or kidney problems
• if you suffer from or have previously suffered from psychosis (mental illness)
• if you suffer from porphyria (a blood disorder), diabetes, epilepsy or circulatory problems
• if you have HIV
• if you are alcohol dependent (drink excessively)
• if you have ever had an allergic reaction to this or any other medicine
• if you are taking any other medicines, including those available to buy without a prescription, herbal or complementary medicines

How to take isoniazid

• Take your medication exactly as directed by your doctor.
• Always read the manufacturer's information leaflet, if possible, before beginning treatment.
• Do not stop taking isoniazid without speaking to your doctor first.
• Isoniazid must be taken on an empty stomach (half to one hour before food).
• Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of isoniazid contact your doctor or go to the accident and emergency department of your local hospital at once. Always take the container with you, if possible, even if empty.
• This medicine is for you. Never give it to others even if their condition appears to be the same as yours.

Getting the most from your treatment

• Before taking any 'over-the-counter' medicines, check with your pharmacist which medicines are safe for you to take alongside isoniazid.
• Isoniazid can cause a dry mouth. If you experience this, try chewing sugar-free gum, sucking sugar-free sweets or a piece of ice. Alternatively a saliva substitute is available to purchase from your pharmacist. If a dry mouth becomes too troublesome speak to your doctor.
• Isoniazid can cause constipation. Constipation can be eased by eating plenty of fibre, such as fruit, vegetables, potatoes or bran and by drinking plenty of water.

Can isoniazid cause problems?

Along with their useful effects, all medicines can cause unwanted side effects, which usually improve as your body adjusts to the new medicine. Speak with your pharmacist or doctor if any of the following side effects continue or become troublesome.

Feeling or being sick, constipation, dry mouth, eye pain or loss of vision, convulsions (fits), dizziness, skin rash, difficulty urinating (passing water) or enlargement of the breasts in men and women.

Important: If you experience jaundice (yellowing of the skin and whites of the eyes), malaise, (generally feeling unwell), severe nausea, vomiting, problems breathing or a rash, contact your doctor or go to the accident and emergency department of your local hospital at once.

If you experience any other worrying symptoms, which you think may be due to this medicine, discuss them with your doctor or pharmacist.

How to store isoniazid

• Keep all medicines out of the reach of children.
• Store in a cool, dry place, away from direct heat and light.
• Never keep out of date or unwanted medicines. Discard them safely out of the reach of children or take them to your local pharmacist who will dispose of them for you.

© EMIS and Cegedim Pharmacy Services Ltd 2005   Updated: 19/10/2005   

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