Isoniazid is used together with other medicines to treat a lung infection known as tuberculosis (TB).
It can also be given for the prevention of TB if you have been exposed to the TB bacteria through contact with another person who has TB.
Take Isoniazid exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
Isoniazid is best taken on an empty stomach 1 hour before or 2 hour after food. You may take it after meals if you experience any stomach discomfort.
Isoniazid must be taken at regular intervals. Continue to take this medicine even when you feel better. Do not stop taking it unless instructed by the doctor.
Do not skip any doses. You must complete the entire course of antibiotic. If you don't, the infection will not be properly controlled.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, you must inform your doctor and pharmacist.
Alert your doctor if you have liver disease as this medicine may not be suitable for you.
Do not take this medicine if you ever had an allergic reaction (breathlessness, rashes, swollen eyes) to Isoniazid.
Inform your doctor if you have kidney disease.
Let your doctor know if you are pregnant or breastfeeding.
What must I do to prevent spreading TB to other people?
TB is spread through the air, especially when you cough, sneeze or laugh.
You may still be able to infect others while undergoing treatment for TB. If your doctor has told you to stay at home so that you do not spread TB to other people, follow his instructions. You may need to sleep in a bedroom separate from your family members.
Always cover your mouth when you cough, sneeze or laugh.
If you use tissue paper, seal it in a plastic bag before you throw it away.
Isoniazid may cause dizziness and blurred vision. If affected, do not drive or take part in any activity in which you need to be alert.
Other side effects may include any of the following: loss of appetite, stomach pain, breast enlargement in men, vomiting and weakness.
This medicine will also cause the level of your red blood cells to drop. Red blood cells carry oxygen around your body. A fall in the level of red blood cells may make you feel tired and worn out.
If you develop rashes, breathlessness, swollen mouth or eyes, stop the medicine and inform your doctor quickly. These could be signs of an allergic reaction.
Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
- unusual bleeding or bruising
- confusion and hallucinations (seeing, hearing or feeling things that are not existent)
- yellowing of the skin or eyes
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Inform your doctor if you are taking any of these medicines:
- medicines for epilepsy (seizures or fits) e.g. carbamazepine, phenytoin,
- medicines to treat fungal infections e.g. ketoconazole
- medicines for asthma e.g. theophylline
This list does not include all medicines that may interact with Isoniazid.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements and medicines that you buy without a prescription.
Avoid alcohol and other drinks that contain tyramine such as red wine and beer. Avoid foods that are high in tyramine, such as cheese, sausages, soya beans, fava beans, broad beans and certain pickles such as sauerkraut. Ask your doctor about the types of food you should avoid.
Store in a cool, dry place away from the reach of children.
Medicines must not be used past the expiry date.