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Active substance(s): ISONIAZID

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Package leaflet: Information for the user

If you have any further questions on the use of this medicine,
ask your doctor or pharmacist.

Isoniazid 100mg tablets


Read all of this leaflet carefully before you start taking this
medicine because it contains important information for
Always use this medicine exactly as described in this leaflet or
as your doctor, or pharmacist or nurse has told you.
! Keep this leaflet. You may need to read it again.
! Ask your pharmacist if you need more information or advice.
! If you get any side effects, talk to your doctor, or pharmacist
or nurse. This includes any possible side effects not listed in
this leaflet.
What is in this leaflet
1. What Isoniazid tablets are and what they are used for
2. What you need to know before you take Isoniazid tablets
3. How to take Isoniazid tablets
4. Possible side effects
5. How to store Isoniazid tablets
6. Contents of the pack and other information
Isoniazid is an antibiotic (antibacterial medicine) for treating
infections. It belongs to a group of antibiotics called
antituberculosis drugs and is used to treat and prevent
tuberculosis (TB), an infectious disease mainly affecting the
Do not take Isoniazid tablets:
! if you are allergic to Isoniazid or any of the other ingredients
of this medicine (listed in section 6).
! if you have ever suffered from liver damage caused by a
Warnings and precautions
Talk to your doctor or pharmacist before taking Isoniazid tablets
! if you have or have had problems with your liver or kidneys
! if you drink a lot of alcohol. It is also best to avoid alcohol
whilst you are taking this medicine
! if you are diabetic
! if you are pregnant, may become pregnant or are breast
! if you have the HIV infection
! if you have suffered mental disturbances (psychosis)
! if you have malnutrition
! if you have epilepsy or have ever had convulsions (fits)
! if you are presently taking itraconazole (to treat fungal
infections). It is not recommended to combine isoniazid and
Other medicines and Isoniazid tablets
Tell your doctor or pharmacist if you are taking, have recently
taken or might take any other medicines.
Isoniazid may interact with other medicines.
Please inform your doctor or pharmacist if:
! you are taking other medicine to treat tuberculosis (TB) (e.g.
para-aminosalicylic acid)
! you are taking disulfiram for alcohol dependence
! you are taking any medication for epilepsy (e.g.
carbamazepine, primidone, phenytoin)
! you are taking any other drugs for tuberculosis (e.g.
rifampicin, cycloserine)
! you are taking medication for HIV infection (e.g. stavudine)
! you are taking a vitamin B6 or B3 supplement
! you are taking medication for asthma or chronic obstructive
pulmonary disease (e.g. theophylline)
! you are taking medication for anxiety (e.g.
benzodiazepines; diazepam, triazolam, chlorzoxzone)
! you are taking medication for high blood pressure (e.g.
! you are taking drugs containing levodopa (used in the
treatment of Parkinson's disease)
! you are taking cycloserine (used to treat tuberculosis and
urinary tract infections)
! you are taking ketoconazole (used to treat fungal infections)
! you are taking zalcitabine (used in HIV infection)

Isoniazid tablets with food and drink
Isoniazid tablets should be taken preferably on an empty
stomach, i.e. at least 30 minutes before a meal or 2 hours after a
meal. Tablets must be swallowed whole and not chewed.
Isoniazid may interact with foods containing histamine (e.g.
tuna fish) or tyramine (e.g. cheese, red wine). These foods
should be avoided if you are receiving isoniazid.
Pregnancy, breast-feeding and fertility
If you are pregnant or breast-feeding, think you may be
pregnant or are planning to have a baby, ask your doctor or
pharmacist for advice before taking this medicine.
You may be given additional vitamin supplementation if you are
taking this medicine whilst pregnant.
You and your baby may be given additional vitamin
supplementation if you take this medicine while you are breastfeeding. Your baby should be checked by your doctor at regular
Driving and using machines
No studies on the effects on the ability to drive and use
machines have been performed. However, you may
experience side-effects such as dizziness and confusion during
treatment with isoniazid. Therefore, do not drive a car or
operate machinery until you know how isoniazid affects you.
Always take this medicine exactly as your doctor has told you.
Check with your doctor or pharmacist if you are not sure.
For adults, the recommended dose is dependent on
bodyweight. The maximum dose is three (3) of the 100 mg
tablets daily. For the treatment of tuberculous meningitis, a
higher dose may be given, particularly during the first 1 to 2
weeks of treatment.
For elderly patients, lower doses may be needed if the liver and
kidneys are not working so well.
Always take this medicine exactly as your doctor has told you.
Check with your doctor or pharmacist if you are not sure.
Your doctor will want to perform tests at regular intervals to
monitor your liver.
This will require you to give a blood sample.
Use in children
The dose for children is dependent on bodyweight, and can be
given in single or divided doses.
If you take more Isonazid tablets than you should
If you (or someone else) take too many, or you think a child may
have swallowed any tablets, contact your nearest hospital
casualty department or tell your doctor immediately. Take this
leaflet, and any tablets that you still have to show the doctor.
You may experience some of these side effects; Slurred
speech, high blood sugar, slow breathing, hallucinations,
dizziness, fits, or coma.
If you forget to take Isoniazid tablets
If you miss a dose, just carry on with the next one as normal. Do
not take a double dose to make up for a forgotten dose.
If you have forgotten several doses tell your doctor when you
have your next check-up or blood test. Occasionally people get
headache, sleeplessness, excessive dreaming, irritability or
nervousness if several doses are missed, or when the
treatment is stopped.
If you stop taking Isoniazid tablets
Keep taking the medicine for as long as your doctor has told
you, even if you are feeling better. If you stop the medicine too
soon, your infection may not be completely cured. You should
not stop treatment unless your doctor or health care provider
tells you to.

Like all medicines, this medicine can cause side effects,
although not everybody gets them.
Conditions you need to look out for:
! skin rash, breathing difficulties and possibly collapse
! severe skin reactions with ulcers or blisters, accompanied
by a general feeling of being unwell (Stevens- Johnson
! severe skin reaction with blisters that may also affect the
mouth and other parts of the body and may be accompanied
by fever, sore throat, headache and/or diarrhoea (erythema
! feeling tired, lose your appetite and feel sick and unwell
! yellow discoloration of your skin or eyes
Contact a doctor immediately if you get any of these
symptoms. Stop taking isoniazid Tablets.
Other side effects of Isoniazid may include;
Hypersensitivity and allergic reactions such as e.g. itching,
rash, nettle fever, sometimes with swelling in the skin,
mucous membranes and other parts of the body, vascular
inflammation, fever, joint pain.


Nervous system
Muscle weakness
Tingling or numbness in hands or feet
Loss of tendon reflexes
Overactive reflexes
Eye problems, double vision
Memory problems
Depression and paranoia
Feeling irritable
Feeling anxious
Unable to concentrate


Scaly skin sores
Sensitivity to sunlight
Inflammation of blood vessels (vasculitis), which may be
visible as red or purple
! Raised spots on the skin, but can affect other parts of the


High levels of cortisol in the blood (Cushing's syndrome)
Hormone imbalance in women with menstrual cycle
! Increase in size of breasts (in men)


Irregular heart beat
Changes in blood pressure, resulting in dizziness (vertigo)


Respiratory system


Connective tissue disorders such as Lupus syndrome
which can affect the skin and kidneys (symptoms may
include a butterfly shaped rash over the cheeks and nose,
tiredness, a high temperature, feeling or being sick, joint
pain and weight loss).


Although isoniazid usually improves people's mood, it can
cause mental disturbances. These side effects usually
disappear when you stop taking Isoniazid.
Abnormal antibodies in the blood (called ANA).
Serious side effects are more common in people over 35 or in
those who metabolise isoniazid more slowly. You may be given
a vitamin supplement to try and prevent some of these side
If you feel unwell in any way, tell your doctor as soon as you can.
Reporting of side effects
If you get any side effects, talk to your doctor or pharmacist.
This includes any possible side effects not listed in this leaflet.
You can also report side effects directly via the Yellow Card
Scheme at: By reporting side
effects you can help provide more information on the safety of
this medicine.
Keep this medicine out of the sight and reach of children. You
should keep your tablets below 25°C.
Do not use this medicine after the expiry date which is stated on
the carton after EXP. The expiry date refers to the last day of
that month.
Do not throw away any medicines via wastewater or household
waste. Ask your pharmacist how to throw away medicines you
no longer use. These measures will help protect the

! Increase in a certain type of white blood cells (leukocytes,
! Decrease in or complete lack of a certain type of white blood
cells (granulocytes)
! Reduction in the number of platelets
! Anaemia
! Blood clotting abnormalities
Digestive system
! Pancreatitis (the sudden onset of a severe pain in the centre
of your abdomen)
! Constipation
! Dry mouth
! Feeling sick/being sick
! Diarrhoea
! Increase in liver enzymes
! Inflammation of the liver (hepatitis), which may be severe.
Fatal cases have occurred
Metabolism and nutrition disorders
High blood sugar levels
Low blood sugar levels


Kidneys & Bladder
! Difficulty urinating

What Isoniazid tablets contains
! The active substance is Isoniazid. Each tablet contains 100
mg of Isoniazid.
! The other ingredients are: Calcium Hydrogen Phosphate,
Maize Starch (dried), Purified Talc, Colloidal Anhydrous
Silica, Magnesium Stearate.
What Isoniazid tablets look like and contents of the pack
Isoniazid tablets are white, circular, biconvex, uncoated tablets
having plain surface on both the sides.
Isoniazid tablets are available in Blister packs of 7, 10, 14, 20,
28, 30, 56, 60, 84, 90, 100 or 112.
Not all pack sizes may be marketed.
Marketing Authorisation Holder
Morningside Healthcare Ltd
115 Narborough Road, Leicester, LE3 0PA, UK
Morningside Pharmaceuticals Ltd
Pavilion Way, Loughborough, LE11 5GW, UK
This leaflet was last revised in February 2015.

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Source: Medicines and Healthcare Products Regulatory Agency

Disclaimer: Every effort has been made to ensure that the information provided here is accurate, up-to-date and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This information has been compiled for use by healthcare practitioners and consumers in the United States. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate that the drug or combination is safe, effective or appropriate for any given patient. If you have questions about the substances you are taking, check with your doctor, nurse or pharmacist.