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Active substance(s): ISONIAZID

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Package leaflet: Information for the user

4. Possible side effects

Isoniazid 100mg Tablets
Read all of this leaflet carefully before you start taking this
Isoniazid tablets with food and drink
medicine because it contains important information for
Isoniazid tablets should be taken preferably on an empty
stomach, i.e. at least 30 minutes before a meal or 2 hours after a
Keep this leaflet. You may need to read it again.
meal. Tablets must be swallowed whole and not chewed.
If you have any further questions, ask your doctor or
Isoniazid may interact with foods containing histamine (e.g.
tuna fish) or tyramine (e.g. cheese, red wine). These foods
This medicine has been prescribed for you only. Do not
should be avoided if you are taking Isoniazid tablets.
pass it on to others. It may harm them, even if their signs of
illness are the same as yours.
Pregnancy, breast-feeding and fertility
If you get any side effects, talk to your doctor or pharmacist.
If you are pregnant or breast-feeding, think you may be
This includes any possible side effects not listed in this
pregnant or are planning to have a baby, ask your doctor or
leaflet. See section 4.
pharmacist for advice before taking this medicine.
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
1. What Isoniazid tablets are and what they are used for
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

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 whilst 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.
3. How to take Isoniazid tablets

2. What you need to know before you take Isoniazid

Always take this medicine exactly as your doctor has told you.
Check with your doctor or pharmacist if you are not sure.

Do not take Isoniazid tablets:
if you are allergic to isoniazid or any of the other ingredients
For adults, the recommended dose is dependent on
of this medicine (listed in section 6),
bodyweight. The maximum dose is three (3) of the 100mg
if you have ever suffered from liver damage caused by a
tablets daily. For the treatment of tuberculous meningitis, a
higher dose may be given, particularly during the first 1 to 2
weeks of treatment.
Warnings and precautions
Talk to your doctor or pharmacist before taking Isoniazid
For elderly patients, lower doses may be needed if the liver and
kidneys are not working properly.
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 drinking
Your doctor will want to perform tests at regular intervals to
alcohol whilst you are taking this medicine,
monitor your liver. This will require you to give a blood sample.
if you are diabetic,
if you are pregnant, may become pregnant or are breast!
Use in children
The dose for children is dependent on bodyweight, and can be
if you have the HIV infection,
given in single or divided doses.
if you have suffered mental disturbances (psychosis),
if you have malnutrition,
If you take more Isonazid tablets than you should
if you have epilepsy or have ever had convulsions (fits),
If you (or someone else) take too many, or you think a child may
if you are presently taking itraconazole (to treat fungal
have swallowed any tablets, contact your nearest hospital
infections). It is not recommended to combine isoniazid and
casualty department or tell your doctor immediately. Take this
leaflet, and any tablets that you still have to show the doctor.
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.

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
Please inform your doctor or pharmacist if:
If you miss a dose, just carry on with the next one as normal. Do
you are taking another medicine to treat tuberculosis (TB)
not take a double dose to make up for a forgotten dose.
(e.g. para-aminosalicylic acid, rifampicin, cycloserine),
you are taking disulfiram for alcohol dependence,
If you have forgotten several doses tell your doctor when you
you are taking any medication for epilepsy (e.g.
have your next check-up or blood test. Occasionally people get
carbamazepine, primidone, phenytoin),
headache, sleeplessness, excessive dreaming, irritability or
you are taking medication for HIV infection (e.g. stavudine,
nervousness if several doses are missed, or when the
treatment is stopped.
you are taking a vitamin B6 or B3 supplement,
you are taking medication for asthma or chronic obstructive
If you stop taking Isoniazid tablets
pulmonary disease (e.g. theophylline),
Keep taking the medicine for as long as your doctor has told
you are taking medication for anxiety (e.g.
you, even if you are feeling better. If you stop the medicine too
benzodiazepines: diazepam, triazolam, chlorzoxzone),
soon, your infection may not be completely cured. You should
you are taking medication for high blood pressure (e.g.
not stop treatment unless your doctor or health care provider
tells you to.
you are taking drugs containing levodopa (used in the
treatment of Parkinson's disease),
If you have any further questions on the use of this medicine,
you are taking cycloserine (used to treat tuberculosis and
ask your doctor or pharmacist.
urinary tract infections),
you are taking ketoconazole (used to treat fungal

Irregular heartbeat,
Changes in blood pressure, resulting in dizziness (vertigo).

Like all medicines, this medicine can cause side effects,
although not everybody gets them.
Respiratory system
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
Connective tissue disorders such as Lupus syndrome
which can affect the skin and kidneys (symptoms may
severe skin reaction with blisters that may also affect the
include a butterfly shaped rash over the cheeks and nose,
mouth and other parts of the body and may be accompanied
tiredness, a high temperature, feeling or being sick, joint
by fever, sore throat, headache and/or diarrhoea (erythema
pain and weight loss).
Although isoniazid usually improves people's mood, it can
feeling tired, loss of appetite, feeling sick and unwell,
cause mental disturbances. These side effects usually
yellow discoloration of your skin or eyes.
disappear when you stop taking Isoniazid tablets.
Contact a doctor immediately if you get any of these
symptoms and Stop taking Isoniazid tablets.
Other side effects of Isoniazid tablets may include:
Hypersensitivity and allergic reactions such as itching, rash,
nettle fever (sometimes with swelling in the skin, mucous
membranes and other parts of the body), vascular
inflammation, fever, joint pain.

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.
Nervous system
You can also report side effects directly via the Yellow Card
Scheme at: By reporting side
Muscle weakness,
effects you can help provide more information on the safety of
Tingling or numbness in the hands or feet,
this medicine.
Loss of tendon reflexes,
Overactive reflexes,
5. How to store Isoniazid tablets
Eye problems, double vision,
Keep this medicine out of the sight and reach of children.
This medicinal product does not require any special storage
Memory problems,
Depression and paranoia,
Feeling irritable,
Do not use this medicine after the expiry date which is stated on
Feeling anxious,
the carton after EXP. The expiry date refers to the last day of
Unable to concentrate.
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
Scaly skin sores,
Sensitivity to sunlight,
Inflammation of blood vessels (vasculitis), which may be
6. Contents of the pack and other information
visible as red or purple raised spots on the skin, but can
affect other parts of the body.
What Isoniazid tablets contains

The active substance is isoniazid. Each tablet contains
100mg of isoniazid.
Increase in a certain type of white blood cells (leukocytes,
The other ingredients are: calcium hydrogen phosphate,
maize starch (dried), purified talc, colloidal anhydrous silica
Decrease in or complete lack of a certain type of white blood
and magnesium stearate.
cells (granulocytes),
Reduction in the number of platelets,
What Isoniazid tablets look like and contents of the pack
Isoniazid tablets are white, circular, biconvex uncoated tablets
Blood clotting abnormalities.
having plain surface on both the sides.
Digestive system
Isoniazid tablets are available in blister packs of 7, 10, 14, 20,
Pancreatitis (the sudden onset of a severe pain in the centre
28, 30, 56, 60, 84, 90, 100 or 112.
of your abdomen),
Not all pack sizes may be marketed.
Dry mouth,
Marketing Authorisation Holder
Feeling sick/being sick,
Morningside Healthcare Ltd
115 Narborough Road, Leicester, LE3 0PA, UK
Increase in liver enzymes,
Morningside Pharmaceuticals Ltd
Inflammation of the liver (hepatitis), which may be severe.
Pavilion Way, Loughborough, LE11 5GW, UK
Fatal cases have occurred.
This leaflet was last revised in April 2016.
Metabolism and nutrition disorders
High blood sugar levels,
Low blood sugar levels.
Kidneys & Bladder
Difficulty urinating.
High levels of cortisol in the blood (Cushing's syndrome),
Hormone imbalance in women with menstrual cycle
Increase in size of breasts (in men).

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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.