Isoniazid
Description
Isoniazid is an antibacterial medicine that is used to treat tuberculosis, a bacterial infection that affects the lungs. It is usually prescribed in combination with other medicines to prevent the spread of the infection. It prevents the bacteria from growing, thus it helps in treating the infection.
Isoniazid might cause some side effects like upset stomach, diarrhoea, fever, sore throat, etc., that subside with time. Inform your doctor if any of the side effects become severe or persist for a long time. Avoid consuming alcohol while you are on treatment with this medicine because it may cause liver damage.
Isoniazid is available on prescription in Tablet, and Injection form. The oral form of Isoniazid is recommended to be taken on an empty stomach. Take it at the same time every day to avoid missing a dose. Follow the dose and duration prescribed by your doctor and do not stop taking it without informing your doctor first. Abrupt discontinuation may cause the infection to reappear. It may take some time for the medication to show its effects. However, if you notice a worsening of your condition or if it does not improve, consult your doctor.
Isoniazid should be used with caution if you have liver and stomach/intestinal conditions. Inform your doctor about any other medications you are taking because some may interact with or be impacted by this medication. If you are pregnant or are breastfeeding, consult your doctor before taking this medicine. Isoniazid is not recommended in infants under three months of age.
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Side effects
Major & minor side effects for Isoniazid
- Dark urine
- Loss of appetite
- Nausea or Vomiting
- Unusual tiredness or weakness
- Tingling or numbness of the hands and feet
- Convulsions (seizures)
- Mental depression
- Joint pain
- Skin Rash
- Unusual bleeding or bruising
Uses of Isoniazid
What is it prescribed for?
- Tuberculosis
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Concerns
Commonly asked questions
- Onset of actionThe amount of time required for Isoniazid to show its action is not clinically established.
- Duration of effectThe amount of time for which Isoniazid remains active in your body is not clinically established.
- Safe with alcohol?Do not consume alcohol if you are on treatment with Isoniazid. Alcohol consumption may cause liver damage. Inform your doctor if you experience symptoms like unusual bleeding or bruising, joint pain or swelling, fever, chills, skin rash, severe abdominal pain, yellowing of the skin or eyes, etc.
- Is it habit forming?No habit-forming tendencies were reported for Isoniazid.
- Usage in pregnancy?Isoniazid is not recommended for use if you are pregnant. It may cause harm to your foetus; hence, consult your doctor before taking it.
- Usage while breast-feeding?Isoniazid passes into breast milk, therefore it is not recommended for use while breastfeeding.
Allergy
Avoid taking Isoniazid if you are allergic to it. Seek immediate medical attention if you notice any symptoms of allergic reactions such as a skin rash, itching/swelling (especially of your face/tongue/throat), severe dizziness, breathing difficulty, etc.
Severe liver impairment
Isoniazid is not recommeded if you have any liver conditions. This medicine is broken down in your liver, and improper liver function can lead to the accumulation of this medicine in your body. This may worsen your condition.
Warnings for special population
Pregnancy
Isoniazid is not recommended for use if you are pregnant. It may cause harm to your foetus; hence, consult your doctor before taking it.
Breast-feeding
Isoniazid passes into breast milk, therefore it is not recommended for use while breastfeeding.
General warnings
Use in children
Isoniazid is not recommended for use in infants of less than three months of age due to the lack of safety and efficacy of its use.
Elderly patients
Isoniazid should be used with caution in elderly individuals as they are at a higher risk of experiencing side effects associated with the medication."
Acidosis
Acidosis is a condition characterized by an increased level of acid in the body, which may occur as a side effect of taking Isoniazid. This can cause symptoms such as nausea and drowsiness, so it is important to avoid activities such as driving or operating heavy machines that requires mental alertness while taking this medication.
Missed Dose
Oral Formulations: Take the missed dose of Isoniazid as soon as possible. It is advisable to skip the missed dose if it is already time for your next scheduled dose. Do not double your dose to make up for the missed one.
Injection: Since Isoniazid is administered by a qualified healthcare professional in the clinical or hospital setting, the likelihood of missing a dose is very low. If you miss an appointment for receiving this medicine, contact your doctor immediately.
Overdose
Oral Formulations: Seek emergency medical treatment or contact your doctor in case of an overdose.
Injection: Since Isoniazid is administered in the hospital or clinical setting by a qualified healthcare professional, the likelihood of an overdose is very low. However, emergency medical treatment will be initiated by your doctor if an overdose is suspected.
All drugs interact differently for person to person. You should check all the possible interactions with your doctor before starting any medicine.
Interaction with Alcohol
Description
N/A
Instructions
Do not consume alcohol if you are on treatment with Isoniazid. Alcohol consumption may cause liver damage. Inform your doctor if you experience symptoms like unusual bleeding or bruising, joint pain or swelling, fever, chills, skin rash, severe abdominal pain, yellowing of the skin or eyes, etc.
Interaction with Medicine
Pimozide
Leflunomide
Halothane
Teriflunomide
Disease interactions
Peripheral Neuropathy
Peripheral neuropathy is damage to the peripheral nerves (nerves that are present outside the brain and spinal cord). This nerve damage mostly occurs in your feet and hands resulting in weakness, numbness, and pain. There are several causes that can lead to peripheral neuropathy such as diabetes, injuries, and infections. Isoniazid should be used with caution if you have peripheral neuropathy as it may worsen your condition.
Kidney dysfunction
Isoniazid should be used with caution if you have a history of kidney problems. This medicine is excreted through urine. Taking this medicine while you have kidney problems will lead to its accumulation. This can cause permanent damage to your kidneys and worsen your condition. Inform your doctor about your kidney problems.
Food interactions
Isoniazid should be taken on an empty stomach, at least one to two hours before or after a meal since food decreases the absorption of this medicine.
Lab interactions
Information not available.
Oral Formulations: Take Isoniazid exactly as prescribed by your doctor. Do not take in larger or smaller amounts than prescribed. Consult your doctor if you experience any undesirable effects. Ensure that the treatment course is completed. Do not stop the use of this medicine without consulting your doctor.
Injection: Isoniazid should be administered by a qualified healthcare professional in the clinical or hospital setting. Inform your doctor if you have a known history of allergy to this medicine. Inform your doctor of all your current medicines as well as your medical conditions before receiving this medicine. Ensure that the treatment course is completed; do not miss an appointment to receive an injection of this medicine.
Miscelleneous
How it works
Isoniazid prevents the formation of the protective layer of tuberculosis bacteria. Thus, helps to treat the infection.
Legal Status
Classification
Category
Hydrazide derivatives
Schedule
Schedule H
Drugs, H., 2021. Isoniazid: MedlinePlus Drug Information. [online] Medlineplus.gov. Available at: [Accessed 31 August 2021].
Pubchem.ncbi.nlm.nih.gov. 2021. Isoniazid. [online] Available at: [Accessed 31 August 2021].
Medicines.org.uk. 2021. [online] Available at: [Accessed 15 November 2021].
Dailymed.nlm.nih.gov. 2021. Isoniazid Tablets, USP. [online] Available at: [Accessed 15 November 2021].
Information on this page was last updated on 3 Mar 2023
Disclaimer
We’ve made all possible efforts to ensure that the information provided here is accurate, up-to-date and complete, however, it should not be treated as a substitute for professional medical advice, diagnosis or treatment. Practo only provides reference source for common information on medicines and does not guarantee its accuracy or exhaustiveness. The absence of a warning for any drug or combination thereof, should not be assumed to indicate that the drug or combination is safe, effective, or appropriate for any given patient. Practo does not assume any responsibility for any aspect of healthcare administered with the aid of information provided above. If you have any doubts about your medication then we strongly recommend that you consult with your doctor, nurse or healthcare provider. See detailed T&C here.