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Isonex 100mg Tablet

Written By Dr. Sakshi Jain, MS, BDS
Reviewed By Dr. Sachin Gupta, MD Pharmacology, MBBS
Last updated on 14 Apr 2026 | 04:21 PM (IST)
Isonex 100mg Tablet is an antibiotic used for the treatment and prevention of tuberculosis (TB) and inactive (latent) TB (a serious infection caused by bacteria that affects the lungs and in certain cases other parts of the body). It works by killing the bacteria that cause tuberculosis.
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General Information

Contains

Isoniazid (100mg)

Marketer

Pfizer Ltd

Storage

Store below 30°C
The content is shown in English
Isonex 100mg Tablet image
Isonex 100mg Tablet image

Product introduction

Isonex 100mg Tablet should be used in the dose and duration as advised by your doctor. It is to be taken on an empty stomach. Do not skip any doses and finish the full course of treatment even if you feel better. Stopping it early can result in treatment failure and increase the side effects too. Do not take a double dose to make up for a missed dose. Simply take the next dose as planned.

Some common side effects of this medicine include tingling and numbness of feet and hand (peripheral neuropathy). Inform your doctor if you notice signs of jaundice, i.e., yellowing of eyes or skin, dark urine, stomach pain, or joint pain. You may also develop hepatitis (viral infection of the liver) or increased liver enzymes as side effects of this medicine. Please consult your doctor, as these side effects require medical attention and need dose modification.

Your doctor may monitor your liver function while on treatment with this medicine. Avoid drinking alcohol as this may have additional adverse effects on the liver. Pregnant or breastfeeding women should consult their doctor before using this medicine.

Uses of Isonex Tablet

Benefits of Isonex Tablet

Tuberculosis (TB)
Isonex 100mg Tablet is used to treat tuberculosis, an infectious disease that mainly affects the lungs but can affect other parts of the body as well. It kills and stops the growth of infection causing bacteria and helps in treating the infection. Take it in the dose and duration advised by the doctor. Your symptoms may improve before the infection is completely cured. Do not stop taking it without consulting your doctor as doing so may cause the infection to return or worsen. Follow your doctor’s instructions carefully to get maximum benefit.

Side effects of Isonex Tablet

Most side effects do not require any medical attention and disappear as your body adjusts to the medicine. Consult your doctor if they persist or if you’re worried about them
Common side effects of Isonex
  • Peripheral neuropathy (tingling and numbness of feet and hand)
  • Hepatitis (viral infection of liver)
  • Skin rash
  • Lethargy
  • Increased liver enzymes

How to use Isonex Tablet

Take this medicine in the dose and duration as advised by your doctor. Swallow it as a whole. Do not chew, crush or break it. Isonex 100mg Tablet is to be taken on an empty stomach.
Avoid Isonex 100mg Tablet with tyramine-rich food such as cheese, smoked fish, meats and some types of beer.

How Isonex Tablet works

Isonex 100mg Tablet works by stopping the growth of tuberculosis-causing bacteria. It interferes with the formation of the bacterial cell wall, which is essential for the survival of the bacteria. As a result, the bacteria become weak and are unable to multiply, helping control and treat tuberculosis (TB).

Quick tips

  • Your doctor has prescribed Isonex 100mg Tablet to cure your infection and improve symptoms.
  • It is best taken on an empty stomach.
  • You must also take a vitamin B6 supplement while on Isonex 100mg Tablet.
  • Tell your doctor immediately if you experience vision changes, loss of appetite, tiredness, stomach pain, nausea or vomiting, yellow skin or eyes or dark-colored urine.

Safety advice

Alcohol

Alcohol

UNSAFE
Consumption of alcohol with Isonex 100mg Tablet may cause a disulfiram-like reaction, leading to symptoms such as flushing, increased heart rate, low blood pressure, nausea, lightheadedness, and severe headache.
Pregnancy

Pregnancy

CONSULT YOUR DOCTOR
The safety of Isonex 100mg Tablet during pregnancy has not been established. There are no adequate and well-controlled studies in pregnant women, and animal data on reproductive toxicity are insufficient. Your doctor will weigh the benefits and any potential risks before prescribing.
Breast feeding

Breast feeding

SAFE IF PRESCRIBED
Available human data suggest that the drug does not pass into breast milk in clinically significant amounts and is unlikely to harm the infant.
Driving

Driving

UNSAFE
Isonex 100mg Tablet may cause side effects that could affect your ability to drive.
Isonex 100mg Tablet can cause fits, mental health problems and optic neuritis (inflammation of the optic nerve that may cause loss of vision.) This may affect your driving ability.
Kidney

Kidney

SAFE IF PRESCRIBED
Isonex 100mg Tablet is safe to use in patients with kidney disease. No dose adjustment is recommended.
However, talk to your doctor if you have any underlying kidney disease.
Liver

Liver

CAUTION
Isonex 100mg Tablet should be used with caution in patients with liver disease. Dose adjustment may be needed.
Use of Isonex 100mg Tablet is not recommended in patients with severe liver disease.

Interaction with drugs

Taking Isonex with any of the following medicines can modify the effect of either of them and cause some undesirable side effects
Severe

Didanosine (Oral Route)

Do not consume Didanosine with Isoniazid.
Severe

Halothane (Inhalation Route)

Talk to your doctor if you notice any unusual symptoms. Isoniazid may fasten the elimination of Halothane leading to reduced efficacy.
Severe

Citalopram (Oral Route)

If concurrent use is essential, please consult your doctor. Factors such as old age, chronic heart issues, or low potassium levels may more frequently cause disturbance in heart rhythm, and your doctor may consider ECG monitoring in their presence. Isoniazid may raise blood levels of Citalopram.
Severe

Stavudine (Oral Route)

Do not consume Isoniazid with Stavudine.
Moderate

Gliclazide (Oral Route)

If concurrent use is essential, your doctor may monitor your treatment and adjust the doses as per the observations.

Frequently asked questions

Isonex 100mg Tablet is an antibiotic used in the prevention and treatment of tuberculosis or TB (a serious infection caused by bacteria that affects the lungs and in certain cases other parts of the body)
Isonex 100mg Tablet is a primary antibiotic used for treatment of tuberculosis. Do not confuse it with chemotherapy or chemo drugs used for the treatment of cancer
Isonex 100mg Tablet is a bacteriostatic antibiotic. It stops or suppresses growth of tuberculosis causing bacteria by interfering with the formation of protective outer covering (cell wall) which is essential for their growth
Yes. Isonex 100mg Tablet is safe if used at prescribed doses for the prescribed duration as advised by your doctor
Isonex 100mg Tablet has very weak inhibitory activity on enzymes monoamine oxidases (MAO); however it is not used as a monoamine oxidase inhibitor (MAOI)
No. The chemical structure and mechanism of action of Isonex 100mg Tablet is different from sulfa drugs
Isonex 100mg Tablet is an inhibitor (decreases activity) of an important liver enzyme system that is responsible for the final processing and elimination of several drugs from the body
There no known serious drug interactions of isoniazid with ibuprofen, paracetamol (trade name: Tylenol), naproxen (trade name: Aleve), amoxicillin or any active drug present in Nyquil or Mucinex. Please inform your doctor about all the medication you are currently taking to avoid interactions that may reduce effectiveness of any treatment or aggravate side effects
Changes in body weight (gain/loss), hair loss, diarrhea or changes in menstruation are not among the known side effects of Isonex 100mg Tablet. You may experience few of these side effects while on multi drug (including Isonex 100mg Tablet) treatment for tuberculosis
You may experience unusual tiredness, constipation or acne while on treatment with Isonex 100mg Tablet. Please inform your doctor about all the medication you are currently taking to avoid interactions that may reduce effectiveness of any treatment or aggravate side effects
Isonex 100mg Tablet has no known interaction with commonly used oral contraceptives (birth control pills). However, multidrug treatment for tuberculosis contains active drug rifampin that decreases the effectiveness of oral contraceptives and hampers birth control.

Fact Box

Chemical Class

Pyridinecarboxylic acid derivative

Habit Forming

No

Therapeutic Class

ANTI INFECTIVES

Action Class

Mycolic acid inhibitors- INH

Related lab tests

Complete Blood Count

Erythrocyte Sedimentation Rate

Mycobacterium Tuberculosis DNA PCR - Qualitative

Peripheral Smear Examination

References

  1. Gumbo T. Chemotherapy of Tuberculosis, Mycobacterium Avium Complex Disease, and Leprosy. In: Brunton LL, Chabner BA, Knollmann BC, editors. Goodman & Gilman’s: The Pharmacological Basis of Therapeutics. 12th ed. New York, New York: McGraw-Hill Medical; 2011. pp. 1555-558.
  2. Chambers HF, Deck DH. Antimycobacterial Drugs. In: Katzung BG, Masters SB, Trevor AJ, editors. Basic and Clinical Pharmacology. 11th ed. New Delhi, India: Tata McGraw Hill Education Private Limited; 2009. pp. 824-25.
  3. Briggs GG, Freeman RK, editors. A Reference Guide to Fetal and Neonatal Risk: Drugs in Pregnancy and Lactation. 10th ed. Philadelphia, PA: Wolters Kluwer Health; 2015. pp. 741-42.
  4. Isoniazid. Nottingham, Nottinghamshire: Boots Contract Manufacturing; 2015. [Accessed 01 Apr. 2019] (online) Available from:
  5. Chaves RG, Lamounier JA. Breastfeeding and maternal medications. J Pediatr (Rio J). 2004;80(5 Suppl):S189-S198. [Accessed 29 Mar. 2019] (online) Available from:
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User feedback

Once A Day
87%
Twice A Day
10%
Twice A Week
3%
Tuberculosis (TB)
56%
Others
44%
Poor
50%
Excellent
33%
Average
17%
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Tata 1mg's sole intention is to ensure that its consumers get information that is expert-reviewed, accurate and trustworthy. However, the information contained herein should NOT be used as a substitute for the advice of a qualified physician. The information provided here is for informational purposes only. This may not cover everything about particular health conditions, lab tests, medicines, all possible side effects, drug interactions, warnings, alerts, etc. Please consult your doctor and discuss all your queries related to any disease or medicine. We intend to support, not replace, the doctor-patient relationship.

Marketer details

Name: Pfizer Ltd
Address: The Capital, 1802, 18th Floor , Plot No. C-70, ‘G’ Block , Bandra Kurla Complex, Bandra East , Mumbai – 400051.

Vendor Details

Country of origin: India

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