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Isoniazid Side Effects

Medically reviewed by Drugs.com. Last updated on Apr 9, 2023.

Applies to isoniazid: solution, tablet.

Warning

Intramuscular route (Solution)

Severe and sometimes fatal hepatitis has been reported with isoniazid therapy and may occur even after many months of treatment. The risk for hepatitis increases with advancing age, concomitant alcohol use, chronic liver disease, and injection drug use. Patients given isoniazid should be carefully monitored and interviewed at monthly intervals. For persons 35 and older, in addition to monthly symptom reviews, hepatic enzymes (specifically, AST and ALT (formerly SGOT and SGPT, respectively) should be measured prior to starting isoniazid therapy and periodically throughout treatment. An increased risk of fatal hepatitis associated with isoniazid has been reported in women, particularly black and Hispanic women. The risk may also be increased during the post partum period. More careful monitoring should be considered in these groups, possibly including more frequent laboratory monitoring.

Oral route (Tablet; Syrup)

Severe and sometimes fatal hepatitis has been reported with isoniazid therapy and may occur even after many months of treatment. The risk for hepatitis increases with advancing age, concomitant alcohol use, chronic liver disease, and injection drug use. Patients given isoniazid should be carefully monitored and interviewed at monthly intervals. For persons 35 and older, in addition to monthly symptom reviews, hepatic enzymes (specifically, AST and ALT (formerly SGOT and SGPT, respectively) should be measured prior to starting isoniazid therapy and periodically throughout treatment. An increased risk of fatal hepatitis associated with isoniazid has been reported in women, particularly black and Hispanic women. The risk may also be increased during the post partum period. More careful monitoring should be considered in these groups, possibly including more frequent laboratory monitoring.

Serious side effects of Isoniazid

Along with its needed effects, isoniazid may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking isoniazid:

More common

Rare

Other side effects of Isoniazid

Some side effects of isoniazid may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

For injection form

Dark urine and yellowing of the eyes or skin (signs of liver problems) are more likely to occur in patients over 50 years of age.

For Healthcare Professionals

Applies to isoniazid: intramuscular solution, oral syrup, oral tablet.

General

The most commonly reported side effects included mild and transient elevation of serum transaminase levels, peripheral neuropathy, and hepatitis.[Ref]

Nervous system

Peripheral neuropathy usually occurred with doses over 5 mg/kg.[Ref]

Hepatic

Very common (10% or more): Mild and transient elevation of serum transaminase levels (up to 20%)

Uncommon (0.1% to 1%): Hepatitis

Frequency not reported: Abnormal liver function, bilirubinemia, jaundice, mild liver dysfunction, severe hepatitis/fatal hepatitis[Ref]

Mild and transient elevation in serum transaminases usually occurred in the first 1 to 6 months of treatment, but could occur at any time during treatment. Transaminase levels returned to normal with continued treatment in most cases.[Ref]

Nervous system

Common (1% to 10%): Peripheral neuropathy

Frequency not reported: Convulsions, memory impairment, optic neuritis, paresthesia of the feet/hands, toxic encephalopathy[Ref]

Dermatologic

Rare (0.01% to 0.1%): Eosinophilia systemic symptoms, toxic epidermal necrolysis

Frequency not reported: Allergic skin reaction, alopecia, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, erythema multiforme, exfoliative dermatitis, exfoliative skin eruptions, maculopapular skin eruptions, morbilliform skin eruptions, purpura, purpuric skin eruptions, rash, skin eruptions[Ref]

Hematologic

Frequency not reported: Agranulocytosis, anemia, aplastic anemia, eosinophilia, hemolytic anemia, lymphadenopathy, sideroblastic anemia, thrombocytopenia[Ref]

Metabolic

Frequency not reported: Anorexia, hyperglycemia, metabolic acidosis, pellagra, pyridoxine deficiency[Ref]

Gastrointestinal

Frequency not reported: Epigastric distress, nausea, pancreatitis, vomiting[Ref]

Other

Frequency not reported: Fatigue, fever, malaise, weakness[Ref]

Psychiatric

Frequency not reported: Psychosis, toxic psychosis[Ref]

Musculoskeletal

Frequency not reported: Lupoid syndrome, systemic lupus erythematosus-like syndrome[Ref]

Ocular

Frequency not reported: Optic atrophy[Ref]

Genitourinary

Frequency not reported: Bilirubinuria[Ref]

Cardiovascular

Frequency not reported: Vasculitis[Ref]

Endocrine

Frequency not reported: Gynecomastia[Ref]

Immunologic

Frequency not reported: Rheumatic syndrome[Ref]

Local

Frequency not reported: Local irritation[Ref]

References

1. Product Information. INH (isoniazid). Ciba Pharmaceuticals, Summit, NJ.

2. Product Information. Nydrazid (isoniazid). Apothecon Inc. 2001;PROD.

3. Cerner Multum, Inc. UK Summary of Product Characteristics.

4. Product Information. Isoniazid (isoniazid). Barr Laboratories Inc. 2006.

5. Cerner Multum, Inc. Australian Product Information.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer