Isoniazid Side Effects

Medically reviewed by Drugs.com. Last updated on May 18, 2024.

Applies to isoniazid: solution, tablet.

Precautions

It is very important that your doctor check your progress at regular visits. Also, check with your doctor immediately if blurred vision or loss of vision, with or without eye pain, occurs during treatment. Your doctor may want you to have your eyes checked by an ophthalmologist (eye doctor).

If your symptoms do not improve within 2 to 3 weeks, or if they become worse, check with your doctor.

Certain foods such as cheese (Swiss or Cheshire) or fish (tuna, skipjack, or Sardinella) may rarely cause reactions in some patients taking isoniazid. Check with your doctor if redness or itching of the skin, hot feeling, fast or pounding heartbeat, sweating, chills or clammy feeling, headache, or lightheadedness occurs while you are taking this medicine.

Liver problems may be more likely to occur if you drink alcoholic beverages regularly while you are taking this medicine. Also, the regular use of alcohol may keep this medicine from working properly. Therefore, you should strictly limit the amount of alcoholic beverages you drink while you are taking this medicine.

If this medicine causes you to feel very tired or very weak; or causes clumsiness; unsteadiness; a loss of appetite; nausea; numbness, tingling, burning, or pain in the hands and feet; or vomiting, check with your doctor immediately. These may be early warning signs of more serious liver or nerve problems that could develop later.

• For diabetic patients:
• This medicine may cause false test results with some urine sugar tests. Check with your doctor before changing your diet or the dosage of your diabetes medicine.

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:

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:

For injection form

• irritation at the place of injection

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 adverse events

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

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

See also:

Further information

Isoniazid side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer