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Nydrazid Side Effects

Generic Name: isoniazid

Note: This document contains side effect information about isoniazid. Some of the dosage forms listed on this page may not apply to the brand name Nydrazid.

For the Consumer

Applies to isoniazid: solution, tablet

Along with its needed effects, isoniazid (the active ingredient contained in Nydrazid) 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

  • Clumsiness or unsteadiness
  • dark urine
  • loss of appetite
  • nausea or vomiting
  • numbness, tingling, burning, or pain in hands and feet
  • unusual tiredness or weakness
  • yellow eyes or skin


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

  • 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


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


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]


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]


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


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


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


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


Frequency not reported: Psychosis, toxic psychosis[Ref]


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


Frequency not reported: Optic atrophy[Ref]


Frequency not reported: Bilirubinuria[Ref]


Frequency not reported: Vasculitis[Ref]


Frequency not reported: Gynecomastia[Ref]


Frequency not reported: Rheumatic syndrome[Ref]


Frequency not reported: Local irritation[Ref]


1. "Product Information. Nydrazid (isoniazid)" Apothecon Inc, Princeton, NJ.

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

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

4. Cerner Multum, Inc. "Australian Product Information." O 0

5. "Product Information. Isoniazid (isoniazid)." Barr Laboratories Inc, Pomona, NY.

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.