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IsonaRif Side Effects

Generic Name: isoniazid / rifampin

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

For the Consumer

Applies to isoniazid / rifampin: oral capsule, oral tablet

Along with its needed effects, isoniazid/rifampin 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 / rifampin:

More common
  • Clumsiness or unsteadiness
  • dark urine
  • loss of appetite
  • nausea and vomiting
  • numbness, tingling, burning, or pain in hands and feet
  • unusual tiredness or weakness
  • yellow eyes or skin
Less common Rare
  • Bloody or cloudy urine
  • blurred vision or loss of vision, with or without eye pain
  • convulsions (seizures)
  • depression
  • greatly decreased frequency of urination or amount of urine
  • mood or mental changes
  • sore throat
  • unusual bleeding or bruising

Some side effects of isoniazid / rifampin 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 Less common
  • Sore mouth or tongue

This medicine commonly causes reddish-orange to reddish-brown discoloration of urine, stool, saliva, sputum, sweat, and tears. This side effect does not usually require medical attention.

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

For Healthcare Professionals

Applies to isoniazid / rifampin: oral capsule


Doses greater than 600 mg of rifampin given once or twice weekly have resulted in a higher incidence of adverse reactions, including the "flu syndrome" (fever, chills, malaise); hematopoietic reactions (leukopenia, thrombocytopenia, acute hemolytic anemia); shortness of breath; shock; anaphylaxis; renal failure; and cutaneous, gastrointestinal, and hepatic reactions.[Ref]


Frequency not reported: Vasculitis

Frequency not reported: Flushing, decreased blood pressure[Ref]


Frequency not reported: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, Stevens-Johnson syndrome, Toxic Epidermal Necrolysis (TEN), rash

Frequency not reported: Acne, exfoliative dermatitis, pemphigus

Frequency not reported: Erythema multiforme, skin reaction, pruritus, pruritic rash, urticaria, allergic dermatitis, pemphigoid, sweat discoloration, cutaneous reactions[Ref]


Frequency not reported: Gynecomastia, hyperglycemia

Rare (less than 0.1%): Adrenal insufficiency
Frequency not reported: Menstrual disorder/disturbances[Ref]


Frequency not reported: Nausea, vomiting, epigastric distress, diarrhea

Frequency not reported: Constipation, dry mouth, pancreatitis

Frequency not reported: Gastrointestinal disorder, abdominal discomfort, heartburn, flatulence, cramps, pseudomembranous colitis, sore mouth, sore tongue[Ref]


Frequency not reported: Thrombocytopenia, eosinophilia, agranulocytosis, hemolytic anemia

Frequency not reported: Anemia, aplastic anemia, lymphadenopathy

Uncommon (0.1% to 1%): Leukopenia
Rare (less than 0.1%): Disseminated intravascular coagulation
Frequency not reported: Decreased hemoglobin[Ref]


Frequency not reported: Hepatitis, elevated serum transaminases (SGOT, SGPT), bilirubinemia, bilirubinuria, jaundice

Common (1% to 10%): Elevated alkaline phosphatase
Rare (less than 0.1%): Abnormal liver function, shock-like syndrome with hepatic involvement
Frequency not reported: Hyperbilirubinemia[Ref]


Rare (less than 0.1%): Anaphylaxis[Ref]


Frequency not reported: Pellagra, pyridoxine deficiency, metabolic acidosis

Frequency not reported: Decreased appetite, anorexia[Ref]


Frequency not reported: Systemic lupus erythematosus-like syndrome, rheumatic syndrome

Rare (less than 0.1%): Myopathy
Frequency not reported: Muscle weakness, bone pain[Ref]

Nervous system

Peripheral neuropathy associated with isoniazid is dose-dependent, most often occurs in malnourished patients and in patients predisposed to neuritis (such as alcoholics and diabetics), and generally follows paresthesias of the hands and feet. The rate is higher in slow acetylators.[Ref]

Common (1% to 10%): Peripheral neuropathy
Uncommon (0.1% to 1%): Convulsions, toxic encephalopathy, optic neuritis and atrophy, memory impairment
Frequency not reported: Vertigo, polyneuritis (presenting as paresthesia, muscle weakness, loss of tendon reflexes)

Frequency not reported: Headache, drowsiness, cerebral hemorrhage, ataxia, dizziness, inability to concentrate, muscular weakness, pains in extremities, generalized numbness[Ref]


Frequency not reported: Tear discoloration, visual disturbances, conjunctivitis[Ref]


Frequency not reported: Fever

Frequency not reported: Anti-nuclear antibodies

Frequency not reported: Influenza-like syndrome, post-partum hemorrhage, fetal-maternal hemorrhage, porphyria, edema, fatigue, facial edema, edema of the extremities, shock[Ref]


Frequency not reported: Toxic psychosis

Frequency not reported: Psychotic disorder/psychoses, mental confusion, behavioral changes[Ref]


Rare (less than 0.1%): Hemolysis, hemoglobinuria, hematuria, interstitial nephritis, acute tubular necrosis, renal insufficiency, acute renal failure
Frequency not reported: Acute kidney injury, chromaturia, increased blood creatinine, elevated BUN, elevated serum uric acid[Ref]


Frequency not reported: Dyspnea, wheezing, discolored sputum, shortness of breath[Ref]


1. "Product Information. Rifamate (isoniazid-rifampin)." Aventis Pharmaceuticals, Kansas City, MO.

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

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.