Isoniazid / rifampin Side Effects

Some side effects of isoniazid / rifampin may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to isoniazid / rifampin: oral capsule

If you experience any of the following serious side effects, stop taking isoniazid and rifampin and seek emergency medical attention or contact your doctor immediately:

• an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);

• excessive tiredness or weakness;

• nausea, vomiting, diarrhea, or loss of appetite;

• yellow skin or eyes;

• unusual bruising or bleeding;

• dark urine;

• little or no urine;

• numbness or tingling in your hands or feet;

• muscle or bone pain;

• seizures;

• blurred vision;

• fever, chills, or a sore throat;

• a headache;

• a rash or itching; or

• confusion or abnormal behavior.

Other, less serious side effects may be more likely to occur. Continue to take isoniazid and rifampin and talk to your doctor if you experience

• red-orange coloration of tears, sweat, saliva, urine, or feces; or

• mild tiredness or weakness.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

Applies to isoniazid / rifampin: oral capsule

General

The most common side effects reported with isoniazid were those affecting the nervous system and the liver.

Hepatic

Hepatic side effects have been reported frequently with isoniazid and have included elevated serum transaminases (SGOT, SGPT), bilirubinemia, bilirubinuria, jaundice, and occasionally severe and sometimes fatal hepatitis. Transient liver function test abnormalities (such as elevated serum bilirubin, alkaline phosphatase, serum transaminases) and, rarely, hepatitis or a shocklike syndrome (with liver involvement and abnormal liver function tests) have been reported with rifampin use. Rarely, fulminant hepatitis (i.e., acute hepatitis with hepatic encephalopathy) has been reported in patients treated with isoniazid-rifampin.

Prodromal symptoms are often observed with isoniazid-associated liver reactions and usually include anorexia, nausea, vomiting, fatigue, malaise, and weakness. Mild and transient elevation of serum transaminase levels occurs in 10% to 20% of patients taking isoniazid. The abnormality usually occurs in the first 4 to 6 months of treatment but can occur at any time during therapy. Enzyme levels usually return to normal even with treatment continuation; however, progressive liver damage occurs in some cases. Isoniazid should be discontinued at once if signs or symptoms indicative of liver damage are detected. The frequency of progressive liver damage increases with age. It is rare in patients under 20, but occurs in up to 2.3% of patients over 50 years of age.

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.

Nervous system side effects have been reported frequently with isoniazid and have included peripheral neuropathy and paresthesias. Convulsions and toxic encephalopathy have rarely been reported with standard isoniazid doses. Headache, drowsiness, fatigue, ataxia, dizziness, pain in extremities, and generalized numbness have been reported with rifampin use.

Renal

Renal hypersensitivity reactions usually occur during intermittent treatment or in patients resuming treatment following intentional or accidental interruption of the daily regimen. These reactions are reversible when rifampin is discontinued and appropriate therapy started.

Renal side effects associated with rifampin have included elevations in blood urea nitrogen. Hemolysis, hemoglobinuria, hematuria, interstitial nephritis, renal insufficiency, and acute renal failure have rarely been reported and are usually considered hypersensitivity reactions.

Hematologic

Thrombocytopenia has occurred with concomitant rifampin and ethambutol use according to a twice weekly dose schedule and in high doses.

Hematologic side effects associated with isoniazid have included agranulocytosis, anemia (hemolytic, sideroblastic, or aplastic), thrombocytopenia, and eosinophilia. Thrombocytopenia, leukopenia, hemolytic anemia, eosinophilia, decreased hemoglobin, and agranulocytosis (rare) have been reported with rifampin use.

Hypersensitivity

Hypersensitivity side effects associated with isoniazid have included fever, skin eruptions (morbilliform, maculopapular, purpuric, or exfoliative), lymphadenopathy, and vasculitis. Occasionally pruritus, urticaria, rash, pemphigoid reaction, eosinophilia, sore mouth, sore tongue, exudative conjunctivitis, and, rarely, renal hypersensitivity reactions have been reported with rifampin use.

Metabolic

Metabolic side effects associated with isoniazid have included pyridoxine deficiency, pellagra, hyperglycemia, and metabolic acidosis. Elevated serum uric acid has been reported with rifampin.

Gastrointestinal

Gastrointestinal side effects associated with isoniazid have included nausea, vomiting, and epigastric distress. Heartburn, epigastric distress, anorexia, nausea, vomiting, gas, cramps, diarrhea, and a red-orange discoloration of feces, saliva, and sputum have been reported with rifampin use.

Psychiatric

Psychiatric side effects associated with isoniazid are infrequent with standard doses and have included memory impairment and toxic psychosis. Inability to concentrate and mental confusion have been reported with rifampin use.

Ocular

Ocular side effects associated with isoniazid are infrequent with standard doses and have included optic neuritis and atrophy. Visual disturbances and a red-orange discoloration of tears have been reported with rifampin use.

Other

Other side effects associated with isoniazid have included systemic lupus erythematosus-like syndrome. Fever and a red-orange discoloration of sweat have been reported with rifampin use.

Musculoskeletal

Musculoskeletal side effects associated with isoniazid have included rheumatic syndrome. Muscular weakness has been reported with rifampin use.

Endocrine

Endocrine side effects associated with isoniazid have included gynecomastia.

Genitourinary

Genitourinary side effects associated with rifampin have included menstrual disturbances and a red-orange discoloration of urine.

Immunologic

Immunologic side effects associated with rifampin have included an immunosuppressive effect in some animal experiments; however, available human data indicate that this has no clinical significance.

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