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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 Rifamate.
Applies to isoniazid/rifampin: oral capsule
Oral route (Capsule)
Severe and sometimes fatal hepatitis has been reported with isoniazid therapy and may occur even after many months of treatment. The risk for hepatitis generally increases with advancing age and alcohol use. Monthly clinical evaluation and liver function tests should be performed. Instruct patients to report immediately any of the prodromal symptoms of hepatitis, such as fatigue, weakness, malaise, anorexia, nausea, or vomiting. If these symptoms appear or if signs suggestive of hepatic damage are detected, isoniazid should be discontinued promptly. If isoniazid must be reinstituted, it should be reinstituted only after symptoms and laboratory abnormalities have cleared. The drug should be restarted in very small and gradually increasing doses and should be withdrawn immediately if there is any indication of recurrent liver involvement. Treatment should be deferred in persons with acute hepatic diseases.
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:
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:
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.
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.
Frequency not reported: Vasculitis
Frequency not reported: Flushing, decreased blood pressure
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
Frequency not reported: Gynecomastia, hyperglycemia
Rare (less than 0.1%): Adrenal insufficiency
Frequency not reported: Menstrual disorder/disturbances
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
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
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
Rare (less than 0.1%): Anaphylaxis
Frequency not reported: Pellagra, pyridoxine deficiency, metabolic acidosis
Frequency not reported: Decreased appetite, anorexia
Frequency not reported: Systemic lupus erythematosus-like syndrome, rheumatic syndrome
Rare (less than 0.1%): Myopathy
Frequency not reported: Muscle weakness, bone pain
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.
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
Frequency not reported: Tear discoloration, visual disturbances, conjunctivitis
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
Frequency not reported: Toxic psychosis
Frequency not reported: Psychotic disorder/psychoses, mental confusion, behavioral changes
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
Frequency not reported: Dyspnea, wheezing, discolored sputum, shortness of breath