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Isoniazid Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP
Isoniazid is an antibiotic used to treat and to prevent tuberculosis (TB). Isoniazid is available in generic form. Common side effects of isoniazid include nausea, vomiting, or stomach upset. Contact your doctor if you experience serious side effects of isoniazid including an allergic reaction, unusual weakness or fatigue, yellow skin or eyes, dark urine, numbness or tingling in your hands or feet, seizures, or confusion or abnormal behavior.
The usual adult dose of Isoniazid is 5 mg/kg up to 300 mg daily in a single dose; or 15 mg/kg up to 900 mg/day, two or three times/week. Pediatric dose is 10-15 mg/kg up to 300 mg daily in a single dose; or 20-40 mg/kg up to 900 mg/day, two or three times/week. Isoniazid may interact with alcohol, antacids containing aluminum, ketoconazole, itraconazole, rifampin, rifabutin, disulfiram, warfarin, carbamazepine, cycloserine, phenytoin, ethotoin, mephenytoin, meperidine, benzodiazepines, theophylline, or ethionamide. Tell your doctor all medications and supplements you use. During pregnancy, Isoniazid should be used only when prescribed. This product passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding.
Our Isoniazid Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Isoniazid in Detail - Patient Information: Side Effects
If you experience any of the following serious side effects, stop taking isoniazid and seek emergency medical attention or contact your doctor immediately:
- an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
- unusual weakness or fatigue;
- nausea, vomiting, or loss of appetite;
- abdominal pain;
- yellow skin or eyes;
- dark urine;
- numbness or tingling in your hands or feet;
- blurred vision; or
- confusion or abnormal behavior.
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. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Isoniazid (Isoniazid)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Isoniazid FDA Prescribing Information: Side Effects
The most frequent reactions are those affecting the nervous system and the liver.
Nervous System Reactions: Peripheral neuropathy is the most common toxic effect. It is dose-related, occurs most often in the malnourished and in those predisposed to neuritis (e.g., alcoholics and diabetics), and is usually preceded by paresthesias of the feet and hands. The incidence is higher in "slow inactivators".
Hepatic Reactions: See BOXED WARNING. Elevated serum transaminase (SGOT; SGPT), bilirubinemia, bilirubinuria, jaundice, and occasionally severe and sometimes fatal hepatitis. The common prodromal symptoms of hepatitis are anorexia, nausea, vomiting, fatigue, malaise, and weakness. Mild hepatic dysfunction, evidenced by mild and transient elevation of serum transaminase levels occurs in 10 to 20 percent of patients taking isoniazid. This abnormality usually appears in the first 1 to 3 months of treatment but can occur at any time during therapy. In most instances, enzyme levels return to normal, and generally, there is no necessity to discontinue medication during the period of mild serum transaminase elevation. In occasional instances, progressive liver damage occurs, with accompanying symptoms. If the SGOT value exceeds three to five times the upper limit of normal, discontinuation of the isoniazid should be strongly considered. The frequency of progressive liver damage increases with age. It is rare in persons under 20, but occurs in up to 2.3 percent of those over 50 years of age.
Gastrointestinal Reactions: Nausea, vomiting, and epigastric distress.
Read the entire FDA prescribing information for Isoniazid (Isoniazid)
Additional Isoniazid Tablets Information
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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