PDP-Isoniazid Adverse Reactions

Toxic effects are usually encountered only with higher doses of isoniazid, and their incidence is reportedly higher in slow inactivators. The incidence of adverse effects at a dose level of 10 mg/kg has been reported to be 15%.
CNS: peripheral neuropathy (occurs most often in the malnourished and is usually preceded by paresthesias of the feet and hands) is the most common (see PRECAUTIONS). Convulsions, toxic encephalopathy, optic neuritis and atrophy, and toxic psychosis may occur rarely.
Gastrointestinal: nausea, vomiting, epigastric distress, pancreatitis.
Hepatic: elevated serum transaminases (ALT, AST) and bilirubin concentrations (10 to 20%), hepatitis with or without jaundice. Isoniazid associated, occasionally severe and sometimes fatal hepatitis is generally considered an unpredictable hypersensitivity reaction (see WARNINGS).
Hematologic: agranulocytosis, hemolytic, sideroblastic or aplastic anemia; thrombocytopenia; eosinophilia.
Hypersensitivity: fever, skin eruptions (morbilliform, maculopapular, purpuric, or exfoliative), lymphadenopathy, vasculitis. Hypersensitivity reactions usually occur in the first 6 to 7 weeks of therapy (see PRECAUTIONS).
Metabolic and Endocrine: pyridoxine deficiency, pellagra, hyperglycemia, metabolic acidosis, gynecomastia.
Miscellaneous: rheumatic syndrome and systemic lupus erythematosus like syndrome.