Isoniazid Induced Toxicities and Idiosyncratic Responses in Male Albino Wistar Rats

Isoniazid (INH) is an anti-tuberculosis drug administered over a long period. Upon metabolism in the liver, INH generates nitrogen-centered radicals, reacting with cellular macromolecules, and induces toxic and transformational changes in cells and tissues. Here we examined the side effects of long-term (chronic) administration of isoniazid (2.5 and 5mg/kg) once daily for 30, 60 and 90 days consecutively: on hepatic transaminases, histological changes in hepatocytes and induction of micronuclei in the bone marrow and possible genotoxicity in E. coli PQ37. In addition, blood glucose was monitored during the various treatment period. Biochemical analysis of hepatic transaminases (I³ -glutamyl-, alanine amino-, aspartate aminotransferases and alkaline phosphatase) in INH treated group was significantly (p 0.05) in GST in both treatment groups at day 60. There was also a significant increase ( p <0.05) in the activity of superoxide dismutase activity. Micronucleus analysis further revealed an induction of micronucleated polychromatic erythrocytes (mPCEs), which was significant ( p <0.05) for both treatment doses at days 30, 60 and 90 respectively. In addition, INH genotoxicity assessed by UMU chromotest indicated that the 5mg/kg dosage has an induction ratio above the genotoxicity threshold of 1.5 suggesting genotoxicity in E.coli PQ37. Taken together, INH treatment at both doses (2.5 and 5mg/kg body weight) was hepatotoxic and induced nephrotoxic damages, in addition to mutagenic effect which is more pronounced at 2.5mg/kg dose, thereby suggesting dose-dependent cellular and genetic toxicity.