Isoniazid chemoprophylaxis. Association with detection and incidence of liver toxicity.

The hepatotoxicity of isoniazid was studied in a double blind fashion in 120 adult patients receiving the drug for chemoprophylaxis. The incidence of abnormal SGOT values was significantly higher in those on the drug, 18.3% having elevated values as compared to 6.7% of those on placebo during the three-month study period. There was no statistical difference in the frequency of symptoms suggestive of liver diseases between the isoniazid and placebo groups. Furthermore, there was no significant relationship between symptoms and elevated SGOTs. Therefore, symptomatology would not appear to be a sensitive method for detecting early isoniazid liver toxicity. From available evidence, biochemical monitoring would appear to detect liver toxicity at an earlier and more reversible stage.