Urinary metabolic profile of isoniazid in patients who develop isoniazid-related liver damage.

The urinary metabolite profile of isoniazid has been studied in patients receiving the drug as therapy for tuberculosis and the profile in patients suffering liver damage due to isoniazid compared with that in control patients. There were no consistent differences between control patients and those suffering liver damage in the excretion of isoniazid metabolites. It may be that susceptibility to the hepatotoxicity of isoniazid is not due to metabolic differences, although a number of other possible explanations are discussed. It is not at present possible to predict which patients will be susceptible from metabolic studies.