Based on information derived from computers and clinical records obtained from general practitioners in the United Kingdom, we estimated the frequency of liver toxicity associated with two known hepatotoxins, chlorpromazine and isoniazid. Among the cohort of 10,502 users of chlorpromazine, 14 had illnesses compatible with drug-induced liver disease, a frequency of 1.3/1000 users (95% Cl 0.8, 2.2). Four presumed cases of the disorder occurred among 921 users of isoniazid, for a frequency of 4/1000 users (95% Cl 1.7, 11.1). This study provides population-based quantification of the frequency of liver disorders associated with the use of these two agents.
