Figure 8-4 Bimodal distribution of serum isoniazid concentrations in a large group of Finnish patients. More than 300 patients were given intravenous injections of 5 mg/kg of isoniazid. Serum drug concentrations were assayed at multiple times after injection. The distribution of serum concentrations of isoniazid is shown for 180 minutes after injection. The red histogram represents rapid inactivators, and the white histogram represents slow inactivators. (From Petri WA Jr: Antimicrobial agents: Drugs used in the chemotherapy of tuberculosis, Mycobacterium complex disease and leprosy. In Hardman JG, Limbird LE, Goodman GA [eds]: Goodman and Gillman's the Pharmacological Basis of Therapeutics, 10th ed. New York, McGraw-Hill, 2001.)