Changes in cortisol metabolism following rifampicin therapy.

A patient with Addison's disease required increased corticosteroid dosage whilst receiving rifampicin. The pharmacological half-life of cortisol was reduced, but returned to normal when rifampicin was stopped. Cortisolproduction rates in four patients with pulmonary tuberculosis rose during treatment with rifampicin, as did urinary D-glucaric-acid excretion, an index of liver microsomal-enzyme activity. The alteration of the corticosteroid requirement in the patient with Addison's disease and the elevation of the cortisol-production rates were attributed to increased cortisol catabolism following hepatic macrosomal-enzyme induction by rifampicin.