Serum concentrations of clarithromycin and rifampicin in pulmonary Mycobacterium avium complex disease: long-term changes due to drug interactions and their association with clinical outcomes.

Background: Concomitant use of clarithromycin (CAM) and rifampicin (RFP) for the treatment of pulmonary Mycobacterium avium complex (MAC) disease affects the systemic concentrations of both drugs due to CYP3A4-related interactions. To date, however, there has been no report that investigates the long-term relationship between the drug concentrations, CYP3A4 activity, and clinical outcomes. Our aim was to investigate the time course of the drug levels in long-term treatment of subjects with pulmonary MAC disease, and examine the correlation of these concentrations with CYP3A4 activity and clinical outcomes.