Liquid chromatographic determination of rifampin in human plasma, bronchoalveolar lavage fluid, and alveolar cells

A technique is presented for the measurement of rifampin in humans by reversed-phase column chromatography and postcolumn photo irradiation. The assay employs diazepam as an internal standard and provides specific, rapid, and reliable determinations for drug concentration in plasma, bronchoalveolar lavage (BAL), and alveolar cells (AC). The preparation of plasma and AC samples utilizes a simple deproteinization step, whereas BAL supernatants require a solid-phase extraction. The assay produces sharp peaks with retention times of 6.2 and 15 min for rifampin and diazepam, respectively. The detection limits for rifampin were 0.5 μg/mL for plasma, 0.015 μg/mL for BAL supernatants, and 0.03 μg/mL for AC suspensions. The assay has excellent performance characteristics, making it suitable for pharmacological studies in humans, and it is being used to support a study of the intrapulmonary pharmacokinetics of rifampin.