Objective: This research aimed to determine rifampicin in dried blood spot of tuberculosis patients using cilostazol as internal standard by high performance liquid chromatography for supporting therapeutic drug monitoring. Method: Analytes were extracted by protein precipitation using methanolacetonitril (4:1). The analytical separation was performed on C-8 column (Waters, Sun fire™ 5 μm; 250 x 4.6 mm) with column temperature of 40°C. The mobile phase used was acetonitrile - methanol - ammnonium acetate buffer pH 4.5 (40:30:30 % v/v) with a flow rate of 0.5 mL/min; and detected at 261 nm. Results: The method had a chromatographic run time of 16 min and linear calibration curve over the range of 1-30 μg/mL with a correlation coefficient (r) of 0.998. The result of the analysis of rifampicin in 18 tuberculosis patients showed that the measured value of rifampicin was in the range of 1.26 to 18.33 μg/ml. Conclusion: Based on the result, the concentration of rifampicin in patients were varied. There were 7 of 18 patients which had concentration in therapeutic range, showing that the treatment is appropriate, while 11 of 18 patients had concentration below the therapeutic range showing that dose adjustment is needed.
Key words: Rifampicin, HPLC, Tuberculosis, Validation, Dried blood spot.