Sensitive and valid assay for reliable evaluation of drug interactions mediated by human organic anion transporter 1 and 3 using 5-carboxyfluorescein.

Drug interactions can induce significant clinical impacts, either by increasing adverse effects or by decreasing the therapeutic effect of drugs, and thus, need to be explored thoroughly. Clinically significant drug interactions can be induced by organic anion transporter 1 (OAT1) and OAT3 when concomitant medications competitively interact with the transporters. The purposes of this study were to develop and validate a sensitive and selective analytical method for 5-carboxyfluorescein (5-CF) and optimize the experimental conditions for interaction studies. An analytical method using high-performance liquid chromatography (HPLC) equipped with a fluorescence detector was validated for accuracy, precision, matrix effect, recovery, stability, dilutional integrity, and carry-over effect. In addition, the 5-CF concentration, incubation period, and washing conditions for interaction study were optimized. Using a valid analytical method and optimized conditions, we performed an interaction study for OAT1 and OAT3 using 26 test articles. Some of the test articles showed strong inhibitory potency for the transporters, with IC50 values close to or less than 10 μM. The valid analysis method and optimized systems developed in this study can be utilized to improve the predictability of drug interactions in humans and consequently aid in successful disease treatment by maintaining appropriate systemic exposures.