Development of a liquid chromatography-tandem mass spectrometry method for measuring plasma and uterine tissue levels of indomethacin in rabbits treated with indomethacin-medicated Cu-IUDs.

BACKGROUND

Some side effects of copper intrauterine devices (Cu-IUDs) including increased uterine bleeding, pelvic infections and pain have been reported. The presence of indomethacin in such devices was found to be effective in relieving the symptoms. The aim of this study was to develop and validate a rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for measuring plasma and uterine tissue levels of indomethacin in rabbits after insertion of indomethacin-medicated Cu-IUDs.

STUDY DESIGN

Indomethacin was extracted from rabbit plasma and uterine tissue by a simple protein precipitation using acetonitrile. Chromatographic separation was carried out on a Diamonsil C(18) column (150×4.6 mm ID, 5 μm) with an isocratic mobile phase consisting of methanol, acetonitrile, water and formic acid (45:45:10:0.5, v/v/v/v). Mass spectrometric detection was achieved by a triple-quadrupole mass spectrometer equipped with an atmospheric pressure chemical ionization interface operating in positive ionization mode. Quantitation was performed using selective reaction monitoring mode. The LC-MS/MS method was validated with respect to selectivity, linearity, precision, accuracy, extraction recovery and stability, and then applied to the in vivo studies of indomethacin in rabbits treated with indomethacin-medicated Cu-IUDs.

RESULTS

The linear calibration curves of indomethacin in plasma and uterine tissue were obtained over the concentration range of 2.0-400 ng/mL and 4.0-800 ng/mL, respectively. The intra- and interday precision was less than 9.5%, and the relative error was within ±5.3%. After insertion of indomethacin-medicated Cu-IUDs in rabbits, indomethacin was rapidly absorbed, and peak plasma levels were reached in approximately 1 h. A multiphasic elimination pattern was observed, which was a rapid decline in plasma concentration during the first 100 h followed by a very slow clearance phase. The uterine indomethacin levels were significantly higher than simultaneous plasma levels.

CONCLUSIONS

The developed method proved to be rapid and sensitive, and was successfully applied to investigate the absorption and uterine distribution of indomethacin in rabbits after insertion of indomethacin-medicated Cu-IUDs.