A Robust LC-MS/MS Bioanalytical Strategy for Simultaneous Quantification of Tramadol HCl and Dexketoprofen Trometamol and Its Use in Pharmacokinetic Studies.

This study reports the first bioanalytical method for simultaneous estimation of Tramadol HCl and dexketoprofen trometamol in rat plasma using Tapentadol as an internal standard. A validated LC-MS/MS method was developed following USFDA guidelines. Analytes were extracted from plasma by protein precipitation technique using acetonitrile. Chromatographic separation was achieved on a Waters Symmetry Shield RP-18 column (250 × 4.6 mm, 5 μm) with an isocratic mobile phase of acetonitrile and 0.1% formic acid in HPLC grade water (30:70 v/v) at a flow rate of 1.0 mL/min, yielding a 7-min runtime. Detection was performed using electrospray ionization with ion transitions of m/z 222.3398 → 70.0307 for Tapentadol, m/z 264.4351 → 96.4527 for Tramadol HCl, and m/z 376.4239 → 100.4520 for dexketoprofen trometamol. The method showed good accuracy, with mean recoveries of 92.79%-98.15% for Tramadol HCl and 91.78%-98.37% for dexketoprofen trometamol. Excellent linearity was obtained, with r2 values of 0.99983 (22.5-900 ng/mL) and 0.99963 (7.5-300 ng/mL), respectively. All validation parameters met acceptable criteria. The method is suitable for evaluating pharmacokinetic parameters that indicate drug efficacy and safety.