Determination of hydromorphone in human plasma by a sensitive RP-HPLC–ESI-MS method and its application to a clinical pharmacokinetic study in postoperative patients after low dose intravenous administration with infusion pump

Abstract

A sensitive reverse phase high performance liquid chromatography–electrospray ionization-mass spectrometry (RP-HPLC–ESI-MS) method has been developed and validated for the determination of hydromorphone in human plasma using naloxone as the internal standard (IS). After alkalization with saturated sodium bicarbonate, the plasma samples were extracted with ethyl acetate. Chromatographic separation was performed on a C18 column with the column temperature of 50 °C and a mobile phase of 5 mM ammonium acetate buffer containing 1% formic acid–methanol (88:12, v/v). Hydromorphone and the IS were detected by selected ion monitoring using the protonated molecules at m/ z 286.2 for hydromorphone and m/ z 328.2 for the IS. Calibration curve was linear over the range of 0.01–50 ng/mL. The lower limit of quantification was 0.01 ng/mL. The method was successfully applied to the pharmacokinetic study in postoperative patients after intravenous infusion of 1.5 mg hydromorphone hydrochloride. The obtained main pharmacokinetic parameters of hydromorphone in postoperative patients were as follows: the maximum hydromorphone plasma concentration ( C max) was (24.15 ± 12.51) ng/mL, the time to the C max was (10.0 ± 0.0) min, and the elimination half-life was (2.7 ± 0.8) h.