Abstract: AIM: To establish an HPLC-MS/MS assay to determine fentanyl in human plasma. METHODS: D-fentanyl was used as an interal standard. Human plasma samples were extracted by n-hexane.The separation was carried out on an Thermo Hypurity C₁₈ (150 mm×2.1 mm, 5 μm) column at 40 ℃.The mobile phase consisted of methanol-0.1% formic acid (85∶15, V/V) at a flow rate of 0.3 mL/min. Electrospray ionization (ESI) source was applied and operated in the positive ion mode. Quantitaion was performed using multiple reaction monitoring (MRM) of the m/z 337.1→188.1 for fentanyl , and m/z 341.9→187.9 for D-fentanyl. RESULTS: The liner calibration curves were obtained in the range of 19.53-5000 pg/mL for fentanyl.The lower limit of quantification was 19.53 pg/mL.The relative standard deviation of the intra-assay and inter-assay precision of variation was less than 5.16%.The extraction recovery for fentanyl was above 90%.To study the pharmacokinetics of two transdermal patches of fentanyl, preparations were given to 24 healthy volunteers, and the relative bioavailability of AUC_0-144 was (94.0±19.5)%. CONCLUSION: It is an accurate, sensitive and rapid method that can be applied to determine fentanyl in human plasma.Two preparations of fentanyl are bioequivalent.

Key words: Fentanyl, HPLC-MS/MS, Bioequivalence