Quantitative Determination of Cannabinoid Receptor Antagonist Surinabant in Human Plasma by LC-UV and LC-ESI-MS/MS Methods

Abstract

Surinabant [5-(4-bromophenyl)-1-(2,4-dichlorophenyl)-4-ethyl-N-(1-piperidinyl)-1H-pyrazole-3-carboxamide] is a cannabinoid receptor type 1 antagonist which is believed to indirectly inhibit the dopamine-mediated reward system for food, alcohol and nicotine addiction. Currently, there is no analytical method reported for the determination of surinabant in biological matrices. In this work, a liquid chromatographic (LC) method with both ultraviolet (UV) and electrospray ionization tandem mass spectrometric (ESI-MS/MS) detection has been developed and validated for the quantitative measurement of surinabant in human plasma to support the clinical investigation of this new drug. The compound AM251 was used for internal calibration. A protein precipitation procedure was employed for plasma sample preparation. Chromatographic separation of surinabant and internal standard was carried out on a Waters YMC™ Pro C4 cartridge column using a mobile phase containing 99.9% CH₃CN/H₂O (50:50, v/v) and 0.1% HCOOH. The LC-UV detection was accomplished by monitoring the absorption at 258 nm, which had an LLOQ of 100 ng/mL and a calibration range of 100–1500 ng/mL for surinabant. The LC-ESI-MS/MS detection was achieved using positive multiple-reaction-monitoring (MRM) mode for surinabant (m/z 523 → 423) and the internal standard (m/z 555 → 455), which had an LLOQ of 5.00 ng/mL and a calibration curve of 5.00–1000 ng/mL.

Keywords:

• Cannabinoid-receptor antagonist
• Human plasma
• LC-ESI-MS/MS
• LC-UV
• Surinabant

Notes

All determinations were based on the mean value obtained from five separate samples by duplicate measurements at each concentration. The concentration of internal standard was fixed (250 ng/mL).