The pharmacokinetic study on compound diphenhydramine hydrochloride and caffeine in rats

Objective  To establish an assay method for diphenhydramine hydrochloride and caffeine in rat plasma by UPLC-MS/MS for pharmacokinetic study. Methods  The chromatographic separation was performed on an ACE 3 C18-PFP (3.0 mm×150 mm, 3 μm) by isocratic elution with the mobile phase of water containing 0.1% formic acid and acetonitrile (62:38, V/V). MS condition was optimized in the positive ion detection mode by multiple reaction monitoring (MRM), along with the Agilent JetStream electrospray source interface (AJS-ESI). The precursors to the product ion transitions were 256.2→167.0 (m/z) for diphenhydramine hydrochloride, 262.0→167.0 (m/z) for the internal standard (IS) diphenhydramine-D6, 195.0→138.0 (m/z) for caffeine and 204.0→116.2 (m/z) for the IS caffeine-D9. Results  The calibration curve was linear in the range of 1-1×103 ng/ml for diphenhydramine hydrochloride in rat plasma (r=0.999 6), and in the range of 15-1.5×105 ng/ml for caffeine in rat plasma, (r=0.999 9). The intra-day and inter-day precision and accuracy were good (RSD Conclusion  This method is accurate, rapid and sensitive. It can be used for the determination of diphenhydramine hydrochloride and caffeine in rat plasma collected for pharmacokinetic study. The results of pharmacokinetic studies in rats provide reliable data support for the clinical application of the compound preparation.