Simultaneous determination of a novel diphenylpiperazine calcium channel blocker and its four metabolites in rat liver microsomes by liquid chromatography tandem mass spectrometry.

Dipfluzine hydrochloride (Dip), a novel diphenylpiperazine calcium channel blocker, has revealed the characteristics of a promising candidate for the treatment of cerebral vascular diseases in preclinical studies. Our research identified and quantified Dip and its 4 metabolites (M1, M2, M4 and M5) in rat liver microsomes by liquid chromatography tandem mass spectrometry. The results showed that Dip was firstly metabolized to M1 and M5 by 1- and 4-dealkylation from a piperazine nitrogen, and then the latter was subsequently metabolized to M2 and M4. The concentrations of Dip, M1, M2 and M5 were 557.3 ± 26.3, 854.3 ± 46.0, 2796.7± 126.9, 2473.3 ± 82.6 and 4.0 ± 0.4, 2.4 ± 0.1, 318.2 ± 8.7 and 27.4 ± 1.5 ng/ml in male and female rats, respectively. M4 (404.2 ± 22.2 ng/ml) was detected only in males not in females, suggesting that there is gender difference in the metabolism of Dip.