The significant inhibition on CYP3A caused by radix Aconiti single herb is not observed in the Wutou decoction: The necessity of combination therapy of radix Aconiti.

Ethnopharmacological Relevance: Wutou (WT, Radix Aconiti), the mother root of Aconitum carmichaelii Debx., is a famous Chinese herb against rheumatoid arthritis. In Chinese clinics, PWT is often prepared as a decoction in combination with other herbs, such as Wutou decoction (WTD). The present study aimed to compare the effects of PWT single herb and WTD on CYP3A activity ex vivo and in vivo.

Materials And Methods: In the ex vivo study, CYP3A activity was determined by using testosterone (Tes) as a specific probe. Levels of Tes and its metabolite 6β-hydroxytestosterone (6β-OH-Tes) were measured using a validated ultra-performance liquid chromatography (UPLC) method. CYP3A protein and mRNA levels were measured by using Western blot and real-time PCR, respectively. In the in vivo study, CYP3A activity was determined by using buspirone (BP) as a specific probe. The plasma concentrations of BP and its primary metabolites, namely, 1-(2-pyrimidinyl) piperazine (1-PP) and 6'-hydroxybuspirone (6'-OH-BP), were determined using a validated UPLC-tandem mass spectrometry (UPLC/MS/MS) method.

Results: Compared with the control group, the formation rates of 6β-OH-Tes from Tes ex vivo significantly decreased in groups treated with PWT at the tested doses, and this decrease was accompanied by a striking decrease in CYP3A protein and mRNA levels. However, a significant increase was observed in the ratios in the WTD groups compared with PWT single herb groups. In vivo, both formation ratios of 6'-OH-BP and 1-PP from BP showed no significant change in the WTD group.

Conclusions: PWT can significantly inhibit CYP3A activity ex vivo at the tested doses because of the down-regulation of CYP3A protein and mRNA expression levels. WTD can significantly reverse the inhibition caused by PWT. WTD also had no significant effect on CYP3A activity in vivo. Results implied that the use of PWT as a part of the WTD prescription rather than PWT single herb is more appropriate in clinics.