Repeated administration of Sailuotong, a fixed combination of Panax ginseng, Ginkgo biloba, and Crocus sativus extracts for vascular dementia, alters CYP450 activities in rats.

Background: Sailuotong (SLT) is a standard Chinese preparation made from extracts of Panax ginseng (ginseng), Ginkgo biloba (ginkgo), and Crocus sativus (saffron). Preliminary clinical trials and animal experiments have demonstrated that SLT could improve cognition of vascular dementia (VD).

Purpose: To avoid incident drug-drug interaction which is easily encountered in patients of VD, the potential influence of SLT on main drug-metabolic cytochromes P450 enzymes (CYP450) was investigated.

Method: A "cocktail probes" approach was employed to evaluate the activities of CYP450. A rapid and selective analysis method was developed to examine 5 CYP probe drugs and their specific metabolites in plasma by using online SPE followed by a single LC-MS/MS run. After pretreatment for 2 weeks with SLT, ginseng, gingko, saffron or water (control), a cocktail solution containing caffeine, losartan, omeprazole, dextromethorphan and midazolam was given to rats orally. The plasma was obtained at different time intervals and then measured for the concentration of probes and their metabolites using developed SPE-LC-MS/MS method. Activity of five isozymes was estimated by comparing plasma pharmacokinetics of substrates and their metabolites (caffeine/paraxanthine for CYP1A2, losartan/E-3174 for CYP2C11, omeprazole/5-hydroxyl omeprazole for CYP2C6, dextromethorphan/dextrophan for CYP2D2 and midazolam/1-hydroxyl midazolam for CYP3A1/2) between control and drug treatment groups.

Result: Compared with control group, repeated administration of SLT induced CYP1A2 by enhancing AUC / AUC to144%. The influence is attributed to its herbal component of ginseng to a large extent. Meanwhile, metabolic ability towards losartan was significantly elevated in SLT and gingko group by 31% and 25% respectively, indicating weak induction of CYP2C11 in rats. The analysis on probes of omeprazole and dextromethorphan showed a lack of influence on CYP 2C6 and CYP2D2 in all treated groups. In terms of CYP3A1/2, SLT decreased AUC ratio of 1-hydroxyl midazolam to midazolam by 39% and extended the half-life of midazolam apparently. Besides, significantly decreased systematic exposure of midazolam suggested the inhibition on metabolism of CYP3A1/2 is likely secondary to the interaction on absorption at intestinal level. The inhibition of SLT on CYP3A was likely attributed to ginseng and gingko cooperatively.

Conclusion: Further observation on herb-drug interaction should be considered during clinical application of SLT.