Coadministration of valerian (1000 mg nightly for 14 nights) with probes for CYP3A4 (alprazolam, 2 mg single dose) and CYP2D6 (dextromethorphan, 30 mg single dose) was studied in 12 subjects. Alprazolam Cmax and AUC increased by ~20%, but only the increase in Cmax was statistically significant. There was no significant effect of valerian on dextromethorphan metabolism. Typical doses of valerian are unlikely to produce clinically significant effects on drugs metabolised by CYP3A4 or CYP2D6.
Multiple night time doses of valerian (Valeriana officinalis) had minimal effects on CYP3A4 activity and no effect on CYP2D6 activity in healthy volunteers. Donovan JL, DeVane CL, Chavin KD, et al. Drug Met Dis, 2004, 32: 1333-1336.