- In vitro activity of commercial valerian root extracts against human cytochrome P450 3A4. Lefebvre, T., Foster, B.C., Drouin, C.E., Krantis, A., Livesey, J.F., Jordan, S.A. Journal of pharmacy & pharmaceutical sciences [electronic resource] : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques. (2004)