A botanically authenticated and chemically standardized hop extract was tested for Phase I pharmacokinetic drug interactions. Sixteen peri- and postmenopausal women consumed the hop extract twice daily for 2 weeks, and the pharmacokinetics of tolbutamide, caffeine, dextromethorphan, and alprazolam were evaluated before and after supplementation as probe substrates for CYP2C9, CYP1A2, CYP2D6, and CYP3A4/5, respectively. AUCs were unaffected, except for alprazolam which decreased by 7.6% suggesting minor induction of CYP3A4/5. No enzyme inhibition was detected. According to FDA guidelines, this hop dietary supplement caused no clinically relevant pharmacokinetic interactions with respect to CYP2C9, CYP1A2, CYP2D6, or CYP3A4/5.

Hop extracts were examined both structurally and functionally and were found to induce the expression of drug metabolism and excretion proteins. mRNA levels for CYP3A4, CYP2B6 and MDR1 were increased in a concentration-dependent manner by activating PXR. The efficacy with which hops activated PXR was comparable to that of St John's wort.