Phytochemical Comparison of Medicinal Cannabis Extracts and Study of Their CYP-Mediated Interactions with Coumarinic Oral Anticoagulants

Introduction: Treatment with cannabis extracts for a variety of diseases has gained popularity. However, differences in herb-drug interaction potential of extracts from different plant sources are poorly understood. In this study, we provide a characterization of cannabis extracts prepared from four cannabis chemotypes and an in vitro assessment of their Cytochrome P450 (CYP)-mediated herb-drug interaction profiles.

Methods: Plant extracts were either commercially obtained or prepared using ethanol as solvent, followed by overnight decarboxylation in a reflux condenser system. The extracts were characterized for their cannabinoid content using NMR and HPLC-PDA-ELSD-ESIMS. CYP inhibition studies with the cannabis extracts and pure cannabinoids (tetrahydrocannabinol [THC] and cannabidiol [CBD]) were performed using pooled, mixed gender human liver microsomes. Tolbutamide and testosterone were used as specific substrates to assess the inhibitory potential of the extracts on CYP2C9 and CYP3A4, and the coumarinic oral anticoagulants warfarin, phenprocoumon, and acenocoumarol were studied as model compounds since in vivo herb-drug interactions have previously been reported for this compound class.

Results: In accordance with the plant chemotypes, two extracts were rich in THC and CBD (at different proportions); one extract contained mostly CBD and the other mostly cannabigerol (CBG). Residual amounts of the corresponding acids were found in all extracts. The extracts with a single major cannabinoid (CBD or CBG) inhibited CYP2C9- and CYP3A4-mediated metabolism stronger than the extracts containing both major cannabinoids (THC and CBD). The inhibition of CYP3A4 and CYP2C9 by the extract containing mostly CBD was comparable to their inhibition by pure CBD. In contrast, the inhibitory potency of extracts containing both THC and CBD did not correspond to the combined inhibitory potency of pure THC and CBD. Although being structural analogs, the three coumarin derivatives displayed major differences in their herb-drug interaction profiles with the cannabis extracts and the pure cannabinoids.

Conclusion: Despite the fact that cannabinoids are the major components in ethanolic, decarboxylated cannabis extracts, it is difficult to foresee their herb-drug interaction profiles. Our in vitro data and the literature-based evidence on in vivo interactions indicate that cannabis extracts should be used cautiously when co-administered with drugs exhibiting a narrow therapeutic window, such as coumarinic anticoagulants, regardless of the cannabis chemotype used for extract preparation.