Can Cannabinoids Precipitate UGT‐mediated Drug Interactions?

Abstract

Background: Cannabidiol (CBD) and tetrahydrocannabinol (THC) are cannabinoids used predominately for medicinal and recreational purposes, respectively. Because these cannabinoids are often co-consumed with conventional drugs, there is concern for deleterious cannabinoid-drug interactions. Both cannabinoids and their major circulating metabolites (7-OH CBD or 11-OH THC) are potent inhibitors of CYPs, but their potency to inhibit UGTs has not been investigated. Objective The objective of the study was to predict the potential for CBD and THC to precipitate UGT-mediated drug interactions using an IVIVE approach. The aims were to determine the following for CBD, THC, and their metabolites: 1) fraction unbound in incubations (fu,inc) containing recombinant UGT (rUGTs) and 0.2% BSA and 2) unbound UGT inhibitory potency (IC50,u). These data were used to predict the potential for interactions between each cannabinoid and UGT-metabolized drugs after typical doses used orally or by inhalation. Methods Fraction unbound (fu,inc) of CBD, THC, or metabolite in incubations containing rUGTs and 0.2% BSA was determined by ultracentrifugation. The inhibition extent (at 10 μM) or potency (IC50,u) of CBD, 7-OH CBD, 7-COOH CBD, THC, 11-OH THC, or 11-COOH THC towards the glucuronidation of estradiol (UGT1A1), chenodeoxycholic acid (UGT1A3), trifluoperazine (UGT1A4), 4-OH indole (UGT1A6), propofol (UGT1A9), gemfibrozil (UGT2B4), naloxone (UGT2B7), amitriptyline (UGT2B10), oxazepam (UGT2B15), or testosterone (UGT2B17) was determined using rUGTs. Estimated IC50,u and unbound hepatic inlet (oral dose) or systemic plasma (inhaled dose) concentrations were used to predict the potential for interactions between CBD (700 mg) or THC (20 mg) and drugs metabolized by UGT with fm values of 0.25, 0.5, or 0.75. Results fu,inc of CBD, 7-OH CBD, and THC was 0.05, 0.20, and 0.04, respectively. CBD, 7-OH CBD, THC, and 11-OH THC at 10 μM inhibited all UGTs tested (by 30-98%), whereas 7-COOH CBD inhibited only UGT2B7 (by 25%) and 11-COOH THC inhibited only UGT1A1, 1A4, and 1A9 (by 20-35%). IC50,u of CBD, 7-OH CBD, and THC against UGT1A9, 2B4, and 2B7 ranged from 0.002-0.02 μM, 0.6-1.6 μM, and 0.07-0.13 μM, respectively. IC50,u of CBD against UGT1A4, 1A6, 2B10, and 2B15 was < 1.3 μM. A mechanistic static model predicted strong in vivo interactions (AUC ratio > 3.3) between CBD and drugs extensively metabolized (fm = 0.75) by UGT1A9, 2B4, or 2B7. CBD was also predicted to result in moderate or weak interactions (1.3 ≥ AUC ratio ≤ 2.0) with drugs not extensively metabolized by these UGTs (fm = 0.25 or 0.5). In contrast, oral or inhaled THC was not predicted to precipitate UGT-mediated drug interactions (AUC ratio < 1.2). UGT inhibition by 7-OH CBD did not change the predicted potential of CBD-drug interactions. Conclusion This study is the first to determine the UGT inhibition potencies of cannabinoids. CBD was a potent inhibitor of UGT1A9, 2B4, and 2B7 and was predicted to interact with drugs metabolized by these UGTs. Further investigation via dynamic PBPK modeling and simulation and clinical evaluation is warranted to verify these predictions.