Article Figures & Data
Figures
- Fig. 1.
Workflow for reevaluating CYP–mediated drug interaction risk associated with kratom use using mitragynine as the marker constituent. Inhibition of a CYP in a concentration-dependent manner and by at least 50% at the highest tested concentration indicates mitragynine-mediated inhibition. A leftward shift of ≥1.5-fold in IC50 indicates potential TDI (Grimm et al., 2009). An IC50 value <20 µM indicates potential clinical relevance of CYP inhibition, determined relative to the highest mitragynine concentration quantified from autopsy blood samples.
- Fig. 2.
IC50 curves for mitragynine after preincubation with HLMs using the index reactions diclofenac 4′-hydroxylation (CYP2C9) (A), dextromethorphan O-demethylation (CYP2D6) (B), and midazolam 1′-hydroxylation (CYP3A) (C) and with HIMs using midazolam 1′-hydroxylation (D) in the presence and absence of NADPH. Mitragynine was tested from 0.015 to 100 µM. Symbols and error bars denote means and S.D., respectively, of triplicate incubations. Curves denote nonlinear least-squares regression of the data.
- Fig. 3.
Concentration-dependent inhibition of CYP2D6-mediated dextromethorphan O-demethylation by mitragynine (0.37–10 µM) in HLMs. (A) Dixon and (B) Michaelis-Menten plots of the data. Symbols denote individual data points of duplicate incubations. Curves denote nonlinear least-squares regression of the data using the competitive inhibition model.
- Fig. 4.
Concentration- and time-dependent inhibition of CYP3A-mediated midazolam 1′-hydroxylation by mitragynine using a nondilution (1.67–30 µM) method with HLMs (A) and HIMs (B) and a dilution method (3–60 µM) with HLMs (C). Upper panels show log-linear decline in CYP3A activity with time. Symbols denote individual data points of duplicate incubations. Lines denote linear regression of the initial monoexponential decline. Lower panels show replots of the rate constants against inhibitor concentration. Curves denote nonlinear least-squares regression of the data. Insets depict the Kitz-Wilson plot of the time-dependent inhibition observed for mitragynine.
- Fig. 5.
Speculated bioactivation mechanisms for mitragynine causing time-dependent inhibition of CYP3A activity (midazolam 1′-hydroxylation).
- Fig. 6.
Drug interaction risks predicted via mechanistic static models associated with kratom use for stimulant effects/lower dose range (1–5 g), intermediate dose range (5–8 g), and predominantly opioid-like effects/higher dose range (>8 g). An interaction risk (AUCR >1.25, dashed red line) via reversible inhibition of CYP2D6 (dextromethorphan O-demethylation activity) (A) and reversible (from previous reports, dashed black line) and time-dependent (from current work, solid black line) inhibition of CYP3A (midazolam 1′-hydroxylation activity) (B).
Tables
- TABLE 1
Major enzymes involved in the metabolism of opioids and/or other drugs detected in postmortem blood samples obtained from kratom-related death cases in Colorado (Gershman et al., 2019)
Case no. Blood Mitragynine Concentration (μM) Other Drugs Major Enzyme(s) References 1 Positivea Butyryl-fentanyl, oxycodone, etizolam, diphenhydramine, THC CYP3A, CYP2D6 Lalovic et al. (2004); Niwa et al. (2005); Kanamori et al. (2019) 2 Positive Oxycodone, fluoxetine, pseudoephedrine CYP3A, CYP2D6 Lalovic et al. (2004); LLerena et al. (2004) 3 0.04 Etizolam, 5-MeO-AMT CYP3A Niwa et al. (2005) 4 Positive Morphine, codeine UGT2B7, CYP3A, CYP2D6 Crews et al. (2014) 5 0.35 Oxycodone, tramadol, topiramate, diphenhydramine, zolpidem CYP3A, CYP2D6 Pichard et al. (1995); Miotto et al. (2017); Yamamoto et al. (2017) 6 5.3 Citalopram CYP3A, CYP2C19, CYP2D6 von Moltke et al. (2001) 7 3.5 Furanyl-fentanyl NA NA 8 2.5 Temazepam, olanzapine, sertraline, clonazepam CYP3A, CYP2C9, CYP2C19, CYP2D6, UGT2B7 Kobayashi et al. (1999); Urichuk et al. (2008); Tóth et al. (2016) 9 0.42 3,4-Dimethoxy-N-methylamphetamine NA NA 10 6.7 Etizolam, nordiazepam, mirtazapine CYP3A, CYP2D6, CYP1A2 Ono et al. (1996); Störmer et al. (2000); Niwa et al. (2005) 11 12 2,4,5-Trimethoxyamphetamine CYP2D6 Ewald and Maurer (2008) 12 0.62 Oxycodone CYP3A, CYP2D6 Lalovic et al. (2004) 13 1.9 Oxycodone, fentanyl, cocaine CYP3A, CYP2D6, esterases Kamendulis et al. (1996); Guitton et al. (1997); Kanamori et al. (2019) 14 Positive —b — — 15 Positive U-47700 NA NA - TABLE 2
IC50 for mitragynine against CYP2C9, CYP2D6, and CYP3A activity with and without NADPH, post–30-min preincubation
Values represent means ± S.E. of the estimates obtained via nonlinear least-squares regression.
Enzyme IC50 (µM) Fold Shift (−)-NADPH (+)-NADPH CYP2C9 39.7 ± 4.7 40.0 ± 3.2 1.0 CYP2D6 0.67 ± 0.05 0.76 ± 0.11 0.9 CYP3A (HLMs) 18.9 ± 1.8 2.6 ± 0.3 7.3 CYP3A (HIMs) 21.9 ± 2.7 3.2 ± 0.3 6.8 - TABLE 3
Prediction of CYP3A-mediated kratom-drug interactions via a mechanistic static model
The object drugs were selected to encompass a wide range of Fg and fm values with minimal influence of transporters.
Victim Drug Therapeutic Drug Class Fg (Galetin et al., 2008) fm (Shou et al., 2008) AUCR Alfentanil Opioid, analgesic 0.6 0.87 4.26 Alprazolam Anxiolytic 0.94 0.8 2.43 Buspirone Anxiolytic 0.21 0.95 14.04 Cyclosporine Immunosuppressant 0.44 0.71 4.5 Felodipine Antianginal 0.45 0.81a 5.12 Nifedipine Antianginal 0.78 0.74 2.66 Quetiapine Antipsychotic 0.99b 0.84 2.46 Quinidine Antiarrhythmic 0.9 0.76 2.38 Trazodone Antidepressant 0.83 0.35c 1.60 Triazolam Hypnotic 0.75 0.92 3.76 Zolpidem Hypnotic 0.79 0.26 1.55 a Yadav et al. (2018).
b Mano et al. (2015).
c Mao et al. (2011).
Data Supplement
- Supplemental Data -
Supplementary Figure 1 - Inhibitory effects of kratom extracts (coded K-50, K-51, and K-52) and mitragynine on
cytochrome P450 (CYP) 2C9 (diclofenac 4′-hydroxylation) (A), CYP2D6 (dextromethorphan Odemethylation) (B), and CYP3A (midazolam 1′-hydroxylation) (C) activities in HLMs and CYP3A (D) activity in HIMs. Extracts were tested at 2, 10, and 20 µg/mL; mitragynine was tested at 1, 10, and 100 µM. Positive control inhibitors included sulfaphenazole (1 µM), quinidine (2 µM), and ketoconazole (0.1 µM) for CYP2C9, CYP2D6, and CYP3A, respectively.Supplementary Figure 2 - Representative Lineweaver–Burk plot showing inhibition of CYP2D6-mediated
dextromethorphan O-demethylation by mitragynine (0.37-10 µM) in HLMs.
- Supplemental Data -
In this issue
Refined Prediction of Potential Kratom-Drug Interactions
