Introduction: There is a large variation in cannabidiol (CBD) pharmacokinetics and little information on its bioavailability. This study aims to establish the CBD dose-exposure relationship and to evaluate the effects of dosage forms, food, and doses on CBD absorption.
Methods: Single-dose (range: 5-6000 mg) CBD plasma concentration-time profiles administered as oral solution (OS), oral capsule (OC), or oromucosal spray/drop (OM) from healthy volunteers were extracted from 15 published clinical studies. A dose-exposure proportionality assessment was performed, and a population-based meta-analysis of CBD pharmacokinetics and systemic bioavailability was conducted with a nonlinear mixed-effects modeling. A three-compartment model with a Weibull or zero-order absorption model was used to describe CBD disposition and absorption kinetics. Dosage form, food, and dose were assessed for covariation.
Results: Oral solution CBD exposures increased less than proportionally with doses of 750 mg or greater, and bioavailability (6.5% at 3000 mg) decreased with increasing dose. The bioavailability of OC (5.6%) and fed-state OM (6.2%) were similar, whereas it was lower in fasted-state OM (0.9%). The Weibull absorption model best described OS, OC, and fed-state OM profiles. The slowest absorption rate was observed in OS, resulting in a time of maximum concentration of 4.75 hours, followed by fed-state OM (3.13 hrs) and OC (2.1 hrs). The absorption kinetics of fasted-state OM was best described by a zero-order absorption for the duration of 1.71 hours.
Conclusion: The effects of doses, dosage forms, and feeding status on CBD pharmacokinetics were quantified and should be taken into consideration for dose optimization.
Keywords: absorption; bioavailability; cannabidiol; pharmacokinetics.
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