Examining the Systemic Bioavailability of Cannabidiol and Tetrahydrocannabinol from a Novel Transdermal Delivery System in Healthy Adults: A Single-Arm, Open-Label, Exploratory Study.

INTRODUCTION: Transdermal cannabinoids may provide better safety and bioavailability profiles compared with other routes of administration. This single-arm, open-label study investigated a novel topical transdermal delivery system on the pharmacokinetics of cannabidiol (CBD) and tetrahydrocannabinol (THC). METHODS: Participants were 39.5 ± 7.37 years old and healthy, based on a review by the Medical Director. Blood was collected pre-dose and 10, 20, 30, and 45 min, and 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, and 12 h after topical application of 100 mg CBD:100 mg THC. Psychoactive effects were assessed prior to each timepoint. Area-under-the-curve (AUC0-12 h), maximum concentration (Cmax), time to maximum concentration (Tmax), area-under-the-curve to infinity (AUCI), terminal elimination rate constant (λ), terminal half-life (t½), and absorption rate constant (ka) were measured individually for CBD and THC. Safety was assessed by clinical chemistry, hematology, and adverse events. RESULTS: AUC0-12 h for CBD and THC was 3329.8 ± 3252.1 and 2093.4 ± 2090.6 pg/mL/h, with Cmax of 576.52 ± 1016.18 and 346.57 ± 776.85 pg/mL, respectively. Tmax for CBD and THC was 8 h, ranging from 2.5 h to 12 h and 10 min to 12 h, respectively. AUCI for CBD and THC was 6609.2 ± 7056.4 and 3721.0 ± 3251.7 pg/mL/h, with t1/2 of 5.68 ± 1.5 and 5.38 ± 1.25 h, respectively. CBD was absorbed at a faster rate compared with THC (123.36 ± 530.97 versus 71.5 ± 1142.19 h-1) but with similar λ (0.12 ± 0.029 versus 0.13 ± 0.03 h-1). No psychoactive effects were reported. Transdermal cannabinoid delivery was safe and well tolerated in the population studied. CONCLUSION: To our knowledge, this is the first pharmacokinetic study in humans that demonstrated CBD and THC entering systemic circulation via transdermal administration . This study represents an important contribution to understanding the pharmacokinetics of transdermal cannabinoids. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier-NCT05121506 (November 16, 2021).