Skin deposition and permeation kinetics of cannabidiol and delta-9-tetrahydrocannabinol from cannabis extract containing gels

The study aimed to investigate the deposition and permeation characteristics of phytocannabinoids, namely delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), from cannabis extract containing gels. Cannabis extract with 26.3 % CBD and 28.4 % THC was used. The impact of permeation enhancers, namely propylene glycol, diethylene glycol monoethyl ether (DEGEE), ethanol (EtOH), and terpenes (eucalyptol and menthol), was examined. All cannabis extract gels had a pH range of 6.71-6.81 and a viscosity range of 456.6-4068.7 mPa & sdot;s. The phytocannabinoid release from the gels followed Zero-order kinetics with a rate of 14.5-25.7 mu g & sdot;h(-1) for CBD and 10.0-22.6 mu g & sdot;h(-1) for THC. A gel containing 12.5 % DEGEE and 12.5 % EtOH exhibited the highest release rate. The initial skin deposition followed Zero-order kinetics and reached a maximum level after 4 h. Permeation of phytocannabinoids closely followed Higuchi kinetics, with a rate of 0.14-54.21 mu g & sdot;h(-1/2) for CBD and 0.23-67.02 mu g & sdot;h(-1/2) for THC. A gel containing 25 % DEGEE and 25 % EtOH exhibited the highest apparent skin partition coefficient (K) value, resulting in the greatest phytocannabinoid deposition and permeation. Terpene introduction (5 %) significantly reduced the release rate, K value, and total skin absorption of phytocannabinoids. These findings offer useful insights into selecting the appropriate vehicle for cannabis extract topical products.