Results of an Exploratory Crossover Pharmacokinetic Study Evaluating a Natural Hemp Extract-Based Cosmetic Product: Comparison of Topical and Oral Routes of Administration

Hemp extracts are widely used in topical cosmetic products and dietary supplements, and some users have reported unexpected positive urine THC test results after use. This exploratory, randomized, open-label crossover study in 20 healthy adults compared systemic exposure to cannabinoids and urine THC test positivity following a single oral versus topical dose of a natural hemp extract-based cosmetic product, with pharmacokinetic parameters for cannabidiol and its metabolites calculated using Phoenix WinNonlin. Oral administration produced a much faster time to peak concentration and substantially higher systemic exposure to cannabidiol than topical use, and 38% of participants tested positive for urinary THC metabolite after the oral dose despite the product containing no detectable THC. Topical application resulted in low, often unquantifiable cannabinoid exposure and no positive urine tests. The findings highlight a route-dependent difference in systemic exposure and urine drug test outcomes that remains only partially explained by current understanding of CBD metabolism.