Topical application of THC containing products is not able to cause positive cannabinoid finding in blood or urine

•An excretion experiment of topical application of THC containing creames was conducted over the course of 3 days.•No positive findings on THC and its metabolites neither in blood nor in urine samples of the volunteers.•Analytical results of an accused could not be explained by topical application.

A male driver was checked during a traffic stop. A blood sample was collected 35 min later and contained 7.3 ng/mL THC, 3.5 ng/mL 11-hydroxy-THC and 44.6 ng/mL 11-nor-9-carboxy-THC. The subject claimed to have used two commercially produced products topically that contained 1.7 ng and 102 ng THC per mg, respectively. In an experiment, three volunteers (25, 26 and 34 years) applied both types of salves over a period of 3 days every 2-4 h. The application was extensive (50-100 cm2). Each volunteer applied the products to different parts of the body (neck, arm/leg and trunk, respectively). After the first application blood and urine samples of the participants were taken every 2-4 h until 15 h after the last application (overall n = 10 urine and n = 10 blood samples, respectively, for each participant). All of these blood and urine samples were tested negative for THC, 11-hydroxy-THC and 11-nor-9-carboxy-THC by a GC-MS method (LoD (THC) = 0.40 ng/mL; LoD (11-hydroxy-THC) = 0.28 ng/mL; LoD (THC-COOH) = 1.6 ng/mL;. LoD (THC-COOH in urine) = 1.2 ng/mL). According to our studies and further literature research on in vitro testing of transdermal uptake of THC, the exclusive application of (these two) topically applied products did not produce cannabinoid findings in blood or urine.