An approach to the evaluation of the potency of cannabis resin in Madrid: A health hazard?

The present study investigates the concentration of Delta (9)-tetrahidrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) in 60 samples of cannabis resin acquired on the streets of Madrid region and its potential danger to consumers' health. Additionally, we study the possible correlation between the potency of samples and their organoleptic characteristics. The analysis of cannabinoids was carried out using a high performance liquid chromatography (RP-HPLC-UV). To classify samples, a strength scale based on THC content was established. THC content in 76.7% of the samples was higher than 15%. This potency allows these samples to be classified as Schedule I or drugs with "unacceptable risk" for human health. THC content in 36.7% of the samples was 28.8% on average, which means very high potency. The mean CBD content was 5%, while the correlation between the CBD/THC ratio and potency was negative. The mean content of CBN was 1.74% and the CBN/THC ratio also showed a negative correlation in respect to potency. When investigating the possible correlation between sample potency and organoleptic characteristics, those samples which simultaneously presented sticky texture, high elasticity and light brown colour had very high potency, with an average THC content of 28.7%. Our study shows that the THC content of most of the cannabis that can be purchased in Madrid region is over 15% and poses a health hazard. Additionally, we demonstrate for the first time that only those samples with very high potency can be directly associated with certain organoleptic characteristics.