Testing for AB-PINACA in human hair: Distribution in head hair versus pubic hair

Synthetic cannabinoid receptor agonists were first identified in herbal products in 2008 advertised as a legal replacement for cannabis. These herbal incense are usually called "spice" and among these, one product in particular has gained popularity: AB-PINACA (N-[(2S)-1-Amino-3-methyl-1-oxobutan-2-yl]-1-pentyl-1H-indazole-3-carboxamide). This drug has been discovered to have a stronger binding to human cannabinoid CB₁ and CB₂ receptors than ∆⁹ -THC.While some articles have been published regarding the presence of AB-PINACA in biological fluids such as blood and urine, none reports the presence of AB-PINACA in hair. We have developed and validated a method for detection of AB-PINACA in hair using a liquid chromatography-tandem mass spectrometry system and applied it to head and pubic hair obtained in a case of intoxication. The validation procedure demonstrated a limit of detection and a limit of quantification of 0.5 and 1 pg/mg, respectively and acceptable linearity, repeatability, and reproducibility. AB-PINACA tested positive in the blood (5.7 ng/mL) and less than 1 ng/mL was found in urine. The analysis of the hair specimens resulted in an unusual distribution of the drug between head and pubic hair. AB-PINACA was identified at a higher concentration in head hair (195 pg/mg) versus in pubic hair (5 pg/mg). The very low concentration of AB-PINACA in the urine after consumption, due to rapid metabolism, could explain this infrequent distribution, as pubic hair can be contaminated by urine. In any case, it cannot be excluded that the high concentration in head hair may be due to environmental contamination.