Pharmacodynamic Effects, Pharmacokinetics, and Metabolism of the Synthetic Cannabinoid AM-2201 in Male Rats.

Novel synthetic cannabinoids are appearing in recreational drug markets worldwide. Pharmacological characterization of these new drugs is needed to inform clinicians, toxicologists, and policy makers who monitor public health. [1-(5-Fluoropentyl)-1H-indol-3-yl](1-naphthyl)methanone (AM-2201) is an abused synthetic cannabinoid that was initially created as a research tool for investigating the endocannabinoid system. Here we measured the pharmacodynamic effects of AM-2201 in rats, and simultaneously determined plasma pharmacokinetics for the parent drug and its metabolites. Male Sprague-Dawley rats were fitted with surgically implanted temperature transponders and indwelling jugular catheters under pentobarbital anesthesia. One week later, rats received subcutaneous injection of AM-2201 (0.1, 0.3, and 1.0 mg/kg) or its vehicle, and serial blood specimens were withdrawn via catheters. Core temperatures and catalepsy were measured just prior to each blood withdrawal, and plasma was assayed for drug and metabolites using liquid chromatography-tandem mass spectrometry. We found that AM-2201 produced dose-related hypothermia and catalepsy that peaked at 2 hours and lasted up to 8 hours. AM-2201 plasma concentrations rose linearly with increasing dose and ranged from 0.14 to 67.9 µg/l. Concentrations of three metabolites, AM-2201 N-(4-hydroxypentyl) (≤0.17 µg/l), naphthalen-1-yl-(1-pentylindol-3-yl)methanone (JWH-018) N-(5-hydroxypentyl) (≤1.14 µg/l), and JWH-018 N-pentanoic acid (≤0.88 µg/l) were detectable but much lower. Peak AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid concentrations occurred at 1.3, 2.4, and 6.5 hours, respectively. Concentrations of AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid were negatively correlated with body temperature, but, given the low concentrations of metabolites detected, AM-2201 is likely the major contributor to pharmacodynamic effects under our experimental conditions.

Quantification of [1-(5-fluoropentyl)-1H-indol-3-yl](naphthalene-1-yl)methanone (AM-2201) and 13 metabolites in human and rat plasma by liquid chromatography-tandem mass spectrometry.

AM-2201 is a popular synthetic cannabinoid first synthesized in 2000. AM-2201 pharmacokinetic and pharmacodynamic data are scarce, requiring further investigation. We developed a sensitive method for quantifying AM-2201 and 13 metabolites in plasma to provide a tool to further metabolic, pharmacokinetic and pharmacodynamic studies. Analysis was performed by liquid chromatography-tandem mass spectrometry. Chromatographic separation was performed by gradient elution on a biphenyl column with 0.1% formic acid in water/0.1% formic acid in acetonitrile:methanol 50:50 (v/v) mobile phase. Sample preparation (75µL) consisted of an enzymatic hydrolysis and a supported liquid extraction. The method was validated with human plasma with a 0.025 or 0.050-50µg/L working range, and cross-validated for rat plasma. Analytical recovery was 88.8-110.1% of target concentration, and intra- (n=30) and inter-day (n=30) imprecision<11.9% coefficient of variation. Method recoveries and matrix effects ranged from 58.4-84.4% and -62.1 to -15.6%, respectively. AM-2201 and metabolites were stable (±20%) at room temperature for 24h, at 4°C for 72h, and after three freeze-thaw cycles, and for 72h in the autosampler after extraction. The method was developed for pharmacodynamic and pharmacokinetic studies with controlled administration in rats but is applicable for pre-clinical and clinical research and forensic investigations. Rat plasma specimen analysis following subcutaneous AM-2201 administration demonstrated the suitability of the method. AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid concentrations were 4.8±1.0, 0.15±0.03, and 0.34±0.07µg/L, respectively, 8h after AM-2201 administration at 0.3mg/kg (n=5).