Toxicological evaluation, postmortem case descriptions, and pharmacological activity of <i>N</i>,<i>N</i>-dimethylpentylone and related analogs

Identification of N,N-dimethylpentylone (DMP) in counterfeit "Ecstasy" and "Molly" tablets poses risk to public health due to its adverse effects. Little information is available regarding the pharmacological activity or relevant blood or tissue concentrations of DMP, and even less is known about other structurally related beta-keto methylenedioxyamphetamine analogs on recreational drug markets, such as N-propyl butylone. Here, a novel toxicological assay utilizing liquid chromatography-tandem quadrupole mass spectrometry was developed and validated for the quantitation of DMP and five related synthetic cathinones [eutylone, pentylone, N-ethyl pentylone (NEP), N-propyl butylone, and N-cyclohexyl butylone], with chromatographic resolution from isomeric variants and quantitation performed by standard addition. A forensic series of 125 cases is presented for DMP and related analogs, along with pharmacological activity assessments using monoamine transporter and mouse behavioral assays. The blood concentration range for DMP in postmortem forensic cases was 3.3-4600 ng/mL (mean: 320 ± 570 ng/mL, median: 150 ng/mL), whereas pentylone, the primary N-desmethyl metabolite of DMP, was identified in 98% of cases with a concentration range 1.3-710 ng/mL (mean ± SD: 105 ± 120 ng/mL, median: 71 ng/mL). N-Propyl butylone, a newly identified synthetic cathinone, was quantitated in seven cases (mean ± SD: 82 ± 75 ng/mL, median: 50 ng/mL, range: 1.7-200 ng/mL). DMP displayed potent uptake inhibition at the dopamine transporter [half maximal inhibitory concentration (IC50) of 49 nM], with 100-fold weaker potency at the serotonin transporter (IC50 = 4990 nM). DMP was a locomotor stimulant in mice [medium effective dose (ED50) of 3.5 mg/kg] exhibiting potency relatively similar to eutylone, NEP, and pentylone. Our results show that DMP is a psychomotor stimulant associated with adverse clinical outcomes leading to death. Forensic laboratories must continue to update testing methods to capture emerging drugs, with specific emphasis on resolution and identification of isomeric species. Following the scheduling of DMP in early 2024, there could be an anticipated market shift toward a new unregulated synthetic stimulant to replace DMP.