Analytical quantification, intoxication case series, and pharmacological mechanism of action for N‐ethylnorpentylone (N‐ethylpentylone or ephylone)

: Synthetic cathinones continue to proliferate in clandestine drug markets worldwide. N-ethylnorpentylone (also known as N-ethylpentylone or ephylone) is a popular emergent cathinone, yet little information is available about its toxicology and pharmacology. Here we characterize the analytical quantification, clinical presentation, and pharmacological mechanism of action for N-ethylnorpentylone. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to quantify N-ethylnorpentylone in blood obtained from human cases. Clinical features exhibited by the intoxicated individuals are described. The activity of N-ethylnorpentylone at plasma membrane transporters for dopamine (DAT), norepinephrine (NET) and 5-HT (SERT) was assessed using in vitro assays measuring uptake inhibition and evoked release of [3 H] neurotransmitters in rat brain synaptosomes. Our LC-MS/MS method assayed N-ethylnorpentylone concentrations with limits of detection and quantification of 1 and 5 ng/mL, respectively. Quantitation was linear from 5 to 500 ng/mL, and the method displayed specificity and reproducibility. Circulating concentrations of N-ethylnorpentylone ranged from 7 to 170 ng/mL in clinical cases, and the associated symptoms included palpitations, tachycardia, agitation, hallucinations, coma and death. N-Ethylnorpentylone was a potent inhibitor at DAT (IC50  = 37 nM), NET (IC50  = 105 nM) and SERT (IC50  = 383 nM) but displayed no transporter releasing activity. We present a validated method for quantifying N-ethylnorpentylone in human case work. The drug is a psychomotor stimulant capable of inducing serious cardiovascular and neurological side-effects which can be fatal. In vitro findings indicate that N-ethylnorpentylone exerts its effects by potent blockade of DAT and NET, thereby elevating extracellular levels of dopamine and norepinephrine in the brain and periphery.