Norfentanyl [HRP]

The human ether-a-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium channel (I-Kr). Drug-mediated or medical condition-mediated disruption of hERG function is the primary cause of acquired long-QT syndrome, which predisposes affected individuals to ventricular arrhythmias and sudden death. Fentanyl abuse poses a serious health concern, with abuse and death rates rising over recent years. As fentanyl has a propensity to cause sudden death, we investigated its effects on the hERG channel. The effects of norfentanyl, the main metabolite, and naloxone, an antidote used in fentanyl overdose, were also examined. Currents of hERG channels stably expressed in HEK293 cells were recorded using the whole-cell voltage-clamp method. When hERG tail currents were analyzed upon -50 mV repolarization after a 50 mV depolarization, fentanyl and naloxone blocked hERG current (I-hERG) with IC50 values of 0.9 and 74.3 mu M, respectively, whereas norfentanyl did not block. However, fentanyl-mediated block of I-hERG was voltage dependent. When a voltage protocol that mimics a human ventricular action potential (AP) was used, fentanyl blocked I(hERG )with an IC50 of 0.3 mu M. Furthermore, fentanyl (0.5 mu M) prolonged AP duration and blocked I-Kr in ventricular myocytes isolated from neonatal rats. The concentrations of fentanyl used in this study were higher than seen with clinical use but overlap with postmortem overdose concentrations. Although mechanisms of fentanyl-related sudden death need further investigation, blockade of hERG channels may contribute to the death of individuals with high-concentration overdose or compromised cardiac repolarization.

The abuse of fentanyl and its analogues, which are potent, short-acting, synthetic narcotic analgesics, has become a major issue. Many cases containing fentanyl-analogue and novel synthetic opioids have also been reported. Hence, we report the determination of fentanyl, fentanyl-analogue and novel synthetic opioids in whole blood by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method is characterized by the use of a simple, fast and inexpensive liquid-liquid extraction (LLE) for sample preparation, a rapid run time (8 min) and a low required volume of whole blood (100 mu l). The limits of detection (LODs) ranged from 0.005 to 0.03 ng/ml, and the lower limits of quantitation (LLOQs) ranged from 0.05 to 0.2 ng/ml. The method was shown to be liner over a concentration range of 0.2-40 ng/ml for fentanyl, norfentanyl and norcarfentanil and 0.05-40 ng/ml for all other target analytes. Recoveries were within the range of 72.09%-103.22%, and the matrix effects were in the 67.95%-113.32% range. Moreover, the method was applied to the detection and quantification of fentanyl and its analogues in whole blood from real forensic cases. This methodology has great potential for use in the determination of fentanyl and its analogues in forensic cases.