An in vitro approach to estimate putative inhibition of buprenorphine and norbuprenorphine glucuronidation.

An in vitro inhibition study was performed to investigate potential drug-drug interactions on glucuronidation of buprenorphine (BUP) and norbuprenorphine (NBUP), which represents the major elimination pathway of the drug using cDNA-expressed uridine 5'-diphosphate glucuronosyltransferases (UGTs) and human liver microsomes (HLMs). Following identification of major UGT enzymes for BUP and NBUP glucuronidation, substrates were incubated with drugs (amitriptyline, nortriptyline, lamotrigine, oxazepam, and temazepam), which are extensively cleared by glucuronidation as well as are often used during maintenance treatment. To evaluate the inhibitory potential, the half maximal inhibitor concentration (IC(50)), the inhibition constant (K (i)), and the inhibitor concentration (K (I)) that yield half the maximum rate of inactivation and the enzyme inactivation rate constant (k (inact)) were determined, if appropriate. Amitriptyline and temazepam are inhibitors of NBUP glucuronidation (UGT1A3, HLMs), whereas BUP glucuronidation was affected by amitriptyline (HLMs), oxazepam, and temazepam (UGT2B7). Additionally, BUP inhibits NBUP glucuronidation (UGT1A1, 1A3, HLMs) and vice versa (UGT1A3). A decrease in the metabolic clearance of NBUP may increase the risk of adverse effects such as respiratory depression. Further investigations are needed to evaluate whether inhibition of BUP and NBUP glucuronidation contributes to adverse events.

Buprenorphine and major metabolites in blood specimens collected for drug analysis in law enforcement purposes.

A liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of buprenorphine (BUP), norbuprenorphine (NBUP), buprenorphine-3-beta-D-glucuronide (BUPG) and norbuprenorphine-3-beta-D-glucuronide (NBUPG) in serum samples was developed and validated. Pre-treatment of BUP and NBUP was by liquid-liquid extraction, while glucuronides were favourably isolated by solid phase extraction. Separation in 2 separate runs (2 x 5 min) was achieved using isocratic elution. The method was applied to 20 authentic serum specimens collected for law enforcement purposes where BUP intake had been indicated. The parent drug was not detectable in half of the specimens at a lower limit of detection of 0.2 ng/mL, whereas NBUP could be determined from any sample but one. NBUPG is the major metabolite present, which could be identified along with BUPG in all samples under investigation. In authentic specimens it could be advisable to monitor BUP metabolites along with the parent drug.

[Has the transdermal patch gone up in smoke? A fatal fentanyl intoxication]. / Hatte sich das Pflaster in Rauch aufgelöst?-- Eine tödliche Fentanylintoxikation.

Recently, there has been an increase in fentanyl-related overdoses following administration of transdermal patches by the buccal, oral or intravenous route or via inhalation. A fatal intoxication is reported with clear evidence from toxicological analysis. However, the administration route and the fate of the patch remained elusive at the end of the investigations. Alcohol was present in the blood in small quantity (0.024%), whereas no other drug could be detected by basic strategies. Autopsy and microscopic examination failed to find sufficient evidence for a diagnosis. Fentanyl and norfentanyl were determined from body fluids and tissues by LC/MS/MS following liquid/liquid extraction. Both analytes were detectable in all specimens under investigation except muscle tissue where norfentanyl was absent. While the fentanyl concentration in the blood was considered potentially life-threatening on the basis of data obtained from living persons and fentanyl-related deaths, it was difficult to assess the other values because no comparative data were available. The history and circumstances of the case together with the toxicological findings suggest an intravenous or inhalative application of the patch. The latter assumption is supported by the fact that the body was found holding a cigarillo butt in his right hand. The case underlines the necessity to study fentanyl-related deaths more closely to allow a better interpretation of potential intoxications.