Urine Analysis of Buprenorphine/Norbuprenorphine/Naloxone in Drugs and Driving Cases

It was Robinson who elucidated the active structure of morphine in 1925. Buprenorphine (2S)-2-[(5R,6R,7R,14S)-9αCyclopropylmethyl-4,5-epoxy-6,14-ethano-3-hydroxy-6methoxymorphinan-7-yl]-3,3-dimethylbutan-2-ol) which is a semi-synthetic opioid. It possesses partial agonist properties acting at μ-opioid receptor site, it also possesses antagonist characteristics acting mainly on the κ-opioid receptor site [1]. Its structure is derived from thebaine, and it has a structural similarity with morphine ((5α,6α)-7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diol), but has been reported to be up to 50 times more potent, with a higher affinity for μ-opioid receptors compared with other opioids, including heroin (diacetyl morphine)[2]. Historically, buprenorphine was first synthesized 1966 by John Lewis working at Reckitt and Colman (later Reckitts). Lewis had previously been a doctoral student of Sir Robert Robinson, who had elucidated the active structure of morphine in 1925 [3]. Buprenorphine (BUP) is metabolized in human beings through to the active metabolite norbuprenorphine (NBUP) via the process of N-dealkylation, performed primarily by cytochrome P450 (CYP 450) 3A4 and CYP 2D6 groups of enzymes [4]. Minor metabolites of BUP and NBUP i.e hydroxybuprenorphine and hydroxynorbuprenorphine have also been reported [5], these are believed to occur after oxidation of the tertiary butyl group on both BUP and NBUP but do not make a significant contribution to the urinary profile. Peak plasma concentration times of BUP have reported to range from 0.66 hours to 3.5 hours, its halflife (t1/2) has been reported to be as long as 44 hours [6]. NBUP the primary metabolite of buprenorphine is by nature is a weak opiate agonist and has been reported as having a potency of one quarter of buprenorphine. It has also been reported that it possesses greater respiratory depressant effects than the parent and this phenomenon may controlled not by brain based opioid receptors but those located in the lung [7]. The half-life for NBUP JOURNAL OF APPLIED BIOANALYSIS, July 2015, p. 80-88. http://dx.doi.org/10.17145/jab.15.014 (ISSN 2405-710X) Vol. 1, No. 3