ToxSci Advance Access first published online on August 14, 2008
This version published online on August 21, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn163
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Buprenorphine alters desmethylflunitrazepam disposition and flunitrazepam toxicity in rats

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* INSERM U705, CNRS, UMR7157, Université Paris-Descartes, and Université Paris-Diderot, Paris F-75018, France
Laboratoire de Toxicologie de l'Institut National de Police Scientifique, Paris F-75012, France
Réanimation Médicale et Toxicologique, Hôpital Lariboisière, Paris F-75010, France
Department of Surgery, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC 7736, San Antonio, TX 78229, USA
¶ DCMR, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau, France
|| Laboratoire de Biomathématiques, Université Paris-Descartes, 75006 Paris, France
1 To whom correspondence should be addressed at Réanimation Médicale et Toxicologique, Hôpital Lariboisière, 2 Rue Ambroise Paré, 75010 Paris, France. Telephone number: (+33)-1-49-95-89-61, Fax number: (+33)-1-49-95-65-78. E-mail: bruno-megarbane{at}wanadoo.fr
Received June 5, 2008; revision received August 3, 2008; accepted August 4, 2008
| Abstract |
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High-dosage buprenorphine (BUP) consumed concomitantly with benzodiazepines including flunitrazepam (FZ) may cause life-threatening respiratory depression despite a BUP ceiling effect and benzodiazepines' limited effects on ventilation. However, the mechanism of BUP/FZ interaction remains unknown. We hypothesized that BUP may alter the disposition of FZ active metabolites in vivo, contributing to respiratory toxicity. Plasma FZ, desmethylflunitrazepam (DMFZ), and 7-aminoflunitrazepam (7-AFZ) concentrations were measured using gas chromatography-mass spectrometry. Intravenous BUP 30 mg.kg-1 pretreatment did not alter plasma FZ and 7-AFZ kinetics in Sprague-Dawley rats infused with 40 mg.kg-1 FZ over 30 min, while resulting in a three-fold increase in the area-under-the-curve of DMFZ concentrations compared with control (p<0.01). In contrast, BUP did not significantly modify plasma DMFZ concentrations after intravenous infusion of 7mg.kg-1 DMFZ, while resulting in a similar peak concentration to that generated from 40 mg.kg-1 FZ administration. Regarding the effects on ventilation, BUP (30 mg.kg-1) as well as its combination with FZ (0.3 mg.kg-1) significantly increased PaCO2 while only BUP/FZ combination decreased PaO2 (p<0.001). Interestingly, FZ (40 mg.kg-1) but not DMFZ (40 mg.kg-1) significantly increased PaCO2 (p<0.05), whereas DMFZ but not FZ decreased PaO2 (p<0.05). Thus, decrease in PaO2 appears related to BUP-mediated effects on DMFZ disposition while increases in PaCO2 relate to direct BUP/FZ additive or synergistic dynamic interactions. We conclude that combined high-dosage BUP and FZ is responsible for increased respiratory toxicity in which BUP-mediated alteration in DMFZ disposition may play a significant role.
Key Words: Buprenorphine; Desmethylflunitrazepam; Flunitrazepam; Interaction; Metabolism; Pharmacokinetics.
E-mail addresses: pirnaystephane{at}yahoo.com; bruno-megarbane{at}wanadoo.fr; xavier.decleves{at}univ-paris5.fr; patricia.risede{at}inserm.fr; borron{at}uthscsa.edu; stephane.bouchonnet{at}dcmr.polytechnique.fr; b.perrin{at}wanadoo.fr; marcel.debray{at}univ-paris5.fr; n.Milan{at}yahoo.fr; tania.m.duarte{at}gmail.com; prefpol-labotoxico.directeur{at}wanadoo.fr; frederic.baud{at}lrb.aphp.fr