Azole antifungal inhibition of buprenorphine methadone and oxycodone in vitro metabolism

• NCJ Number: 255734
• Journal: Journal of Analytical Toxicology Volume: 39 Issue: 5 Dated: 2015 Pages: 374-386
• Author(s): David E. Moody; Fenyun Liu; Wenfang B. Fang
• Date Published: 2015
• Length: 13 pages
• Grant Number(s): 2011-DN-BX-K532
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)
• Award: Prediction of drug interactions with methadone, buprenorphine and oxycodone from in vitro inhibition of metabolism

Annotation

This article examined the inhibitory effect of 12 azoles in an attempt to identify drug interactions that increase blood opioid concentrations which can lead to unintended deaths.

Abstract

Opioid-related mortality rates have escalated. Drug interactions may increase blood concentrations of the opioid. The authors therefore used human liver microsomes (HLMs) and cDNA-expressed human cytochrome P450s (rCYPs) to study in vitro inhibition of buprenorphine metabolism to norbuprenorphine (CYP3A4 and 2C8), oxycodone metabolism to noroxycodone (CYP3A4 and 2C18) and oxymorphone (CYP2D6), and methadone metabolism to R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP; CYP3A4 and 2B6). In this study, the authors have examined the inhibitory effect of 12 (mostly antifungal) azoles. These compounds have a wide range of solubility; to keep organic solvent ≤1%, there was an equally wide range of highest concentration tested (e.g., itraconazole 5 µM to fluconazole 1000 µM). Inhibitors were first incubated with HLMs at three concentrations with or without preincubation of inhibitor with reducing equivalents to also screen for time-dependent inhibition (TDI). Posaconazole displayed evidence of TDI; metronidazole and albendazole had no significant effect. Azoles were next screened at the highest achievable concentration for non-CYP3A4 pathways. IC₅₀ values (µM) were determined for most CYP3A4 pathways (ranges) and other pathways as dictated by screen results: clotrimazole (0.30 – 0.35; others >30 µM); econazole (2.2 – 4.9; 2B6 R-EDDP – 9.5, S-EDDP – 6.8; 2C8 – 6.0; 2C18 – 1.0; 2D6 – 1.2); fluconazole (7.7 – 66; 2B6 – 313, 361; 2C8 – 1240; 2C18 – 17; 2D6 – 1000); itraconazole (2.5 to >5; others >5); ketoconazole (0.032 – 0.094; 2B6 – 12, 31; 2C8 – 78; 2C18 – 0.98; 2D6 – 182); miconazole (2.3 – 7.6; 2B6 – 2.8, 2.8; 2C8 – 5.3; 2C18 – 3.1; 2D6 – 5.9); posaconazole (3.4 – 20; 2C18 – 3.8; others >30); terconazole (0.48 to >10; 2C18 – 8.1; others >10) and voriconazole (0.40 – 15; 2B6 – 2.4, 2.5; 2C8 – 170; 2C18 – 13; 2D6 >300). Modeling based on estimated K_i values and plasma concentrations from the literature suggest that the orally administered azoles, particularly ketoconazole and voriconazole, have the greatest potential for inhibiting CYP3A4 pathways, as does voriconazole for the CYP2B6 pathways. Azoles used for mucosal and topical applications did not exceed the modeling threshold. (Published Abstract Provided)