In vitro metabolism of the opioid tilidine and interaction of tilidine and nortilidine with CYP3A4, CYP2C19, and CYP2D6.
Tilidine is one of the most widely used narcotics in Germany and Belgium. The compound's active metabolite nortilidine easily penetrates the blood-brain barrier and activates the mu-opioid receptor. Thus far, the enzymes involved in tilidine metabolism are unknown. Therefore, the aim of our study was to identify the cytochrome P450 isozymes (CYPs) involved in N-demethylation of tilidine in vitro. We used human liver microsomes as well as recombinant CYPs to investigate the demethylation of tilidine to nortilidine and quantified nortilidine by liquid chromatography-tandem mass spectrometry. Inhibition of CYPs was quantified with commercial kits. Moreover, inhibition of ABCB1 and ABCG2 was investigated. Our results demonstrated that N-demethylation of tilidine to nortilidine followed a Michaelis-Menten kinetic with a K(m) value of 36 +/- 13 microM and a v(max) value of 85 +/- 18 nmol/mg/h. This metabolic step was inhibited by CYP3A4 and CYP2C19 inhibitors. Investigations with recombinant CYP3A4 and CYP2C19 confirmed that the demethylation of tilidine occurs via these two CYPs. Inhibition assays demonstrated that tilidine and nortilidine can also inhibit CYP3A4, CYP2C19, CYP2D6, ABCB1, but not ABCG2, whereas inhibition of CYP2D6 and possibly also of CYP3A4 might be clinically relevant. By calculating the metabolic clearance based on the in vitro and published in vivo data, CYP3A4 and CYP2C19 were identified as the main elimination routes of tilidine. In vivo, drug-drug interactions of tilidine with CYP3A4 or CYP2C19 inhibitors are to be anticipated, whereas substrates of CYP2C19, ABCB1, or ABCG2 will presumably not be influenced by tilidine or nortilidine.
Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Heidelberg, Germany. johanna.weiss@med.uni-heidelberg.de
Johanna
J
Weiss
Evelyn
E
Sawa
Klaus-Dieter
KD
Riedel
Walter Emil
WE
Haefeli
Gerd
G
Mikus
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors; D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors; D000701:Analgesics, Opioid / Q000378:metabolism* / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D065731:Cytochrome P-450 CYP2C19; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D065692:Cytochrome P-450 CYP3A Inhibitors; D004347:Drug Interactions; D004791:Enzyme Inhibitors; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008862:Microsomes, Liver / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D011994:Recombinant Proteins / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D013993:Tilidine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D000701:Analgesics, Opioid; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D065692:Cytochrome P-450 CYP3A Inhibitors; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; C073119:TAP1 protein, human; C062490:nortilidine; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D019389:Cytochrome P-450 CYP2D6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D013993:Tilidine