Details of Drug Interaction | MecDDI

Drug General Information (ID: DDIT7YNWZC)
Drug Name			Methadone		Drug Info		Conivaptan		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Analgesics				Vasopressin Antagonists
Structure

Mechanism of Methadone-Conivaptan Interaction (Severity Level: Moderate)
CYP450 enzyme inhibition Click to Show/Hide Mechanism Graph

Drug Name		Methadone				Conivaptan
Mechanism		CYP450 3A4 substrate				CYP450 3A4 inhibitor
Key Mechanism Factor 1
		Factor Name		Cytochrome P450 3A4				× Structure Sequence MALIPDLAMETWLLLAVSLVLLYLYGTHSHGLFKKLGIPGPTPLPFLGNILSYHKGFCMFDMECHKKYGKVWGFYDGQQPVLAITDPDMIKTVLVKECYSVFTNRRPFGPVGFMKSAISIAEDEEWKRLRSLLSPTFTSGKLKEMVPIIAQYGDVLVRNLRREAETGKPVTLKDVFGAYSMDVITSTSFGVNIDSLNNPQDPFVENTKKLLRFDFLDPFFLSITVFPFLIPILEVLNICVFPREVTNFLRKSVKRMKESRLEDTQKHRVDFLQLMIDSQNSKETESHKALSDLELVAQSIIFIFAGYETTSSVLSFIMYELATHPDVQQKLQEEIDAVLPNKAPPTYDTVLQMEYLDMVVNETLRLFPIAMRLERVCKKDVEINGMFIPKGVVVMIPSYALHRDPKYWTEPEKFLPERFSKKNKDNIDPYIYTPFGSGPRNCIGMRFALMNMKLALIRVLQNFSFKPCKETQIPLKLSLGGLLQPEKPVVLKVESRDGTVSGA
		Gene Name		CYP3A4
		Uniprot ID		CP3A4_HUMAN
		KEGG Pathway		hsa:1576
		Protein Family		Cytochrome P450 family
		Protein Function		A cytochrome P450 monooxygenase involved in the metabolism of sterols, steroid hormones, retinoids and fatty acids (PubMed:10681376, PubMed:11093772, PubMed:11555828, PubMed:14559847, PubMed:12865317, PubMed:15373842, PubMed:15764715, PubMed:20702771, PubMed:19965576, PubMed:21490593, PubMed:21576599). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (NADPH--hemoprotein reductase). Catalyzes the hydroxylation of carbon-hydrogen bonds (PubMed:2732228, PubMed:14559847, PubMed:12865317, PubMed:15373842, PubMed:15764715, PubMed:21576599, PubMed:21490593). Exhibits high catalytic activity for the formation of hydroxyestrogens from estrone (E1) and 17beta-estradiol (E2), namely 2-hydroxy E1 and E2, as well as D-ring hydroxylated E1 and E2 at the C-16 position (PubMed:11555828, PubMed:14559847, PubMed:12865317). Plays a role in the metabolism of androgens, particularly in oxidative deactivation of testosterone (PubMed:2732228, PubMed:15373842, PubMed:15764715, PubMed:22773874). Metabolizes testosterone to less biologically active 2beta- and 6beta-hydroxytestosterones (PubMed:2732228, PubMed:15373842, PubMed:15764715). Contributes to the formation of hydroxycholesterols (oxysterols), particularly A-ring hydroxylated cholesterol at the C-4beta position, and side chain hydroxylated cholesterol at the C-25 position, likely contributing to cholesterol degradation and bile acid biosynthesis (PubMed:21576599). Catalyzes bisallylic hydroxylation of polyunsaturated fatty acids (PUFA) (PubMed:9435160). Catalyzes the epoxidation of double bonds of PUFA with a preference for the last double bond (PubMed:19965576). Metabolizes endocannabinoid arachidonoylethanolamide (anandamide) to 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid ethanolamides (EpETrE-EAs), potentially modulating endocannabinoid system signaling (PubMed:20702771). Plays a role in the metabolism of retinoids. Displays high catalytic activity for oxidation of all-trans-retinol to all-trans-retinal, a rate-limiting step for the biosynthesis of all-trans-retinoic acid (atRA) (PubMed:10681376). Further metabolizes atRA toward 4-hydroxyretinoate and may play a role in hepatic atRA clearance (PubMed:11093772). Responsible for oxidative metabolism of xenobiotics. Acts as a 2-exo-monooxygenase for plant lipid 1,8-cineole (eucalyptol) (PubMed:11159812). Metabolizes the majority of the administered drugs. Catalyzes sulfoxidation of the anthelmintics albendazole and fenbendazole (PubMed:10759686). Hydroxylates antimalarial drug quinine (PubMed:8968357). Acts as a 1,4-cineole 2-exo-monooxygenase (PubMed:11695850). Also involved in vitamin D catabolism and calcium homeostasis. Catalyzes the inactivation of the active hormone calcitriol (1-alpha,25-dihydroxyvitamin D(3)) (PubMed:29461981). Click to Show/Hide
Mechanism Description		Decreased metabolism of Methadone caused by Conivaptan mediated inhibition of CYP450 enzyme

Recommended Action
Management		Caution is advised if methadone is prescribed in combination with CYP450 3A4 inhibitors. Pharmacologic response to methadone should be closely monitored and the dosage adjusted accordingly, particularly following initiation or discontinuation of the CYP450 3A4 inhibitor in patients who are stabilized on their methadone regimen. Patients should be advised to report excessive drowsiness, nausea, or asthenia to their physician, and to seek immediate medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope. ECG monitoring should be considered for patients on methadone with heart or liver disease conduction abnormalities electrolyte disturbances (i.e., hypokalemia, hypomagnesemia) concomitant use of drugs that may cause QT prolongation or electrolyte loss concomitant use of CYP450 3A4 inhibitors or use of methadone at dosages greater than 200 mg daily.

References
1	Bell J, Seres V, Bowron P, Lewis J, Batey R "The use of serum methadone levels in patients receiving methadone maintenance." Clin Pharmacol Ther 43 (1988): 623-9. [PMID: 3378383]
2	Ehret GB, Desmeules JA, Broers B "Methadone-associated long QT syndrome: improving pharmacotherapy for dependence on illegal opioids and lessons learned for pharmacology." Expert Opin Drug Saf 6 (2007): 289-303. [PMID: 17480178]
3	Foster DJ, Somogyi AA, Bochner F "Methadone N-demethylation in human liver microsomes: lack of stereoselectivity and involvement of CYP3A4." Br J Clin Pharmacol 47 (1999): 403-12. [PMID: 10233205]
4	Iribarne C, Berthou F, Baird S, Dreano Y, Picart D, Bail JP, Beaune P, Menez JF "Involvement of cytochrome P450 3A4 enzyme in the N-demethylation of methadone in human liver microsomes." Chem Res Toxicol 9 (1996): 365-73. [PMID: 8839037]
5	Krantz MJ, Lewkowiez L, Hays H, et al "Torsade de pointes associated with very-high-dose methadone." Ann Intern Med 137 (2002): 501-4. [PMID: 12230351]
6	Moody DE, Alburges ME, Parker RJ, Collings JM, Strong JM "The involvement of cytochrome P450 3A4 in the N-demethylation of L-alpha-acetylmethadol (LAAM), norLAAM, and methadone." Drug Metab Dispos 25 (1997): 1347-53. [PMID: 9394023]
7	Product Information. Stribild (cobicistat/elvitegravir/emtricitabine/tenofov). Gilead Sciences, Foster City, CA.
8	Oda Y, Kharasch ED "Metabolism of methadone and levo-alpha-acetylmethadol (LAAM) by human intestinal cytochrome P450 3A4 (CYP3A4): potential contribution of intestinal metabolism to presystemic clearance and bioactivation." J Pharmacol Exp Ther 298 (2001): 1021-32. [PMID: 11504799]