Drug General Information (ID: DDI0THZXO9)
  Drug Name Omeprazole Drug Info Itraconazole Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Antiulcer Agents Antifungal Agents
  Structure

 Mechanism of Omeprazole-Itraconazole Interaction (Severity Level: Moderate)
     Altered gastric pH Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Omeprazole Itraconazole
      Mechanism 1 Gastric alkalinizer Gastric pH sensitive
      Key Mechanism Factor 1
Factor Name Gastric pH
Factor Description The normal pH range of gastric acid is between 1.5 and 3.5 and is highly acidic, consisting mainly of hydrochloric acid. Changes in the pH of the stomach can alter the absorption of drugs.
      Mechanism Description
  • Decreased absorption of Itraconazole due to altered gastric pH caused by Omeprazole 
     CYP450 enzyme inhibition Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Omeprazole Itraconazole
      Mechanism 2 CYP450 3A4 substrate CYP450 3A4 inhibitor
      Key Mechanism Factor 2
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 Omeprazole caused by Itraconazole mediated inhibition of CYP450 enzyme

Recommended Action
      Management In general, the concomitant use of these drugs is not recommended. If coadministration is necessary, an acidic pH may be produced with two capsules of glutamic acid hydrochloride administered 15 minutes before the azole dose. Administration with an acidic beverage such as Coca-Cola(R) may also help. Additionally, an increase of the antifungal dosage may be required. However, clinicians should still consider the possibility of a reduced or subtherapeutic antifungal effect. It may be appropriate to switch to itraconazole oral solution or an agent like fluconazole whose absorption is not affected by stomach pH.

References
1 Bottiger Y, Tybring G, Gotharson E, Bertilsson L "Inhibition of the sulfoxidation of omeprazole by ketoconazole in poor and extensive metabolizers of S-mephenytoin." Clin Pharmacol Ther 62 (1997): 384-91. [PMID: 9357389]
2 Carlson JA, Mann HJ, Canafax DM "Effect of pH on disintegration and dissolution of ketoconazole tablets." Am J Hosp Pharm 40 (1983): 1334-6. [PMID: 6310994]
3 Chin TWF, Loeb M, Fong IW "Effects of an acidic beverage (coca-cola) on absorption of ketoconazole." Antimicrob Agents Chemother 39 (1995): 1671-5. [PMID: 7486898]
4 Jaruratanasirikul S, Sriwiriyajan S "Effect of omeprazole on the pharmacokinetics of itraconazole." Eur J Clin Pharmacol 54 (1998): 159-61. [PMID: 9626921]
5 Katz HI "Drug interactions of the newer oral antifungal agents." Br J Dermatol 141 (1999): 26-32. [PMID: 10730911]
6 Piscitelli SC, Goss TF, Wilton JH, D'Andrea DT, Goldstein H, Schentag JJ "Effects of ranitidine and sucralfate on ketoconazole bioavailability." Antimicrob Agents Chemother 35 (1991): 1765-71. [PMID: 1952845]
7 Product Information. Aciphex (rabeprazole) Janssen Pharmaceuticals, Titusville, NJ.
8 Product Information. Nexium (esomeprazole) Astra-Zeneca Pharmaceuticals, Wilmington, DE.
9 Product Information. Prevacid (lansoprazole). TAP Pharmaceuticals Inc, Deerfield, IL.
10 Product Information. Prilosec (omeprazole). Merck & Co, Inc, West Point, PA.
11 Product Information. Protonix (pantoprazole) Wyeth-Ayerst Laboratories, Philadelphia, PA.
12 Van der Meer JW, Keuning JJ "The influence of gastric acidity on the bio-availability of ketoconazole." J Antimicrob Chemother 6 (1980): 552-4. [PMID: 6253434]