Drug General Information (ID: DDIPDCRA8M)
  Drug Name Toremifene Drug Info Anisindione Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Antineoplastics Anticoagulants
  Structure

 Mechanism of Toremifene-Anisindione Interaction (Severity Level: Moderate)
     CYP450 enzyme inhibition Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Toremifene Anisindione
      Mechanism CYP450 2C9 inhibitor CYP450 2C9 substrate
      Key Mechanism Factor 1
Factor Name Cytochrome P450 2C9
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Structure Sequence
MDSLVVLVLCLSCLLLLSLWRQSSGRGKLPPGPTPLPVIGNILQIGIKDISKSLTNLSKVYGPVFTLYFGLKPIVVLHGYEAVKEALIDLGEEFSGRGIFPLAERANRGFGIVFSNGKKWKEIRRFSLMTLRNFGMGKRSIEDRVQEEARCLVEELRKTKASPCDPTFILGCAPCNVICSIIFHKRFDYKDQQFLNLMEKLNENIKILSSPWIQICNNFSPIIDYFPGTHNKLLKNVAFMKSYILEKVKEHQESMDMNNPQDFIDCFLMKMEKEKHNQPSEFTIESLENTAVDLFGAGTETTSTTLRYALLLLLKHPEVTAKVQEEIERVIGRNRSPCMQDRSHMPYTDAVVHEVQRYIDLLPTSLPHAVTCDIKFRNYLIPKGTTILISLTSVLHDNKEFPNPEMFDPHHFLDEGGNFKKSKYFMPFSAGKRICVGEALAGMELFLFLTSILQNFNLKSLVDPKNLDTTPVVNGFASVPPFYQLCFIPV
Gene Name CYP2C9
Uniprot ID CP2C9_HUMAN
KEGG Pathway hsa:1559
Protein Family Cytochrome P450 family
Protein Function
A cytochrome P450 monooxygenase involved in the metabolism of various endogenous substrates, including fatty acids and steroids (PubMed:7574697, PubMed:9866708, PubMed:9435160, PubMed:12865317, PubMed:15766564, PubMed:19965576, 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) (PubMed:7574697, PubMed:9866708, PubMed:9435160, PubMed:12865317, PubMed:15766564, PubMed:19965576, PubMed:21576599). Catalyzes the epoxidation of double bonds of polyunsaturated fatty acids (PUFA) (PubMed:7574697, PubMed:15766564, PubMed:19965576, PubMed:9866708). Catalyzes the hydroxylation of carbon-hydrogen bonds. Metabolizes cholesterol toward 25-hydroxycholesterol, a physiological regulator of cellular cholesterol homeostasis (PubMed:21576599). Exhibits low catalytic activity for the formation of catechol estrogens from 17beta-estradiol (E2) and estrone (E1), namely 2-hydroxy E1 and E2 (PubMed:12865317). Catalyzes bisallylic hydroxylation and hydroxylation with double-bond migration of polyunsaturated fatty acids (PUFA) (PubMed:9866708, PubMed:9435160). Also metabolizes plant monoterpenes such as limonene. Oxygenates (R)- and (S)-limonene to produce carveol and perillyl alcohol (PubMed:11950794). Contributes to the wide pharmacokinetics variability of the metabolism of drugs such as S-warfarin, diclofenac, phenytoin, tolbutamide and losartan (PubMed:25994031).
    Click to Show/Hide
      Mechanism Description
  • Decreased metabolism of Anisindione caused by Toremifene mediated inhibition of CYP450 enzyme

Recommended Action
      Management Caution is advised if warfarin and other similar anticoagulants are used in combination with toremifene. The INR should be checked frequently and anticoagulant dosage adjusted accordingly, particularly following initiation or discontinuation of toremifene in patients who are stabilized on their anticoagulant regimen. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools.

References
1 Cerner Multum, Inc. "Australian Product Information.".
2 Cerner Multum, Inc. "UK Summary of Product Characteristics.".
3 Lodwick R, McConkey B, Brown AM, Beeley L "Life threatening interaction between tamoxifen and warfarin." Br Med J 295 (1987): 1141. [PMID: 3120919]
4 Product Information. Fareston (toremifene). Schering Laboratories, Kenilworth, NJ.
5 Product Information. Nolvadex (tamoxifen). Zeneca Pharmaceuticals, Wilmington, DE.
6 Ritchie LD, Grant SM "Tamoxifen-warfarin interaction: the Aberdeen hospitals drug file." BMJ 298 (1989): 1253. [PMID: 2502242]
7 Tenni P, Lalich DL, Byrne MJ "Life threatening interaction between tamoxifen and warfarin." BMJ 298 (1989): 93. [PMID: 2493305]