Submitted Successfully!
Thank you for your contribution! You can also upload a video entry related to this topic through the link below:
Check Note
Ver. Summary Created by Modification Content Size Created at Operation
1 + 436 word(s) 436 2020-12-15 07:49:48

Cytochrome P450 Family 2 Subfamily C Member 9

  • genes

1. Normal Function

The CYP2C9 gene provides instructions for making an enzyme that is found in a cell structure called the endoplasmic reticulum, which is involved in protein processing and transport. The CYP2C9 enzyme breaks down (metabolizes) compounds including steroid hormones and fatty acids. The CYP2C9 enzyme also plays a major role in breaking down the drug warfarin, which thins the blood and prevents blood clots from forming. This enzyme also assists in metabolizing other drugs such as ibuprofen, which reduces inflammation.

2. Health Conditions Related to Genetic Changes

2.1 Warfarin Sensitivity

Certain common CYP2C9 gene variations (polymorphisms) have been associated with warfarin sensitivity, a condition in which individuals require lower doses of the drug warfarin than are usually prescribed. Warfarin is an anticoagulant, which means that it thins the blood, preventing blood clots from forming.

The CYP2C9 gene polymorphisms associated with warfarin sensitivity change single protein building blocks (amino acids) in the CYP2C9 enzyme. The altered enzyme slows the breakdown (metabolism) of warfarin, allowing the drug to remain active in the body for a longer period of time. People with warfarin sensitivity take longer than usual to metabolize warfarin and may require lower doses of the drug than are usually prescribed.

The two most common CYP2C9 polymorphisms in people of European ancestry are known as CYP2C9*2 and CYP2C9*3. Both of these polymorphisms lead to a decrease in warfarin metabolism to such degrees that prescription doses are typically reduced by one-third and one-fifth, respectively. In individuals with African ancestry, the four most common CYP2C9 polymorphisms associated with warfarin sensitivity are known as CYP2C9*5, CYP2C9*6, CYP2C9*8, and CYP2C9*11. These polymorphisms lead to a decrease in warfarin metabolism that would necessitate a reduction in prescription doses by one-third to one-sixth. In other populations, the effects of these polymorphisms are less certain but are an active area of research.

In rare cases in which individuals have more than one CYP2C9 polymorphisms, the enzyme activity is severely decreased and metabolism of warfarin is very slow. If people with warfarin sensitivity take the average dose (or more) of warfarin, they are at risk of an overdose, which can cause abnormal bleeding in the brain, gastrointestinal tract, or other tissues, and may lead to serious health problems or death.

3. Other Names for This Gene


  • cytochrome P-450MP

  • cytochrome P450 2C9

  • cytochrome P450 MP-4

  • cytochrome P450 MP-8

  • cytochrome P450 PB-1

  • cytochrome P450, family 2, subfamily C, polypeptide 9

  • cytochrome P450, family 2, subfamily C, polypeptide 9 gene

  • P450 MP-4

  • S-mephenytoin 4-hydroxylase

  • S-mephenytoin 4-hydroxylase, human

  • warfarin-7-hydroxylase, human


  1. Ferder NS, Eby CS, Deych E, Harris JK, Ridker PM, Milligan PE, Goldhaber SZ,King CR, Giri T, McLeod HL, Glynn RJ, Gage BF. Ability of VKORC1 and CYP2C9 topredict therapeutic warfarin dose during the initial weeks of therapy. J ThrombHaemost. 2010 Jan;8(1):95-100. doi: 10.1111/j.1538-7836.2009.03677.x.
  2. Flockhart DA, O'Kane D, Williams MS, Watson MS, Flockhart DA, Gage B, GandolfiR, King R, Lyon E, Nussbaum R, O'Kane D, Schulman K, Veenstra D, Williams MS,Watson MS; ACMG Working Group on Pharmacogenetic Testing of CYP2C9, VKORC1Alleles for Warfarin Use. Pharmacogenetic testing of CYP2C9 and VKORC1 allelesfor warfarin. Genet Med. 2008 Feb;10(2):139-50. doi:10.1097/GIM.0b013e318163c35f.
  3. Moyer TP, O'Kane DJ, Baudhuin LM, Wiley CL, Fortini A, Fisher PK, Dupras DM,Chaudhry R, Thapa P, Zinsmeister AR, Heit JA. Warfarin sensitivity genotyping: a review of the literature and summary of patient experience. Mayo Clin Proc. 2009 Dec;84(12):1079-94. doi: 10.4065/mcp.2009.0278. Review.
  4. Perera MA, Cavallari LH, Limdi NA, Gamazon ER, Konkashbaev A, Daneshjou R,Pluzhnikov A, Crawford DC, Wang J, Liu N, Tatonetti N, Bourgeois S, Takahashi H, Bradford Y, Burkley BM, Desnick RJ, Halperin JL, Khalifa SI, Langaee TY, LubitzSA, Nutescu EA, Oetjens M, Shahin MH, Patel SR, Sagreiya H, Tector M, Weck KE,Rieder MJ, Scott SA, Wu AH, Burmester JK, Wadelius M, Deloukas P, Wagner MJ,Mushiroda T, Kubo M, Roden DM, Cox NJ, Altman RB, Klein TE, Nakamura Y, JohnsonJA. Genetic variants associated with warfarin dose in African-Americanindividuals: a genome-wide association study. Lancet. 2013 Aug31;382(9894):790-6. doi: 10.1016/S0140-6736(13)60681-9.
  5. van der Zee SA, Halperin JL. Anticoagulant therapy: warfarin sensitivitygenotyping closer to clinical practice. Nat Rev Cardiol. 2010 Oct;7(10):549-50.doi: 10.1038/nrcardio.2010.126.
Contributor :
View Times: 45
Entry Collection: MedlinePlus
Revision: 1 times (View History)
Update Time: 23 Dec 2020
Table of Contents


    Are you sure to Delete?

    Video Upload Options

    Do you have a full video?
    If you have any further questions, please contact Encyclopedia Editorial Office.
    Li, V. CYP2C9 Gene. Encyclopedia. Available online: (accessed on 25 September 2022).
    Li V. CYP2C9 Gene. Encyclopedia. Available at: Accessed September 25, 2022.
    Li, Vivi. "CYP2C9 Gene," Encyclopedia, (accessed September 25, 2022).
    Li, V. (2020, December 23). CYP2C9 Gene. In Encyclopedia.
    Li, Vivi. ''CYP2C9 Gene.'' Encyclopedia. Web. 23 December, 2020.