CYP2C19 – Metabolizing medications

The CYP family of enzymes breaks down both toxins and medications. Genetic variants in these genes can change the way that you respond to medications.

Learn how the CYP2C19 genetic variants impact your individual response to medications.

CYP2C19: From Prilosec to Plavix

Talk with your doctor or pharmacist before making any changes to a medication that you are currently taking.


The CYP2C19 enzyme is responsible for the breakdown (also called metabolism) of several popular drugs including proton pump inhibitors (Prilosec, Nexium, Prevacid), certain anti-epileptics, and an antiplatelet drug (Plavix).

Several important CYP2C19 genetic variants impact how drugs break down, causing some people to be poor metabolizers and others to be fast metabolizers.

You can have increased side effects (depending on the medication) either from being a slow metabolizer or a fast metabolizer.  Some medications, called pro-drugs, need to break down into their metabolites for the drug to be effective. Other drugs clear your system through the use of the CYP enzymes. Thus, the effect of a variant depends on the specific medication.

Examples of interactions with CYP2C19 genetic variants:

  • A fast metabolizer taking omeprazole (Prilosec) to treat h. pylori may have an insufficient response because the drug may not remain active in the body long enough.[ref]
  • Alternatively, some drugs such as Plavix convert into their active drug state through CYP2C19. If you are a poor metabolizer, it could mean Plavix (an anticoagulant) isn't activated enough.[ref]
  • Valium (diazepam) is another common drug metabolized in part by CYP2C19 (along with the CYP3A4 enzyme). Currently, there are no official recommendations to physicians as to reducing the dosages for poor metabolizers, but there is a box warning about CYP2C19.[ref]
  • A couple of SSRI's, Celexa (citalopram), Zoloft (sertraline), and Lexapro (escitalopram), also metabolize mainly through CYP2C19.[ref]

Who is a poor metabolizer? Check your genetic data below. A wide variation exists in how this gene metabolizes these drugs.

  • Approximately 10 - 20% of Asians are poor metabolizers, as are 2 - 5% of people of Caucasian descent.
  • Up to 20-30% of Caucasians are fast metabolizers, but less than 5% of Asians are.

Here is more information on drugs that are metabolized through CYP2C19.

In addition to drug metabolism, CYP2C19 also helps to activate and break down some hormones such as progesterone.[ref]  It is involved (minor) in metabolizing melatonin[ref] and is also involved in the metabolism of estradiol.[ref]

Genetic variants that impact CYP2C19


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