How do genes affect the way drugs work?
In December 2008, the New York Times ran a story about a woman from California who had been taking a drug called tamoxifen to help prevent breast cancer. After two years of taking the drug, her doctor ordered a new genetic test that showed that her genes were preventing the drug from working properly.
“You find out you’ve been taking this medication for all this time, and find out you are not getting benefit…I was devastated” says the women. She had to stop taking tamoxifen. The good news is that she found out that the drug was not helping her and her doctor can now prescribe a drug which will work in her body. The bad news is that she could have known this two years ago if she had taken the genetic test from Day 1.
Experts report that approximately $300 billion is wasted each year on drugs which apparently do not work in people who have certain genes. These people never receive the full benefit from these drugs. Others are getting dangerous side effects.
For example, the blood-thinning drug warfarin is one of the top twenty drugs prescribed in the US. It is used to help prevent blood clots. If a person’s genes prevent the drug from working correctly, warfarin becomes dangerous. It is one of the top three drugs that cause hospitalization or emergency room visits. If a person has genes that allow too much warfarin to get into the bloodstream, the blood cannot clot correctly and the person can have bleeding. On the other hand, if a person has genes that prevent enough warfarin from getting into the bloodstream, the person could develop serious blood clots. The way a person’s body reacts to warfarin, tamoxifen and other drugs depends on differences in their genetic makeup.
Genes provide your body with instructions for making enzymes. Enzymes are needed for your body to break down drugs so your body can get benefit from the medicine. You carry two copies of every gene: one from your mother and one from your father. Differences in these genes can affect the speed of different enzymes you have in your body. This affects how well your body is able to use medicines and how well drugs work in your body. Differences in your enzymes can affect how your body can metabolize (break down) a drug and how long the drug stays your body. Based on what type of genes you carry, you may be:
- a poor drug metabolizer
If you are a “poor metabolizer”, you do not break down drugs well. This may result in too much drug in the body which may lead to a dangerous side effect or even death. In some cases, your body may not be able to break down certain drugs to their working form and therefore the drugs will not work properly.
- an extensive or “normal” drug metbolizer
You metabolize drugs at the normal rate.
- an ultra-rapid drug metabolizer
If you are an “ultra-rapid” metabolizer, this means you break down drugs too fast, causing them to be of no use in the body. If medications do not work properly, conditions such as high blood pressure, blood disorders, and cancer will be left untreated and may even lead to death.
Genetic Tests for Drug Response
Researchers have now found more than 30 types of drug metabolizing enzymes in humans and mostly all of them vary between people.
The three main genetic tests available today include: CYP2D6, CYP2C9, and CYP2C1.
Read entire article at: Consumer Health
For more information on Genetic Drug Testing
(PGx Metabolic Validation Program) contact:
PGx Medical
Individualized Care – Personalized Medicine
info@pgxmed.com
405-509-5112