WHAT IS CYP450?
Cytochrome P 450 (CYP-450) genotyping test is a genotyping test that is used to find out how your body processes or metabolizes a drug. Our body uses the cytochrome P450 enzyme system to process medications.
Cytochrome P450 (CYPs) are a super-family of enzymes that contain heme as a cofactor and function as mono-oxygenases. Due to inherited traits that cause variation in Cytochrome P450 enzymes, the effect of medications on individuals will be felt differently. Cytochrome P450 function is the metabolizing harmful substrates like a toxin.
A CYP450 genotyping assay is aimed at looking for changes or variations in these genes (that is, to test cross genotype) that reveal whether a certain medication could be used as an effective treatment for you, or whether side effects can be associated with a specific medication.
Drug-gene testing (also known as pharmacogenomics or pharmacogenetics) is the study of how genes affect your body’s response to medication.
Among the cytochrome P450 enzymes, is the CYP 2D6 enzyme, which processes many antidepressants and antipsychotic medications.
USES OF CYTOCHROME P 450 GENOTYPING TEST
The role of Cytochrome P450 genotyping assay includes:
- Checking your DNA for certain gene variations.
- To know how your body can respond to particular antidepressants.
- Identification of variations in other enzymes like the CYP 2C19 enzyme.
- Identification of antidepressants best for you (with fewer side effects).
- Checking whether tamoxifen is likely to be more effective for breast cancer.
- To know the appropriate dosing of the blood thinner warfarin to reduce the risks of adverse effects.
PROCEDURE FOR CYTOCHROME P450 GENOTYPING TESTS
Using one of the following methods, a sample of your DNA is taken. You do not need to fast or have special preparation.
Anyone out of the following types of procedure may be used:
- Cheek Swab
Rub a cotton swab inside your cheek to get a cell sample.
- Saliva Collection
Spit your saliva into a collection tube.
- Blood Test
A lab technician will draw blood from a vein in your arm, for use.
Few minutes will be needed to take the DNA sample. Then your sample is forwarded to a lab where your DNA is analyzed for specific genes.
The result for the cytochrome P450 genotyping test may take 5─7 days to get. On getting the results, your doctor will discuss the result with you, as well as your treatment options. CYP 450 genotyping assay can highlight how well your body processes a drug by looking at specific enzymes.
The results are categorized according to the rate at which cytochrome P450 metabolism of a specific medication occurs in your body. A Cytochrome P450 genotyping test result indicates which of the following four types applies to you:
- Poor Metabolizers
If a certain drug is processed more slowly than normal due to a missing enzyme, the drug can build up in your system, which can increase the possibility of side effects. However, you might still be able to benefit from these medications, but at lower dosages.
- Intermediate Metabolizers
When there is reduced enzyme function in processing drugs, you may not process some medications as effective as do people who are classified as normal metabolizers.
- Normal (Extensive) Metabolizers
If it is indicated that you process certain antidepressants normally, you’re more likely to benefit from treatment with fewer side effects than people who don’t process those medications as effective.
- Ultra-rapid Metabolizers
Medications leave your system too quickly. They are left with no chance to work properly. In this situation, you will likely need higher-than-usual doses of medications.
EXAMPLES OF CYTOCHROME P450 DRUGS, ENZYMES, AND SUBSTRATES
The Cytochrome P450 system comprises the following enzymes:
- The CYP 2D6 enzyme, which includes:
- Metabolizes antidepressants such as:
- Fluoxetine (Prozac).
- Paroxetine (Paxil, Pexeva).
- Fluvoxamine (Luvox).
- Venlafaxine (Effexor XR).
Tricyclic antidepressants such as:
- Nortriptyline (Pamelor).
- Clomipramine (Anafranil).
- Desipramine (Norpramin).
- Imipramine (Tofranil).
Some antidepressants, such as fluoxetine and paroxetine, can cause the CYP 2D6 enzyme to slow down.
The CYP 2C19 enzyme, which includes:
- Citalopram (Celexa).
- Escitalopram (Lexapro).
This is one of the drugs metabolized by multiple enzymes. It is metabolized by CYP IA2, CYP 2D6, and CYP 3A4.
LIMITATIONS OF CYP 450 GENOTYPING TESTS
Despite all the usefulness of the CYP 450 genotyping assay, there are still limitations such as:
- Inability to predict which medication is the best for you since the tests only give clues.
- Availability to only certain medications.
- Specificity of test to a medication.
- Change in medication may require another test.
- Concentration on how the body metabolizes a drug, not on the effect of the drug (for instance, the drug may change the brain receptors to improve on symptoms).
- Focus on activities of only some of the genes involved in how your body uses certain drugs.
- Partial clarity in how useful the tests are in choosing antidepressants, because despite the tests, you may still need to try other antidepressants and different doses, to identify which one works best for you.
- Some insurance companies don’t cover the costs of these tests.
Doctors use CYP 450 tests and see them as useful tools in helping to arrive at clinical decisions. Cytochrome P450 genotyping tests are just tools that may help in finding out how your body metabolizes a drug. Antidepressants can be tried based on your medical history and symptoms, which are standard methods for identifying the best medications for your health condition or status.
- Where are Cytochrome P450 enzymes found?
In human beings, cytochrome P450 enzymes are found within the endoplasmic reticulum and mitochondria of the liver cells. They are found in many other cells of the body. As mentioned earlier, these membrane-bound proteins are involved in the metabolism of many harmful substrates like toxins.
- Why are they called CYP 450?
CYP 450 is so-called because they are bound to membranes within a cell (cyto) and contains a heme pigment (chrome + P) that absorbs light at a wavelength of 450mm when exposed to carbon monoxide. The drugs which cause CYP 450 drug interactions are referred to as either inhibitors or inducers.
- What do CYP 450 enzymes do?
Cytochrome P450 enzymes function as mono-oxygenases. In mammals (human beings, for example), they oxidize steroids, fatty acids, and xenobiotics. They are necessary for clearing various compounds, as well as for hormone synthesis and breakdown.
- Is cytochrome of only one type?
Cytochromes are classified into four types: A, B, C, and D; based on the kind of heme they possess as the prosthetic group.
- What does cytochrome mean?
Cytochromes are any of the several intracellular hemoprotein respiratory pigments that are enzymes functioning in electron transport, as carriers of electrons.