Drug Reaction Testing

Do not alter the dosage amount or schedule of any drug you are taking without first consulting your medical provider or pharmacist.

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Genelex will be happy to mail information to you or to your healthcare provider on your behalf, simply complete the request form.

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Research shows that of all the clinical factors such as age, sex, weight, general health and liver function that alter a patient's response to drugs, genetic factors are the most important. This information becomes even more crucial when you consider the fact that adverse reactions to prescription drugs are killing about 106,000 Americans each year -- roughly three times as many as are killed by automobiles. This makes prescription drugs the fourth leading killer in the U.S., after heart disease, cancer, and stroke.

We currently offer CYP2D6, CYP2C9, CYP2C19, NAT2 and CYP1A2 screens that can help your physician or pharmacist predict your particular response to many prescription, OTC (over-the-counter) and herbal medicines including those used to treat depression, anxiety, seizures and psychoses; blood pressure, anticoagulation and other heart medicines; anti-diabetic agents, and many pain relievers. These include such important medications as Coumadin (warfarin), Prozac, Zoloft, Paxil, Effexor, hydrocodone , amitriptyline, Claritin, cyclobenzaprine, Haldol, metoprolol, Rythmol, Tagamet, tamoxifen, Valium, carisoprodol, diazepam, Dilantin, Premarin, and Prevacid (and the over-the-counter drugs, Allegra, Dytuss and Tusstat). Click here to view a more complete list of drugs processed through these pathways.

Approximately half of all Americans have genetic defects that affect how they process these drugs. There are four different types of metabolizers, and we all fall into one of these categories for the variable pathways in Cytochrome P450 (this Cytochrome is responsible for creating the enzymes that process chemicals of all kinds through our bodies.) The easiest way to understand this is to picture a two lane highway.

· If you are the first type which is the norm, you would be an EXTENSIVE metabolizer. Both lanes of the highway are open and moving. Medications prescribed in normal doses will be metabolized by your body.

· If you are the second type, you would be an INTERMEDIATE metabolizer. This means that one lane of that highway is open and moving and the other lane is not, causing you to metabolize the medications more slowly. In this case you will need a lower dosage, and there is a chance of medications building up in your system causing adverse effects. It is especially important to monitor medications if you are in this category.

Intermediate metabolizers through the 2C9 pathway, for instance, have an increased risk of bleeding incidences when taking the common blood thinner Coumadin or warfarin. For this reason, a recent article in the Journal of the American Medical Association states that screening for CYP2C9 variants may reduce the risk of adverse drug reactions in these patients.

· The third type is a POOR metabolizer. In this case both lanes of the highway would be stopped. There is a possibility that alternate routes can be found, but this type of metabolizer is potentially very dangerous, as there is a great chance for the medication to build up in your system making you very sick, or even killing you.

For example, a poor metabolizer of phenytoin, a common antiepileptic would not be able to process the drug and would actually have an increased rather than decreased risk of seizure if prescribed this drug.

· The fourth type of metabolizer is ULTRA EXTENSIVE. This means you have additional lanes for processing, picture an Indy 500 speedway. In this instance, you literally burn through medications. If you were an Ultra extensive metabolizer through the 2D6 pathway and while in surgery and your doctor gave you codeine as a pain killer, you would receive no pain relief because the codeine would be metabolized so fast that it would have little or no effect on you.

The Testing Process

The process is simple. We send you a cheek swab collection kit in the mail. Samples are returned to our laboratory and results are typically available in 10 business days. STAT testing is available with a five-day turnaround for an additional fee.

Currently Available Tests

CYP2D6 (cytochrome P450 2D6) is the best studied of the DMEs and acts on one-fourth of all prescription drugs, including the selective serotonin reuptake inhibitors (SSRI), tricylic antidepressants (TCA), betablockers such as Inderal and the Type 1A antiarrhythmics. Approximately 10% of the population has a slow acting form of this enzyme and 7% a super-fast acting form. Thirty-five percent are carriers of a non-functional 2D6 allele, especially elevating the risk of ADRs when these individuals are taking multiple drugs. Drugs that CYP2D6 metabolizes include Prozac, Zoloft, Paxil, Effexor, hydrocodone , amitriptyline, Claritin, cyclobenzaprine, Haldol, metoprolol, Rythmol, Tagamet, tamoxifen, and the over-the-counter diphenylhydramine drugs, Allegra, Dytuss, and Tusstat. CYP2D6 is responsible for activating the pro-drug codeine into its active form and the drug is therefore inactive in CYP2D6 slow metabolizers.

CYP2C9 (cytochrome P450 2C9) is the primary route of metabolism for Coumadin (warfarin). Approximately 10% of the population are carriers of at least one allele for the slow-metabolizing form of CYP2C9 and may be treatable with 50% of the dose at which normal metabolizers are treated. Other drugs metabolized by CYP2C9 include Amaryl, isoniazid, ibuprofen, amitriptyline, Dilantin, Hyzaar, THC (tetrahydrocannabinol), naproxen, and Viagra.

CYP2C19 (cytochrome P450 2C19) is associated with the metabolism of carisoprodol, diazepam, Dilantin, and Prevacid.

CYP1A2 (cytochrome P450 1A2) is associated with the metabolism of amitriptyline, olanzapine, haloperidol, duloxetine, propranolol, theophylline, caffeine, diazepam, chlordiazepoxide, estrogens, tamoxifen, and cyclobenzaprine.

NAT2 (N-acetyltransferase 2) is a second-step DME that acts on isoniazid, procainamide, and Azulfidine. The frequency of the NAT2 "slow acetylator" in various worldwide populations ranges from 10% to more than 90%.

The advantages of Genelex's consumer genetic testing include:

· Safety. Decrease the chance that you will be the victim of an adverse drug reaction. More than 100,000 hospitalized Americans die of adverse drug reactions and two million outpatients have serious episodes each year. Knowledge of your DNA Drug Reaction Profile may help your physician or pharmacist prevent this from happening.

· Efficacy. Prescription drugs on the market today are usually prescribed by trial and error because they have been tested and approved in a "one size fits all" fashion. If you eliminate a particular drug more rapidly than the norm, taking the normal dose may be a complete waste of time. The drug simply will not work as prescribed, and it may take a while to discover this.

· Responsibility. Play a more active role in your health, your family's health, and in healthcare at large. DNA testing for drug reactions is just coming onto the market and you, the consumer, can help all of us take this major step toward better medicine.

Call Genelex today at 800-523-3080 to order testing, order on-line, or download the order form and fax or mail in your order. Don't forget to take a look at our other informational genetic testing products now as you receive significant discounts when ordering tests at the same time.

Check Common Drugs Processed by Enzymes We Test

Order on-line by clicking here

Michael's tragedy could have easily been avoided had he been tested beforehand to see which variants of the CYP2D6 gene he carried. The DNA Prescription Drug Reaction Profile offered by Genelex tests this drug metabolizing enzyme.

After Michael died, we found out that there were tests to spot enzyme deficiencies that can cause adverse drug reactions. I felt devastated when I heard that. It should be the norm that the tests are used whenever there are concerns about possible side effects.
— Jayne Adams-Conroy, mother of ADR victim

Disclaimer The content of this web site is for public use, free of charge, and for information only. It is not intended to be used in any other way. The authors disclaim any liability, loss, injury, or damage incurred as a consequence, directly or indirectly, of the use and application of any of the content of this web site. The information presented on this site is intended as general health information and as an educational tool. It is not intended as medical advice. Only a physician, pharmacist, or other healthcare professional should advise a patient on medical issues and should do so using a medical history and other factors identified and documented as part of the health professional/patient relationship.

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