Adverse drug reactions, (ADRs) usually called side effects, are a long-standing and largely neglected major medical problem. These are not medical errors and occur within the FDA or INFARMED or any other regulatory national board approved dosage and labeling recommendations. The recently reported problems with antidepressant induced teen suicides, the recalls of Vioxx and Baycol shows some of these problems.

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.

Approximately half of the world population has 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.
• 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 METABOLIZER. 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 use of DNA drug reaction testing or pharmacogenetic testing has the potential to save tens of thousands of lives, prevent hundreds of thousands of serious events that initiate or extend hospital stays, and save hundreds of millions of euros in health care costs.

Who should be tested? Everyone that is considering taking a particular medication should be tested but in particular the elderly and children should do this test.

Testing the Elderly

Elderly patients have a decreased capacity to detoxify drugs they are taking. Drug interactions are also an important contributor to adverse drug reactions, which makes the aging population vulnerable because of the large number of drugs they are taking.

Testing Children

Few drugs are tested in children prior to release. Many are used off label in pediatric populations. For example, only Prozac (fluoxetine) has been approved for use in children, yet many others are prescribed off label. While the rate of adverse drug reactions in children is lower than in adults, children with severe medical conditions are the most affected.

To read further on the advantages of our pharmacogenetic test please click here.