In medicine, one size does not fit all. Two people suffering from the same disease may be given the same drug, yet react quite differently. Pharmacogenetics is the extremely exciting new field of medicine that asks why.Each of us has a unique genetic make-up. It is this gene variation that can lead to different responses to medication. Pharmacogenetics examines these inherited differences in genes, which then dictate our body's responses to drugs, and it explores the ways in which these variations can be used to predict whether we will respond well or not to a particular drug. The potential of pharmacogenetics can lead to not only safer drugs, but also will enable physicians to tailor their treatments in a scientifically targeted way to be more successful for each individual patient on the first try. Why is there a need for such a field? A 1998 study of hospitalized patients published in the Journal of the American Medical Association reported that in 1994, there were 2.2 million cases of serious reactions and 100,000 deaths due to adverse drug reactions. This was not necessarily due to bad medicine. There was and still is simply no good way to predict which drug is most appropriate for each individual case. How exactly will understanding gene variation be used to predict your response to a particular drug? Currently, scientists are racing to catalog as many genetic variations as possible. 99.9% of all human genes are actually identical. The other 0.1%, making each of us unique, is made up of three million Single Nucleotide Polymorphisms, or "SNP"s. A single SNP is a variation of one nucleotide between the DNA sequences of individuals. Pharmaceutical companies and academic institutions, together with the Wellcome Trust, have set up the SNP Consortium to better understand and compile these variations. It is these variations that are at the heart of understanding any individual's response to drugs, and therefore SNPs can be used as a diagnostic tool to predict how you or I will react to a given drug. However, in order for SNPs to be used for this purpose, an individual's DNA must be examined and sequenced for the presence of specific SNPs. The problem is that currently, this process is slow and expensive. Ultimately, as technology and therefore the cost and efficiency in evaluating SNPs evolves, doctors will be able to sequence a patient's DNA and look for these SNPs in a quick, affordable, and routine way right in their office. This will give the doctor an indication of a patient's response to a specific drug, prior to prescribing it. How will this affect the care you receive from your doctor? In the future, physicians may use "SNP-chips", tiny microarrays designed to detect your own unique collection of SNPs. Your DNA will be washed over the chip and, with computer analysis, your doctor will know which gene variations you carry, which diseases you are predisposed to, and which medications you may best respond to. So picture yourself one day, possibly soon, entering your doctors office, having a simple, rapid DNA test, and enabling your doctor to select precisely the correct drug the first time, avoiding trial and error, avoiding serious side effects, and helping you get better much sooner. If this new technology has downside risks, they concern the ethical issues of just who will have access to your DNA code and thus knowledge of your future risk of getting particular diseases. Your insurance company? Your employer? Your government? How about your family, or potential spouse? This raises far too many legal and ethical issues for today's column… Welcome to the future of medicine. As always, the best of health to you all! Dr. Alan Frischer is former chief of staff and current chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.
********** Published: May 22, 2009 - Volume 8 - Issue 5