Background: Why Pharmacogenetics is Changing Medicine
"We used to think the future was in the stars. Now we know it is in our genes."James Watson
1962 Nobel Prize Laureate
In only 30 years, the science of genetics has come an amazing distance. With the first descriptions of DNA came wonderment that a string of four seemingly simple molecules could hold all of the information needed to make a human being, or a marigold, or a portabello mushroom. The idea that the total number of human genes is much less than we thought (around 34,000) illustrates a titanic truth: Individuality is caused by a collection of small differences in the DNA. These differences are called "variants."
Variations in DNA determine hair color, the tone of your voice, and how well you digest spicy foods. A few variants determine how we respond to drugs. The study of those particular variations is called "Pharmacogenetics." This term is a combination of pharmaceutical and genetics.
The term "Pharmacogenetics" was first used in medical publications in the mid-1950s. Anesthesiologists, whose job it is to sedate people for surgery, noticed that members of some families seemed to react differently to particular drugs. To account for what were apparently genetic (inherited) differences, physicians started to delve deeper into family medical histories before prescribing certain drugs.
More recently, with the rapid pace of discovery in genetics and the availability of a map of the human genome, genetic variants and their influence on the medical effectiveness of drugs has become a major area of scientific research. These variants often occur in enzymes that are not used for normal metabolism or everyday physical function, but that become a factor when the body is metabolizing medications.
Certain variants, for example, indicate that a person will metabolize a drug more slowly than normal. That drug, prescribed in a standard dose, could build up in the patient's system and eventually cause symptoms of overdose.
Another patient with another set of variants might metabolize a drug more quickly than normal. A standard dose, in this case, would flush so quickly out of the patient's system that it would never reach a level sufficient to have the desired effect.
By using pharmacogenetic testing to know and understand key genetic variables, it is now possible for physicians to predict how specific patients will react to drugs, and to prescribe from the outset the dosage necessary for the greatest therapeutic effect. This could save time, money and - most importantly - the suffering associated with Adverse Drug Reactions (ADRs).
For detailed scientific background on the origins of pharmacogenetic testing, click here.