The goal of taking any medication is to deliver a sufficient dose to produce the desired effect at the right location in the body. But each body is different and often people respond differently to the same medication. Pharmacogenomics – part of the growing field of personalized medication -- addresses this widespread problem.
Pharmacogenomics is the study of matching drug therapy to an individual’s genetic profile in the hopes of avoiding serious side effects and boosting effectiveness.
Genetic variability is one reason people respond differently to the same medication. Gene variations affect how quickly or slowly a medication is metabolized as well as the medication’s ability to have the desired effect.
For example, the FDA recently introduced new labeling for the drug warfarin (Coumadin) that reflects pharmacogenomics. Warfarin prevents blood clots, but too high a dose can lead to life-threatening bleeding. Doctors typically use a patient’s age, gender, weight, and medical history to estimate an appropriate starting dose and then modify the dose after blood tests show the extent of blood thinning. But research now shows that tests for certain gene variations may offer valuable information, too.
The warfarin label now states that a lower starting dose should be considered in people with variations in the following two genes— CYP2C9 and VKORC1. Variants of CYP2C9 slow the metabolism of warfarin; variants of VKORC1 make the body more sensitive to warfarin. Blood tests are available to detect these gene variants.
Personalized medication is already well established for certain cancer medication, like trastuzumab (Herceptin). This medication is only effective in women whose breast cancer cells have a specific genetic variation that results in the overproduction of the protein Her2. Women are tested for this variation before the medication is prescribed.
