Progressing toward prescriptions better suited to individual patients

What if a drug that works for most people turned toxic in your body because of your genetic makeup? What if your genes rendered a certain medication useless while making another super-effective? It may not be too much longer before we have answers to these kinds of questions. In limited cases, we already do!
 
For most of our modern medical history, drugs have been prescribed with a “one-size-fits-most” approach, but that is starting to change. Pharmacogenetics, a major up-and-coming area in medicine, looks at how your DNA affects the way you respond to drugs. In my geriatrics department at Cleveland Clinic, for example, we are able to use pharmacogenetics to see which medications a patient might be better suited for to help with high blood pressure or heart disease. This helps us prescribe a drug and a dosage that delivers minimal side effects and maximum benefit.
 
We’ve known since the 1950s that genetics can influence a person’s reaction to medication, but it’s only very recently that there’s been enough data and research to be practically helpful for physicians like me who work with patients day to day.

Let’s say someone needs a blood thinner. We do a blood draw and get genetic information about the patient. Then we look at the drugs that have been tested. Does that person metabolize them normally? Do they need a different dose than the standard protocol, either because they metabolize it so well or because they metabolize it slowly and it stays in their system longer? This approach helps reduce risks such as excessive bleeding or muscle breakdown.
When the first breakthroughs in pharmacogenetics happened, there was a lot of excitement and anticipation that many more breakthroughs would quickly follow. Unfortunately, progress has been slower than we had hoped. Right now, we know of variations in approximately 20 genes that provide useful predictions related to somewhere around 100 drugs. This represents about 7 percent of all drugs approved by the FDA. In other words, we have a long way to go.
 
While recognizing we’re in the very early stages of this field, I’m extremely excited about the possibilities. Already, because of our application of pharmacogenetics at Cleveland Clinic, I’ve noticed an obvious reduction in side effects in my geriatric patients, and the need to change medications has dropped drastically.
 
It’s mind-blowing to think about where this could lead. If I know up front what medication to prescribe that would be just right for that particular patient, what a difference that would make for people!

RICHARD H. CARTABUKE, M.D.,
practices internal medicine and geriatrics at the Cleveland Clinic and is medical director of Healthnetwork Foundation.