How does pharmacogenomics work in practice?

An example of pharmacogenomics in treatment decisions is the use of a blood-thinning drug called warfarin (Coumadin, Jantoven). If you have a blood clot, your treatment may include a prescription for warfarin to treat the current clot and to prevent additional blood clots from forming.

Your doctor's goal is to prescribe a dose that will be strong enough to prevent blood clotting but not strong enough to cause adverse reactions, such as internal bleeding (hemorrhaging). The window for the effective and safe dose of this drug for any person is relatively narrow.

Dosage has traditionally been based on such factors as weight, age, and kidney and liver function, as well as a laboratory test to assess the blood-thinning effect of the drug in each person. The dosing guidelines, although valuable, may have limited value in predicting the outcome for every person.

In the early 2000s, studies comparing treatment outcomes with genomic data revealed that genetic variation was associated with either an increased risk of hemorrhaging or with the need for a higher dose to be effective.

Because of these findings, your doctor may use your genomic information to help guide treatment decisions. A tissue sample swabbed from inside your cheek or a blood sample provides cells for a laboratory test to decipher your genome.

Based on the results, your doctor may judge more accurately what dose of warfarin is likely to be safe and effective for you or whether warfarin is even an appropriate treatment option.

The future of pharmacogenomics

Although pharmacogenomics has much promise and has made important strides in recent years, it's still in its early stages. Clinical trials are needed not only to identify links between genes and treatment outcomes but also to confirm initial findings, clarify the meaning of these associations and translate them into prescribing guidelines.

Nonetheless, progress in this field points toward a time when pharmacogenomics may be part of routine medical care.

June 05, 2015 See more In-depth