Recent Article in JAMA Underscores Need for Pharmacogenetics
On March 21, an article published online in JAMA Internal Medicine examined changes in the prevalence of medication use and the frequency of major drug-drug interactions. The study was authored by Dima M. Qato, PharmD, MPH, PhD of the Department of Pharmacy Systems, Outcomes, and Policy at the University of Illinois at Chicago, and colleagues.
In-home interviews, with direct medication inspection, were conducted in 2005 to 2006, and again in 2010 to 2011 to determine patterns of medication use. This included types of medication (e.g., prescription, over-the-counter, and dietary supplements), as well as concurrent use (e.g., regular use of at least two medications). The use of at least one prescription medication saw an increase from 84.1% in 2005-2006 to 87.7% in 2010-2011. This statistic alone provides some argument for pharmacogenetics – roughly 60-75% of medications utilize the cytochrome P450 enzymes for drug metabolism. More importantly, however, the study found that the proportion of elderly patients using five or more prescription medications concurrently rose from 30.6% to 35.8% during that five year period. And this increase was not limited to only prescription medications; the proportion of those using five or more medications or dietary supplements of any type increased from 53.4% to 67.1%.
With this rise in medication use and polypharmacy comes a rise in risk for major drug-drug interactions. The study by Qato et al. found that the proportion of older adults using combinations of medications with the potential for major drug-drug interactions was 15.1% during the 2010-2011 period, almost double the rate of 8.4% during the 2005-2006 period. And this only accounts for drug-drug interactions. Drug-gene and cumulative drug and gene interaction risk was not measured in this study and represents over half of significant interaction risks. With roughly 90% of people having detectable DNA variations that can affect how drugs are metabolized, this large increase in polypharmacy gives all the more reason to begin implementing pharmacogenetic testing more broadly in our healthcare systems.
This study invited commentary from Dr. Michael Steinman, from the University of California, San Francisco’s Geriatrics Division in the Department of Medicine. The commentary is titled, “Polypharmacy – Time to Get Beyond Numbers.” In his commentary, Dr. Steinman notes that what these numbers cannot tell us, are whether the changes are good or bad. As he says, “some of the biggest increases documented by Qato et al. were in the use of statins and vitamin D. Is this appropriate therapy or overtreatment?” The question of proper therapy or overtreatment is indeed a big one.
We may not be able to ultimately answer the question of “how much medication is too much,” but there are tools available to make sure that fewer problems arise from medication regimens, one of these being pharmacogenetic testing. Drug metabolizing enzyme testing will detect significant variations that may alter the way drugs are processed and thus help providers to prescribe more accurate doses or different medications entirely. To make testing even more powerful, phenotype results from drug sensitivity testing can be imported into YouScript software for interpretation where adding a list of current medications – and even medications that are in consideration for future prescribing – will give real time feedback on any interactions detected. And the interactions are not just limited to drug-drug interactions; YouScript’s algorithms can predict potential drug-gene and cumulative drug-drug gene interactions.
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