Mixing Supplements and Prescription Drugs Carries Potential Risks

By May Wilkerson 04/01/16

More than 15% of older Americans are at risk of a harmful drug reaction by taking dietary supplements alongside prescription medications. 

Mixing Supplements and Prescription Drugs Carries Potential Risks
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Dietary supplements, like vitamins and amino acids, are growing in popularity in the U.S. And so are prescription drugs. From 2006 to 2011, the number of older Americans (ages 62 to 85) taking five or more prescription medications or supplements rose from 53.4% to 67.1%. But mixing the two classes of substances can lead to some dangerous side effects, a new study has found. For example, warfarin, a common prescription blood thinner, when combined with omega-3 fish oil, a popular supplement, can increase the risk of heart disease in some patients.

Using a database of drug interactions, researchers examined the 20 most common prescription drugs and supplements used by participants in their study and whether these substances were predicted to have adverse side effects when combined. They found that 16 combinations of prescription medications, over-the-counter drugs and supplements were predicted to raise the risk of negative side effects. The most common side effect was bleeding. During the study period, the number of adults taking one of these combinations nearly doubled from 8.4% to 15.1%, according to the results, published this week in the journal JAMA Internal Medicine.

The lead author of the study, Dima M. Qato, assistant professor of pharmacy systems, outcomes and policy at the University of Illinois at Chicago, told CNN that though it's important to improve access to essential medications, "we are not prioritizing enough how safe these medications are in the context of all the prescription and nonprescription medications older adults are using." 

The researchers were surprised by just how popular supplements, especially omega-3 fish oils, have become—the number of participants taking omega-3s rose from 4.7% in 2005 to 18.6% in 2011. Though they are often touted as being good for heart health, Qato said there's no evidence that omega-3s benefit cardiovascular health. 

So what can be done to lower the risks? Many pharmacies have databases in place to alert pharmacists about potentially harmful drug interactions. But these databases overlook prescriptions filled at other pharmacies, as well as over-the-counter medications and supplements. Doctors not only need to better informed about the cocktail of medications their patients are on, but they should also be provided more comprehensive information about potential drug interactions, said Qato.

Another study found that doctors are often unaware of any nonprescription drugs their patients are taking. In 2012, 24.9% of patients did not tell their doctor that they were taking a supplement or herb, usually because the doctor didn’t ask or the patient didn’t think it was important. 

"The message for doctors is that we need to be more proactive about asking patients about things going on in their lives and the different therapies they're using," Dr. Michael Steinman, professor of medicine at the University of California-San Francisco, told CNN. "And there's really a lesson in there for patients, that it is really useful for doctors to know which therapies you're taking, even if they're things the doctor didn't prescribe."

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May Wilkerson is a writer, comic and Managing Editor @someecards. Co-host of the podcast Crazy; In Bed w/alyssalimp. She is also the top Google result for "insufferable lunatic." Follow this insufferable lunatic on Twitter.