The growing danger of mixing prescription drugs and supplements


— A growing number of older adults are combining multiple prescription and over-the-counter medications and supplements in ways that could lead to serious side effects, according to a new study.

From 2006 to 2011, the number of older adults (ages 62 to 85) in the United States taking five or more medications or supplements rose from 53.4% to 67.1%.

A common prescription drug, for example, is warfarin, a blood thinner. But combining it with a supplement such as omega-3 fish oils, which skyrocketed in popularity during the period of the study, increases the risk of bleeding for certain patients.

The number of older adults taking at least one prescription medication or dietary supplement rose between 2005 and 2011, while over-the-counter medications became less prevalent.

The researchers used a database of reported and predicted drug interactions to determine whether the 20 most common prescription drugs and supplements used by the participants in their study were predicted to cause an adverse reaction when taken together.

They found that 16 combinations of prescription medications, over-the-counter drugs and supplements were predicted to increase the risk of adverse reactions, most commonly bleeding. The number of adults taking one of these combinations also increased during the study period, from 8.4% to 15.1%.

“We are trying to improve access to essential prescription medications like statins that could prevent heart disease and improve survival, but we are not prioritizing enough how safe these medications are in the context of all the prescription and nonprescription medications older adults are using,” said Dima M. Qato, assistant professor of pharmacy systems, outcomes and policy at the University of Illinois at Chicago. Qato is the lead author of the study, which was published on Monday in the journal JAMA Internal Medicine.

Some Rx prices drop, fish oil popularity soars

Although doctors are better able to treat chronic conditions with the expanding number of medicines available, each time they prescribe a new medication they should ask about everything else the patient is taking. “We are often treating conditions in a silo,” Qato said.

The most common prescription meds were cholesterol-lowering Zocor (simvastatin) and blood pressure medications such as Prinivil (lisinopril) and Microzide (hydrochlorothiazide), all of which became more common during the study period. In the supplement category, along with fish oil, there was a sharp increase in the use of vitamin D and vitamin E.

The rise in prescription drugs did not come as a surprise, Qato said. In addition to many new medicines entering the market, more and more drugs are becoming available in cheaper generic versions, such as simvastatin. Medicare Part D went into effect in 2006, providing insurance coverage to older adults for prescription drugs, which could also have played a part, Qato said.

What did come as a shock to Qato and her colleagues was that so many people are taking supplements, in particular omega-3 fish oils. The number of adults taking fish oil supplements, which are touted as good for your heart, rose from 4.7% in 2005 to 18.6% in 2011. “There’s very limited evidence of their clinical benefits, and for omega-3s specifically there’s no evidence of their cardiovascular benefits,” Qato said.

Ironically, many people seem to be picking up omega-3s after they fill a prescription for a medication such as warfarin and actually increasing their risk of heart disease by combining the two, Qato said. Warfarin and omega-3 is one of the combinations that the researchers found was associated with increased risk of bleeding. And the incidence of combining them rose from 0.1% to 0.8% from 2005 to 2011.

How to reduce the risk of combining medications

Qato and her colleagues suspect the reason for the decline in over-the-counter medications from 2005 to 2011 is that many of them, such as allergy medications, became more tightly regulated and patients had to ask their pharmacists for them. “That goes to show that when you regulate meds and there are restrictions on over-the-counter medications or dietary supplements, fewer people use them,” Qato said.

However, the people who can benefit from over-the-counter medications are probably still getting them, because their doctors are writing them prescriptions or their pharmacists are giving them access, she added.

Although pharmacies can play a role in reducing the risk from combining medication, they alone cannot solve the problem, Qato said. Databases are already in place to alert pharmacists about potentially dangerous drug interactions, but they miss prescriptions that patients fill at other pharmacies and any over-the-counter drugs and supplements people take.

Changes also have to be made in terms of policy and practice, Qato said. The guidelines that advise doctors on various medications should contain more comprehensive lists of potential drug interactions, including other prescription drugs as well as nonprescription drugs.

One of the best ways to ensure patients are combining medications in a safe way would be to make sure that a patient’s entire health care team, from doctor to nurse to social worker, knows about all the drugs he or she is taking, said Dr. Michael Steinman, professor of medicine at the University of California-San Francisco.

A study that is coming out in the same issue of JAMA Internal Medicine suggests that many patients do not tell their doctors about nonprescription drugs they are taking. Researchers analyzed national survey data of adults of all ages in the United States from 2012 and found that 24.9% of them did not tell their doctor that they were taking a supplement or herb. The most common reasons for nondisclosure were that the physician did not ask, and the patient did not 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,” Steinman said. “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.”