Drug Interactions: How to Avoid Them


Older people often have more health problems and take more medications than younger people. As a result, older adults are at increased risk of harmful interactions between different medications. The University of Michigan National Poll on Healthy Aging asked a national sample of older adults age 50–80 about their experiences and beliefs related to prescription medications and drug interactions.

Medication Use and Pharmacies

Most adults (63%) reported taking two or more prescription drugs, with 16% taking six or more. To fill these prescriptions, 21% of older adults have used more than one pharmacy in the past two years. This includes respondents using a combination of mail-order and retail pharmacies, as well as those who filled prescriptions at more than one retail pharmacy.

The majority of respondents chose among different pharmacy options based on price (29%) or convenience (81%). However, in some cases, the choice of pharmacy was limited due to insurance restrictions, prescriptions being sent electronically to a certain pharmacy, or a medication not being available at the person’s usual pharmacy.

Most adults (79%) felt that retail and mail-order pharmacies were about the same in terms of medication quality. In terms of helping older adults know how to take their medications, 50% felt retail and mail-order pharmacies were equivalent, while 48% said retail pharmacies were better.


Avoiding Drug Interactions

Respondents varied in their beliefs about who is responsible for talking with them about possible drug interactions. Eleven percent said the pharmacist is responsible, 26% said the doctor is responsible, and 63% believed that the doctor and pharmacist are equally responsible.

Complicating the discussion of possible drug interactions is that respondents often see multiple doctors (69%) and use multiple pharmacies (21%). Only 36% of adults said the pharmacist definitely knows about all their medications when they fill a prescription; another 40% thought the pharmacist probably had that information.

The majority of older adults (90%) were confident that they know how to avoid drug interactions (21% very confident and 69% mostly/somewhat confident), while 10% were not confident. Despite the overall high level of confidence, only 35% of adults had talked with someone about drug interactions in the past two years, most often a doctor (75%), pharmacist (60%), or nurse (14%). This proportion was slightly higher among respondents taking six or more medications, with 44% reporting that they had discussed drug interactions with someone.


Prior research suggests that about one in six adults 65 and older will experience a harmful reaction to medication. Findings from this National Poll on Healthy Aging provide some insights into how older adults think about avoiding drug interactions.

Most respondents felt that both doctors and pharmacists share responsibility for talking with them about possible drug interactions. With the expansion of electronic health records (EHRs) and electronic prescribing systems, physicians and pharmacists have tools that will alert them to potential drug interactions.

Challenges arise, however, when older adults fill prescriptions at more than one pharmacy, or receive prescriptions from multiple providers who are not all using a shared EHR system. In these situations, alert algorithms are less accurate because they may be missing key pieces of information. In addition, many older adults use over-the-counter medications and supplements, some of which may pose a risk of drug interactions; however, information about over-the-counter and supplement use may not be included in electronic drug alert systems.

The majority of poll respondents reported that they had not spoken to anyone about drug interactions in the past two years. This suggests that providers and pharmacists may not be informing patients, in easy to understand language, that a medication review has been done. Providers and pharmacists need to actively engage patients and their families in education around their medications, what types of interactions might occur, and how to avoid interactions.

Older adults also need to be proactive partners in avoiding drug interactions. They should keep an updated list of all medications—both prescription and non-prescriptions, as well as supplements and vitamins. By bringing this list of medications and dosages to appointments and to the pharmacy, older adults can assist providers and pharmacists to more accurately assess the potential for drug interactions.

Finally, older adults should ask providers and pharmacists what kinds of side effects medications can cause, and what to do if they think they are having a medication-related side effect. If they experience a reaction or if they feel a medication is not working, older adults may simply stop taking their medications, which also could pose harm. Specifically counseling patients about what to do in the event of a possible medication-related problem can help to avoid these situations.

Data Source and Methods

This National Poll on Healthy Aging report presents findings from a nationally representative household survey conducted exclusively by GfK Custom Research, LLC (GfK), for the University of Michigan’s Institute for Healthcare Policy and Innovation. National Poll on Healthy Aging surveys are conducted using GfK’s KnowledgePanel®, the largest national, probability-based panel in the U.S. Surveys are fielded two to three times a year with a sample of approximately 2,000 KnowledgePanel® members age 50–80.

This survey was administered online in April 2017 to a randomly selected, stratified group of older adults age 50–80 (n=2,131). Respondents were selected from GfK’s web-enabled KnowledgePanel® which closely resembles the U.S. population. The sample was subsequently weighted to reflect population figures from the U.S. Census Bureau.

This report is based on responses from 1,690 respondents age 50–80 taking one or more prescription drugs. The completion rate was 77% among panel members contacted to participate. The margin of error is ±2 to 4 percentage points for all outcomes included in this report.

Findings from the National Poll on Healthy Aging do not represent the opinions of the University of Michigan. The University of Michigan reserves all rights over this material.


Clark S, Solway E, Singer D, Kirch M, Malani P. Drug interactions - How to avoid them. University of Michigan National Poll on Healthy Aging. December 2017. Available at: http://hdl.handle.net/2027.42/139881

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December 2017
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