Nearly three out of four U.S. adults have more than one chronic illness, and many of them are taking medications to treat their conditions. But could the medication used to treat one illness be making the other worse?

That’s the question researchers from Oregon State University set out to answer in a study published in PLOS One.

Many doctors currently use the “one at a time” approach of treating a condition—even if these treatments may conflict with one another. Looking into the prevalence of this issue, researchers found that more than 22 percent of study participants were taking at least one medication that could worsen a coexisting condition.

The term researchers used is “therapeutic competition,” and when the problem was identified, only 16 percent of the participants' cases were changed—the others continued being prescribed competing drugs.

Common conditions where therapeutic competition is found include:

  • Diabetes

  • Coronary artery disease

  • COPD

  • Dementia

  • Heart failure

  • High blood pressure

  • High cholesterol

  • Osteoarthritis

  • Depression

Competition isn’t the only concern. Sometimes use of multiple medications can lead to an increased number of side effects like dizziness, fatigue, and delirium.

“Many physicians are aware of these concerns but there isn’t much information available on what to do about it,” said David Lee, an assistant professor in the Oregon State University/Oregon Health & Science University College of Pharmacy.

Most drugs focus on a particular disease, and doctors sometimes treat people in that same way. “As a result, right now we’re probably treating too many conditions with too many medications. There may be times it’s best to just focus on the most serious health problem, rather than use a drug to treat a different condition that could make the more serious health problem even worse,” Lee says.

“Evaluating the benefits and harms of cross-disease treatment regimens in individuals with common combinations of chronic conditions should be a focus of comparative effectiveness research, as should identification of effective treatments,” the study says.

More research in this area is needed for patients and doctors to make better judgments about which health issue is of the highest concern and how to treat each illness in a way that doesn't conflict with the other. Patients who are being treated for multiple illnesses need to be informed about how well their medications will get along together.

Speak with your doctor if you are concerned that your medications may be working against you—or each other.

To learn more on this topic:
9 Tips to Manage the Most Common Side Effects of Medication
Beware of Diabetes Medication-Related Problems
Know Your Medications