Dangerous Drug Interactions: Are You at Risk?

More medications and dietary supplements are available today than ever—from heart and diabetes drugs to vitamins and herbal supplements. Some certainly make us healthier. But new worries have emerged that suggest a growing number of older Americans are taking drug combinations that put them at risk for a harmful or even deadly drug interaction.

The latest alarm comes from researchers at the College of Pharmacy at the University of Illinois, who have been tracking more than 2,000 older Americans who took part in the National Social Life, Health, and Aging Project. They found that one in six older adults are at risk of a major drug-drug interaction—when one drug affects the way another drug works or modifies its effects. Some potential adverse effects include uncontrolled bleeding, kidney failure, blood clots, heart attacks, and heartbeat irregularities.

The survey group reflected a cross section of older Americans born between 1920 and 1947 across the United States, with an average age of just over 70. The researchers conducted in-home interviews with the participants during 2005 and 2006 and once again in 2010 and 2011.

Reporting in the April issue of JAMA Internal Medicine, the researchers found that the number of older adults taking five or more prescription drugs rose from 30.6 to 35.8 percent during the five-year span. The number of people regularly taking two or more daily or weekly dietary supplements climbed from 31.6 to 47 percent.

Compounding the problem

Those numbers alone wouldn’t necessarily be worrisome. But, after analyzing common combinations of pills—which include statins, nonsteroidal anti-inflammatory drugs (NSAIDs), antiplatelet agents such as aspirin and clopidogrel, and anticoagulants like warfarin—the researchers found that the number of older people at risk of a serious drug-drug interaction nearly doubled over five years—from 8.4 to 15.1 percent.

The research team spotted 93 potentially dangerous combinations, based on the 40 most commonly used drugs and supplements. Fifteen of these were potentially serious or life-threatening interactions. “The new findings sound an important warning to doctors and patients,” says Claudene George, M.D., R.Ph., assistant professor of clinical medicine and geriatrics at Albert Einstein College of Medicine in New York. “Older adults typically take more medications than younger people. Many believe that dietary supplements are safer because they are ‘natural,’ but these ‘natural’ products can cause dangerous side effects alone or in combination with prescription medications.”

Some signs that your drugs aren’t mixing well include development of a rash, fever, diarrhea, mild difficulty breathing, and a rapid or slow heartbeat. More serious reactions include seizures and anaphylactic shock. Even mild effects, such as drowsiness and dizziness, can increase the propensity for falling and injuries such as lacerations, contusions, and fractures.

Mixing too many meds

Researchers have long known that the more drugs and supplements people take, the greater the risk of hazardous interactions. And certain combinations are particularly dangerous.

Combining an anticoagulant such as warfarin with aspirin or omega-3 fish-oil capsules, which both thin blood, can lead to uncontrolled bleeding. Combining amlodipine (which improves blood flow) and clopidogrel bisulfate (which inhibits clotting) can be hazardous to patients with heart failure.

Over the study’s five-year span, the number of older people taking several classes of prescription drugs linked to dangerous interactions rose significantly—including statins for cholesterol, antiplatelets to prevent blood clots, and proton pump inhibitors for gastroesophageal reflux disease. During this time, aspirin use rose from 30.2 to 40.2 percent. The percentage of people taking omega-3 fish oil surged from 4.7 to 18.6 percent, while vitamin D use increased from 4.6 to 15.6 percent.

Prescriptions were dispensed according to current clinical practice guidelines for the patients’ conditions. When taken alone—according to recommendations and after considering the patient’s overall health—a prescribed drug should typically be safe. However, once drugs prescribed for other conditions and over-the-counter (OTC) supplements are added, the combinations may result in significant harm.

Other factors are also likely to contribute to the severity of drug interactions, including a patient’s kidney and liver function, the drug dosages and frequency, and the type of interaction. Also, since older adults metabolize drugs less efficiently than younger people, they’re more susceptible to drug-drug interactions.

According to the study, increased drug use may have been brought about by the implementation of Medicare Part D, the approval of new drugs over the years, changes in treatment guidelines, and the availability of more generics and OTC versions of many commonly used drugs.

Dangers of don’t ask, don’t tell

Many doctors aren’t aware of the hazards their older patients face, research suggests. In a letter published in the same issue of JAMA Internal Medicine, researchers at the University of Minnesota reported that among 7,493 people who participated in the National Health Interview Survey, more than 42 percent admitted that they neglected to tell their doctors about the complementary and alternative medicine (CAM) they used. Twenty-five percent specifically didn’t mention herbs and dietary supplements, which may interact with prescription and OTC drugs.

“Both patient and physician should play an active role. Patients should inform their doctors of all medications, supplements, herbal agents, and ‘natural’ products taken. Physicians should ask patients about the use of these agents,” George says. Garlic pills, for example, may sound harmless. But, if combined with the blood-thinning drug warfarin, they can result in hemorrhaging complications.

Past surveys found that patients didn’t mention supplements to their doctors because they were concerned they might disapprove of OTC preparations. But, the University of Illinois team reported that more than half of respondents said they didn’t speak up because their doctors never asked. 

The most commonly used dietary supplements reported in the survey were multivitamins and minerals and calcium.

Lowering your risks

It’s in your best interest to do whatever you can to avoid risks associated with common drug combinations. Heed these tips:

• Establish a relationship with a primary care physician who will regularly review all your medications, including OTC drugs and supplements.

• Compile a list of all your prescription and OTC drugs and supplements—and their dosages—even those you use only occasionally. Present this regularly updated list to each of your providers.

• Consider requesting a “brown-bag review,” when you gather all your drugs and supplements in their original containers and bring them to your appointment for your doctor to examine.

• Ask your doctor to review your drugs (particularly if you take multiple prescription drugs) to make sure you still need each one.

• Ask your doctor’s advice about dietary supplements. Some may be worth taking, while many others offer little benefit and can be risky combined with prescriptions.

• Ask your doctor and your pharmacist_ about side effects and possible interactions among the pills you take.

• Use only one pharmacy for your prescriptions so they can be tracked and flagged for possible drug interactions.

• Alert your primary care doctor whenever one of your providers prescribes a new drug.

• Talk with your doctor or pharmacist about potential interactions before you start a new OTC drug or dietary supplement.

“The growing number of medications available to us can help people live longer and healthier lives, but only if they are used wisely,” George says. “Medical care is increasingly complex. Doctors, pharmacists, and patients must work together to minimize the risks for patients on multiple medications.”

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HealthAfter50 was published by the University of California, Berkeley, School of Public Health, providing up-to-date, evidence-based research and expert advice on the prevention, diagnosis, and treatment of a wide range of health conditions affecting adults in middle age and beyond. It was previously part of Remedy Health Media's network of digital and print publications, which also include HealthCentral; HIV/AIDS resources The Body and The Body Pro; the UC Berkeley Wellness Letter; and the Berkeley Wellness website. All content from HA50 merged into Healthcentral.com in 2018.