Dec. 23, 2008 -- Four out of five older adults in the U.S. regularly take at least one prescription drug and slightly more than half take five or more prescription drugs, over-the-counter drugs, or dietary supplements, a new survey shows.
Because older people take more prescription and over-the-counter (OTC) drugs and supplements, they are most at risk for potentially dangerous and even life-threatening medication interactions.
According to one recent study, 175,000 emergency room visits each year result from drug interactions or other adverse drug events among older people.
The survey suggests that one in 25, or 2.2 million, older Americans are taking drug -- or drug and supplement -- combinations that could place them at risk.
Extrapolating from the survey results, the researchers concluded that:
- Nine out of 10 older Americans regularly take at least one prescription or OTC medication.
- Nearly half of older Americans use prescription and OTC medications or nutritional supplements.
- Almost 30% use at least five prescription drugs. The number of prescription medications increased with age.
- About half of older Americans take vitamins, calcium, or other dietary supplements.
"People tend to think the drugs and supplements they get over the counter are safer than those that require prescriptions, but that is not necessarily true, especially when they are used in combination with prescription drugs," University of Chicago professor of medicine and geriatrics Stacy Tessler Lindau, MD, tells WebMD.
Drug Interactions Examined
Lindau and colleagues analyzed data from a survey conducted to estimate the prevalence and patterns of medication use among older adults.
The survey included in-home interviews with 3,005 people between the ages of 57 and 85 drawn from a nationally representative sample of the U.S. population. The interviews were conducted between June 2005 and March 2006.
Overall, 68% of older adults who regularly took at least one prescription drug were also using OTC medications, dietary supplements, or both.
Aspirin was the most commonly used drug, taken by 28% of those surveyed, followed by the diuretic hydrochlorothiazide, taken by 15.6% of survey participants, the statin drug atorvastatin (Lipitor), taken by 13.4%, and the thyroid drug levothyroxine (12.2%).
The most commonly used dietary supplements among survey participants were:
- multivitamins (28%)
- calcium (17%)
- vitamin C (9%)
- vitamin E (8.4%)
- B vitamins (7.7%)
- chondroitin-glucosamine (7.4%)
- potassium (6.8%)
- folic acid (5.2%)
- vitamin D (4.5%)
- omega-3 fatty acids (4.5%)
The blood thinner warfarin (also known as Coumadin) was used by just 4.4% of those surveyed, but it was identified as the prescription drug most likely to be associated with an adverse reaction, specifically bleeding.
The most widely reported potentially dangerous combinations were:
- warfarin and aspirin (increased risk for bleeding)
- warfarin and the statin drug Zocor (increased risk for bleeding)
- potassium and the blood pressure drug Prinivil (increased risk for high blood potassium levels)
- niacin and Lipitor (increased risk for muscular disorders)
None of the people surveyed was taking drug combinations that are absolutely forbidden. "That was the really good news here," Lindau says. "What it tells us is that our safety system seems to be working, at least for the most commonly used prescription drugs."
Experts: 'Keep a List of Drugs'
But it was still common for older people to be taking potentially dangerous, if not expressly forbidden, drug combinations. One big reason for this is that they often see specialists who may not ask about all the drugs they are taking.
"Patients need to be proactive by keeping a list of all their medications in their wallets and making sure that close family members also have the list," Lindau says.
Study co-author and pharmacist Dima Qato tells WebMD that it is also a good idea to use a single pharmacy or pharmacy chain so that all the drugs you take will be in one database.
Because little research has been done on interactions between prescription drugs and nutritional supplements, geriatrician Laurie Jacobs, MD, of New York's Albert Einstein College of Medicine and Montefiore Medical Center, says the interactions identified in the survey probably represent "the tip of the iceberg."
"The problem is even when patients tell their physicians about the supplements they are taking, the physician may not know what the potential for interaction is because those studies have not been done," she says.