MEDICATION USE IN THE OLDER POPULATION
This section begins by summarizing recent studies conducted in the United States describing the medication use of the community-dwelling older population. The majority of data in these studies were obtained through pharmacy claims databases, although in a few studies reported below, data were obtained through subject interviews, and to a lesser degree from biochemical sampling in trauma centers. Prescription medication use is described first, followed by over-the-counter (OTC) medication use, and the concurrent use of medication and alcohol. This section concludes with summaries of studies conducted on the prevalence of medication use in the community-dwelling older population of other countries. In light of changing practice and prescribing patterns over time, it should be kept in mind that the individual medications discussed may change over time but the underlying principles may apply to other drugs in the same categories.
In a recent and comprehensive national survey of U.S. noninstitutionalized adults, Gurwitz (2004) reported that more than 90 percent of people 65 or older use at least 1 medication per week; more than 40 percent of this population use 5 or more different medications per week; and 12 percent use 10 or more different medications per week.
In a cohort study of nearly 28,000 Medicare+Choice enrollees cared for by a multispecialty practice (an ambulatory clinic setting) during a 12-month study period during 1999 and 2000, researchers found that 75 percent of the sample received prescriptions for 6 or more prescription drugs (Gurwitz et al., 2003). Residents of long-term-care facilities were excluded from the study. The average age of the subjects in the sample was 74.7 (sd=6.7). The age and gender distribution of the sample was similar to that of the U.S. population 65 and older. Forty-nine percent of the sample was prescribed medications in four or more categories. Combinations of medication use were not reported; however, the specific prescription medication categories and percentage of enrollees receiving prescriptions were as follows:
The objective of the study by Gurwitz et al. (2003) was to document the incidence and preventability of adverse drug events. An adverse drug event (ADE) was defined in the study as “an injury resulting from the use of a drug.” To provide some background, adverse drug events include “expected adverse drug reactions (or side effects) as well as events due to errors” (Agency for Healthcare Research and Quality). Adverse drug events due to errors are, by definition, preventable. In contrast, an adverse drug reaction, according to the World Health Organization (1975) definition is “any response to a drug which is noxious and unintended, and which occurs at doses normally used in humans for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiological function.” It implies that there was no error in the use of the drug. Examples of an injury could include an event such as a rash or diarrhea caused by an antibiotic/anti-infective agent; gastrointestinal tract events such as nausea, vomiting, diarrhea, constipation and abdominal pain; anaphylaxis (a serious allergic reaction) to penicillin; a major hemorrhage from a blood-thinning agent; and kidney failure from aminoglycosides (antibiotics that are often administered into veins or muscle to treat serious bacterial infections).
In the Gurwitz et al. (2003) study, events were categorized as fatal, life-threatening, serious, or significant. Events resulting in permanent disability included stroke, intracranial bleeding events, hemorrhagic injury to the eye, and drug-induced pulmonary injury. Deaths in the study were related to fatal bleeding; peptic ulcers; neutropenia/infection; hypoglycemia; drug toxicity related to lithium or digoxin; anaphylaxis; and complications of antibiotic-associated diarrhea. There were 1,523 identified adverse drug events, of which 421 (27.6%) were considered preventable. Of the 578 serious, life-threatening, or fatal adverse drug events, 42 percent (244) were deemed preventable. Of the 945 significant adverse drug events, 19 percent (177) were deemed preventable. The most common types of preventable adverse drug events were: electrolyte/renal (27%), gastrointestinal tract (21%), hemorrhagic (16%), metabolic/endocrine (14%), and neuropsychiatric (9%). The most common medication categories associated with preventable adverse drug events are presented below:
Errors described in the study by Gurwitz et al. (2003) most often occurred at the stages of prescribing (246 events, or 58.4%) and monitoring (256 events, or 60.8%), although patient adherence errors were also common (89 events, or 21.1%). Gurwitz et al. (2003) note that if the findings of the study are generalized to the population of all Medicare enrollees, then more than 1,900,000 adverse drug events—more than a quarter of which are preventable—occur each year among 38 million Medicare enrollees. In addition, study estimates suggest that there are in excess of 180,000 life-threatening or fatal adverse drug events per year, of which more than 50 percent may be preventable.
The issue of polypharmacy in the elderly is confounded by the use of so-called “potentially inappropriate” medications. The identification of potentially inappropriate medication use has employed the Beers criteria (Fick et al., 2003); t he criteria consider “…(1) medications or medication classes that should generally be avoided in persons 65 years or older because they are either ineffective or they pose unnecessarily high risk for older persons and a safer alternative is available and (2) medications that should not be used in older persons known to have specific medical conditions.” The recent update of the Beers criteria found 48 individual drugs or classes of drugs to avoid in older adults and 20 diseases, conditions, and medications that should be avoided in the elderly with these conditions. The Zhan criteria extends the Beers list of drugs to identify drugs that should always be avoided, are rarely appropriate, or have indications for use in elderly patients but are frequently misused (Zhan et al., 2001) . Inappropriate medications complicate polypharmacy, because many of the drugs classified as potentially inappropriate are associated with adverse drug reactions (ADRs), some offer little or no advantage over other, safer drugs, and some have a long half-life in older patients.
Several studies of the incidence of potentially inappropriate medication use have been reported. These studies are summarized below, and reinforce the view that potentially inappropriate medication use is common in the elderly and that is a significant confounding issue when assessing the effect of combinations of medicines. Appendix A provides detail about the specific drugs, their classification, and side effects relevant to a discussion of safe driving ability.
Raji et al. (2003) used home interviews to examine the prevalence and predictors of inappropriate prescription medication use by 3,050 Mexican-Americans 65 and older living in the southwestern United States Approximately 12 percent of the sample had used at least 1 of the 32 potentially inappropriate medications within two weeks of the assessment. Four drugs accounted for 54 percent of all inappropriate prescribing: chlorpropamide,1 propoxyphene,2 amitriptyline,3 and dipyridamole.4
The following characteristics were predictive of the subjects who were prescribed at least 1 of the 32 drugs on the list of inappropriate medications: being unmarried, having 1 or more chronic diseases, having high depressive symptoms, having frequent physician visits, and having both Medicaid and Medicare insurance (Raji et al., 2003). The odds of using any inappropriate drugs were 2.4 times greater in subjects reporting 2 or more medical conditions compared with those reporting no medical conditions. The odds of using any inappropriate drugs were approximately 6 times greater in subjects reporting 2 or more physician visits, compared with those reporting no visits. Subjects with 1 or 2 visits had 4.3 times the risk of receiving at least 1 of the 32 potentially inappropriate drugs relative to those reporting no visits.
Kamal-Bahl et al. (2003) used the data from the 1998 Medicare Current Beneficiary Survey (MCBS) to provide a national prevalence estimate of the number of community dwelling Medicare beneficiaries 65 and older who are prescribed propoxyphene. In addition to the opioid-related adverse effects associated with this medication (e.g., drowsiness, dizziness, lightheadedness), several studies were cited by Kamal-Bahl et al. (2003) that have demonstrated that it is no more effective than acetaminophen, aspirin, codeine, or ibuprofen in reducing pain and may even be inferior. This medication is listed on the Beer’s list of potentially inappropriate drugs for elderly people (Beers, 1997) and is classified by the Zhan expert panel as a drug that is “rarely appropriate” (Zhan et al., 2001). The MCBS database includes statistical weights for each respondent that can be used to generate nationally representative estimates from the survey sample. The study sample consisted of all MCBS respondents 65 or older who were community-dwelling (n=9,851, weighted n = 32.5 million) during 1998. The annual prevalence of propoxyphene use was 6.8 percent. Approximately 69 percent of the propoxyphene prescriptions in the community were combination products with another analgesic, namely acetaminophen.
Aparasu and Mort (2004) examined data from the 1996 Medical Expenditure Panel Survey (MEPS) to analyze the use of psychotropic medications that generally should be avoided in the elderly and those that should be avoided in elderly patients with certain preexisting conditions, as defined by the Beers criteria. The MEPS sampling weights were used to derive national estimates. It was estimated that nationally, 6.09 million older patients (19% of 32.29 million older patients) use psychotropic medications; 64 percent are female. Further, it was estimated that 2.3 million community-dwelling older people received potentially inappropriate psychotropic medications in 1996, which represents 7.14 percent of all community-dwelling older people and 37.86 percent of all community-dwelling older people using psychotropic agents. Thirty-three percent of those taking psychotropic drugs received agents that were generally inappropriate and 10 percent received agents that were inappropriate in the presence of specific conditions. The rate of potentially inappropriate psychotropic use in those receiving antidepressants was 51 percent, for antianxiety agents was 32 percent, and for sedative/hypnotic agents was 23 percent.
The most frequently used potentially inappropriate antidepressants are amitriptyline5 and doxepin.6 These agents are to be avoided in the elderly because of their anticholinergic7 and sedative effects. Use of diazepam,8 a long half-life benzodiazepine alone (56.89%) and use of a sedative in patients with chronic obstructive pulmonary disease (COPD, 62.65%) constituted more than half of the potentially inappropriate antianxiety and sedative/hypnotic use, respectively. Age less than 75 and use of multiple psychotropic agents were correlated with the use of potentially inappropriate psychotropic agents. For older people taking antidepressants, the use of potentially inappropriate antidepressant agents was significantly higher (4 times) among those younger than 70 compared to those 85 and older. For those taking sedative/hypnotic agents, age between 70 and 79, and having only Medicare coverage were positively associated with the use of potentially inappropriate sedative/hypnotic agents. However, older patients with Medicaid coverage were significantly less likely to use potentially inappropriate sedative/hypnotic agents than those without Medicaid coverage.
A table follows on the next page containing a summary of the studies discussed above and others bearing on the use of drugs on the Beers list by community-dwelling populations in the United States.
1 Chlorpropamide (“Diabinese”) is used to treat type II (noninsulin-dependent) diabetes. It lowers blood sugar by stimulating the pancreas to secrete insulin and helping the body to use insulin efficiently.
2 Propoxyphene (“Darvon Puvules,” “Darvon-N”) is used to relieve mild to moderate pain. It should not be taken in combination with other drugs that cause drowsiness: alcohol, tranquilizers, sleep aids, antidepressant drugs, or antihistamines.
3 Amitriptyline (“Elavil”; “Endep”; “Limbitrol” [combination with chlordiazepoxide]) is used to treat symptoms of depression. Amitriptyline is in a class of medications called tricyclic antidepressants.
7 Anticholinergic agents diminish the effect of acetylcholine, a neurotransmitter that in many ways counteracts the effect of dopamine in the brain. Adverse anticholinergic effects include decreased cognition, sedation, blurry vision, confusion, and instability.