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General Principles in Older Adults
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Older adults are the largest consumers of prescription drugs. A large survey reported that more than one-half of patients 57–85 years old used at least 5 prescription medications, nonprescription medications, and nutritional supplements. Predictably, the number of medications steadily increased with the age of the patient. This survey also reported that 1 in 20 of these patients risked a major drug–drug interaction; half of these interactions included a nonprescription agent. Research demonstrates that polypharmacy is an independent risk factor for adverse outcomes, including hospitalization, nursing home placement, hypoglycemia, falls and fractures, pneumonia, and malnutrition, and death. Older adults are also generally less tolerant to the effects of a medication. This intolerance can manifest as an exaggerated effect of a medication or even a different effect as compared to younger patients, and is described at length in Chapter 9, “Principles of Prescribing for Older Adults.”
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Problems Caused by Polypharmacy
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Table 53–1 lists several major problems caused by polypharmacy. The primary purpose of a medication also may be the source of an adverse drug reaction (ADR). A national study of emergency room patients showed that anticoagulants (including both warfarin and antiplatelet drugs) and diabetes drugs (including both insulin and oral medications) were responsible for two-thirds of all medication-related hospitalizations. In contrast, medications considered “inappropriate” by the Beer’s criteria accounted for only 7% of hospital admissions. Of these admissions, more than one-half were caused by digoxin alone.
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Polypharmacy raises the risk of drug–drug and drug–disease interactions, particularly in older adults. The causes and consequences of such interactions are discussed in Chapter 9. In addition to known interactions, it is likely that clinically important interactions are yet to be discovered. Therefore, physicians should eliminate all unnecessary drugs, regardless of whether they are currently causing an obvious problem.
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Similarly, polypharmacy increases the likelihood that patients will not adhere to their medication regimen. Nonadherence to medications contributed to 20% of the ADRs in an ambulatory setting. A number of factors may contribute to nonadherence.
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Practice guidelines, for example, are primarily written by specialists for the management of a single condition. Physicians must then combine guidelines in an older patient with multiple conditions. For a hypothetical patient with chronic obstructive pulmonary disease, type 2 diabetes, osteoporosis, hypertension, and osteoarthritis, guidelines require 12 medications with multiple daily dosing regimens. Moreover, prescribing a drug may be easier than more time-consuming interventions such as lifestyle modification or nonpharmacologic treatments. Yet, patients may be less likely to adhere to medications as the regimen grows increasingly complex.
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For both patients and the health care system, cost is also ...