Drug Therapy in the Elderly:
Drug Therapy in the Elderly:
There are currently about 35 million persons in this country over age 65-about 13% to 14% of the population. By 2020, it is projected that 1 in every 5 persons will be over age 65.1 The "oldest old"-those over age 85-constitute the most rapidly growing subsegment of this population; their numbers are expected to triple during the next 30 years.
In view of these estimates, it is not surprising that the management of medications in the elderly population is an area of considerable clinical importance. For example, of all deaths caused by adverse reactions to medications in 1986, 51% occurred in persons over age 60.2 In addition, 39% of all persons hospitalized because of an adverse reaction to medications were over age 60.2 Up to 100,000 patients die each year in US hospitals because of medical errors, and half of these deaths are medication-related.3
The toll of medication errors is considerable-not only in terms of morbidity and mortality but also in costs to the health care system. Data from the 1990s show that the rate of hospitalization for medication-related problems is 3 times higher in older persons.4 Medication errors account for an estimated 12% to 16% of all hospitalizations among persons over age 65.4 The estimated cost to the health care system of inappropriate drugs and the consequences of their use approaches $200 billion per year, half of which is incurred by the elderly.5,6
Here we discuss the factors that contribute to what former Secretary of Health and Human Services Lewis Sullivan termed "America's other drug problem." We review some of the challenges of prescribing for elderly patients-and offer recommendations for avoiding or minimizing adverse drug reactions.
POLYPHARMACY AND INAPPROPRIATE MEDICATIONS
Persons older than 65 years use 31% of all prescription drugs and purchase more than 40% of the over-the-counter (OTC) drugs sold in the United States.5,6 Studies of elderly persons who live independently show that they take an average of 6 different medications per day; those living in a long-term-care facility take an average of 8 medications.7,8 Polypharmacy heightens the risk of significant drug-drug interactions and other adverse events, particularly in frail elderly persons.
The use of medications that are inappropriate for older persons also increases the risk of adverse reactions. Beers and colleagues9,10 developed criteria for categorizing medications according to their risk in the elderly. An estimated 20% to 25% of elderly persons take at least 1 drug considered inappropriate based on the Beers criteria.11
Compliance, or adherence to a drug regimen, becomes problematic for elderly persons when the number of medications or the frequency of administration increases. However, the primary reason that older patients do not adhere to a regimen is the escalating cost of drugs. The cost of prescription drugs has increased more than two and a half times since 1993. A study found that 18% of older Californians either did not fill a prescription or skipped doses because of the high cost of medications; this percentage increased to 29% among those with no prescription drug coverage.12
AGE-RELATED PHARMACOKINETIC CHANGES
Increasing age can significantly affect drug absorption, distribution, metabolism, and elimination. Other factors-including frailty and comorbid conditions, such as congestive heart failure (CHF)-also affect drug kinetics in older persons.
The kinetic changes that affect younger elderly persons are likely to continue as a patient ages and to become more clinically relevant. A relatively new concept is the impact of frailty on kinetics: as a patient becomes more frail, the kinetic changes associated with aging become more significant.
A summary of the kinetic changes associated with age and disease is provided in Table 1. However, bear in mind that the heterogeneity of the aging population makes generalizations about kinetic changes in older persons problematic. In addition, current knowledge concerning aging and pharmacokinetic changes has largely been derived from data in patients between the ages of 65 and 74 years. There are far fewer data for those between 75 and 85 years and little or none for those older than 85 years.