FACTORS AFFECTING COMPLIANCE WITH MEDICATION REGIMES
Researchers examining the medical records of approximately 28,000 Medicare enrollees 65 and older found that 89 of the 421 preventable adverse drug events (21%) were caused by “errors in patient adherence”—for example people taking the wrong dose, continuing to take medication despite instructions by the physician to discontinue drug therapy, refusal to take a needed medication, continuing to take a medication despite recognized adverse effects or drug interactions known to the patient, and taking another person’s medication (Gurwitz et al., 2003).
Barat, Andreasen, and Damsgaard (2001) found that 71 percent of their sample of subjects 75 and older showed dose deviations, most commonly lower-than-prescribed dosing and less frequent drug intake. The drugs most often involved in deviations were hypnotics, analgesics, bronchodilators, and diuretics. Fourteen percent of all participants receiving low-dose aspirin, 12 percent receiving diuretics, 13 percent using nitrates, 14 percent receiving calcium antagonists, and 12 percent receiving nonsteroidal anti-inflammatory drugs exceeded the prescribed dose. Fifty-eight percent of all subjects receiving hypnotics, 54 percent using nonsteroidal anti-inflammatory drugs, and 46 percent receiving analgesics used lower doses than prescribed.
Vik, Maxwell, and Hogan (2004) performed a review of the literature (1966 to 2002) on medication compliance among community-dwelling older adults and concluded that there are few empirical data to support a simple systematic descriptor of the nonadherent patient. The evidence emerging from their review suggests that polypharmacy and poor patient-health-care-provider relationships (including the use of multiple providers) are the major determinants of nonadherence, and that the impact of sociodemographic factors is negligible. Vik et al. (2004) report that the proportion of hospitalizations among older patients attributable to nonadherence may be as high as 11 percent.
The American Pharmacists Association (APhA, 2003), in its overview of compliance research and interventions, indicates that the five most common types of noncompliance are:
The APhA lists three groups of factors that may contribute to poor compliance: medication-related factors, patient-related factors, and prescriber-related factors. Recent findings reported in the literature in each of three areas are presented below.