Association of potentially inappropriate medication use with adverse outcomes in ambulatory elderly patients with chronic diseases: experience in a Taiwanese medical setting.

BACKGROUND: Potentially inappropriate medication use among the elderly in an outpatient setting has been widely reported. However, the potential association between inappropriate medication use and adverse outcomes is seldom examined.
OBJECTIVES: To identify the prevalence, risk factors for and adverse outcomes of potentially inappropriate medication use in ambulatory elderly patients with chronic diseases.
METHODS: Data for this observational cohort study consisted of computerized claims from a tertiary medical centre in Taiwan to the Bureau of National Health Insurance. Consecutive ambulatory elderly patients aged > or = 65 years who received long-term (3-month) prescriptions for treatment of a chronic disease were recruited from 1 to 31 March 2005. The cohort included 5741 elderly patients who received 7538 long-term prescriptions. Patients who required repeat prescriptions were able to be given the same prescription if their conditions were stable. The prevalence of potentially inappropriate medication use and the incidence of adverse outcomes, including emergency visits, hospitalizations and mortality, were documented for up to 6 months after the first day the patient was recruited. Beers' 2002 criteria were used to determine the potential inappropriateness of prescribed medications. Associations between potentially inappropriate medications and adverse outcomes were examined by multivariate logistic regression analyses controlling for possible confounding factors.
RESULTS: The prevalence of potentially inappropriate medication use was 23.7% in the studied hospital. The most frequently prescribed potentially inappropriate medications of high severity (i.e. having a high likelihood of being associated with an adverse effect that was clinically significant) were amiodarone, chlorzoxazone, bisacodyl, nifedipine and amitriptyline. Logistic regression analysis revealed that female sex, advanced age, number of chronic diseases and number of medications taken all significantly increased the likelihood of receiving potentially inappropriate medications. The incidence of adverse outcomes in patients with potentially inappropriate medication use in the studied hospital was 25.1%. Multivariate logistic regression analysis revealed that potentially inappropriate medication use was significantly associated with hospitalization.
CONCLUSIONS: Potentially inappropriate medication use is not a rare event in elderly patients and is associated with higher risk of hospitalization in this age group. In order to reduce the possibility of prescribing inappropriate medications, and therefore to reduce the consequent risk of hospitalization, more attention should be paid when prescribing drugs to, in particular, older female patients with multiple chronic illnesses that require treatment with multiple medications.