Prevalence of the Prescribing of Potentially Inappropriate Medications at Ambulatory Care Visits by Elderly Patients Covered by the Taiwanese National Health Insurance Program

Background: The use of potentially inappropriate medications can have profound medical consequences for elderly patients and place a substantial burden on the health care system. Objectives: This study was conducted to determine the prevalence of potentially inappropriate medication prescribing at ambulatory care visits by patients aged >= 65 years covered by the Taiwanese National Health Insurance program, to examine the characteristics of and risk factors for such prescribing, and to investigate its influence on health care resource utilization. Methods: Ambulatory care visits by patients aged >= 65 years in 2001-2004 were identified from the National Health Insurance claims database. The 2003 Beers criteria for drugs to be avoided in the elderly were used to identify potentially inappropriate medications prescribed at these visits. Only drugs with the potential to lead to higher-severity adverse events were included. Multivariate logistic regression was used to determine predictors of the prescribing of potentially inappropriate medications at ambulatory care visits. Independent variables in the regression model included patient characteristics (eg, sex, age), physician characteristics (sex, age, and specialty), and visit characteristics (site and prescribed drug number), The dependent variable was visits that included a prescription for a potentially inappropriate medication. Results: Overall, 176,661,994 ambulatory care visits by patients aged >= 65 years were identified in 2001-2004. Of these, 19.1% involved a prescription for a potentially inappropriate medication. Although the frequency of potentially inappropriate medication prescribing declined over the study period, 62.5% of elderly patients were exposed to such medications in 2004. The only patient characteristic associated with an increased likelihood of the prescribing of potentially inappropriate medications was female sex (male sex: odds ratio [OR] = 0.982 [95% CI, 0.980-0.983], P < 0.001). Physician characteristics associated with a greater likelihood of the prescribing of potentially inappropriate medications was male sex (OR = 1.206 [95% CI, 1.202-1.210], P < 0.001); older age (43-50 years: OR = 1.021 [95% CI, 1.018-1.025], P < 0.001; >= 51 years: OR = 1.238 [95% Cl, 1.235-1.242], P < 0.001); and family medicine/general practice (OR = 1.267 [95% Cl, 1.265-1.269], P < 0.001). For visit characteristics, significant associations were found with visits to a primary care clinic (OR = 1.887 [95% Cl, 1.881-1.892], P < 0.001) and the number of drugs prescribed (4-6 drugs: OR = 2.701 [95% Cl, 2.696-2.706], P < 0.001; >= 7 drugs: OR = 4.528 [95% CI, 4.517-4.538], P < 0.001). The most commonly prescribed types of potentially inappropriate medications were antihistamines (4.8% of all prescriptions in 48.3% of elderly patients), muscle relaxants/antispasmodics (4.0% and 40.3%, respectively), and long-acting benzodiazepines (2.4% and 21.4%). In 2004, the mean number of ambulatory care visits per patient was significantly higher among those who received potentially inappropriate medications compared with those who did not (30.78 vs 16.57, respectively; P < 0.001). Patients who received potentially inappropriate medications also had significantly more emergency department visits (0.27 vs 0.15; P < 0.001) and hospital admissions (0.46 vs 0.27; P < 0.001). Conclusion: There was a high prevalence of the prescribing of potentially inappropriate medications at ambulatory care visits by elderly patients in Taiwan in 2001-2004. (Clin Ther. 2009;31:1859-1870) (C) 2009 Excerpta Medica Inc.