Objectives: To analyze inappropriate prescriptions at the market and hospital levels by examining antihypertensive medication ordering quality in out-patient departments (OPD) in Taiwan hospitals. Methods: Our sample included 398 accredited acute hospitals located in 23 regions. Information about hospital's ownership, rank, teaching status, OPD visits and hospital number published by the Department of Health (DOH) and information from the 2009-2011 Quality Database of Medications Indicators published by National Health Insurance were collected. The population density (PD) and physician density per 10000 population (PDPP) in the 23 regions were generated from DOH data. Two inappropriate prescription indicators were defined as duplicate medications of oral blood pressure-lowering agents or hypertension patients with a history of hyperkalemia using PSD or AA. We used MLLR models to assess multilevel effects on the probability of good or bad hospital quality for medications. The market concentration in the 23 regions was calculated by Herfindahl-Hirschman Index (H) using OPD visits to measure hospital competition. Results: Our study showed that higher H and PD led to greater probability of low duplicate medications. A higher PDPP led to lower probability of low duplicate medications. When compared to hospitals located in the Eastern region, the probability of low duplicate medications in Taipei, Southern, Kaohsiung-Pingtung areas is lower. The probability of low duplicate medications in teaching hospitals is lower than non-teaching hospitals and medical centers are higher than local hospitals. The probability of appropriately treating patients with hyperkalemia in Taipei, Northern, Southern, and Kaohsiung-Pingtung areas was higher than that of Eastern areas. Overall, the variation of medication quality can be explained 10.25%-17.63% by hospital-level variables and 73.40%-82.52% by market-level variables. Conclusions: Hospital and market characteristics impacted inappropriate prescriptions of anti-hypertensive drugs in the OPD setting over the past 3 years.

降血壓藥物；處方品質；醫院；門診；多層次邏吉斯迴歸

anti-hypertension agents; prescriptions quality; hospital; outpatient; multi-level logistic regression