本研究以全民健保1997~2002六年的門診申報檔案為範圍，分析新近降血壓藥品第二型血管張力素拮抗劑(Angiotensin Ⅱ antagonist, AIIA)進入市場後對原有降血壓藥品使用型態的影響。本研究分析有關藥品使用型態的參數包括：以定義日劑量(Defined Daily Dose, DDD)?單位之耗用量，處方數，臨床市場佔率(Clinical market share, CMS)，處方市場佔率(Prescription market share, PMS)及每次處方量。在AIIA進入台灣市場後，耗用量與處方數的成長率以鈣離子阻斷劑(Calcium channel blocker, CCB)?最高。Clinical market share與prescription market share的變異在AIIA及CCB?正成長，而其他類別的降血壓藥物則均?負成長。此外，由線性迴歸顯示AIIA的clinical market share與prescription market share在四個層級之增加率均?醫學中心＞區域醫院＞地區醫院＞基層醫療。本研究結果顯示AIIA及CCB在降血壓藥物的使用上呈現持續成長的趨勢，並且醫學中心對AIIA的利用與擴散具有關鍵性之角色。

This study aimed to evaluate the long term impact of a new pharmacological class antihypertensive medicine-angiotensin Ⅱ antagonist (AIIA) on the clinical utilization of existing antihypertensive medications in Taiwan. Claims data of medical service and prescriptions of antihypertensive agents during 1997 to 2002 were obtained from National Health Insurance Research Database (NHIRD). Gross growth of defined daily dose (DDD) and prescription numbers, clinical market share and prescription market share analysis, market penetration time and DDDs/prescription were used to assess AIIA's impact on the angiotensin converting enzyme inhibitors (ACEI), ?-Blockers, calcium channel blockers (CCB) and other miscellaneous antihypertensive agents. CCB had the highest gross growth of DDDs and prescription at 117.1 and 3.4 million increments, respectively. Analysis of clinical market share revealed that the introduction of AIIA had the most significant impact to the clinical utilization of miscellaneous antihypertensive agents (-5.5%) and a moderate impact on both ?-blockers (-4.5%) and ACEI (-4.1%). Whereas the greatest impact of prescription market share was observed with miscellaneous antihypertensive agents (-6.5%), a moderate impact with ACEI (-2.3%) and a very minor impact with ?-blockers (-0.9%). CCB, however, had a positive clinical market share (+3.9%) and prescription market share (+2.4%) correlated with AIIA. AIIA utilization implicated by relative growth strength for the clinical market share and prescription market share at medical center, regional hospital, district hospital and primary care clinic were 4.95:3.77:2.77:1 and 5.28:4.17:2.94:1, respectively. The introduction of AIIA did not affect the decreasing trend of clinical utilization of miscellaneous antihypertensive agents and ?-blockers since this downtrend started before AIIA introduction. On the other hand, there was increasing usage of CCB and AIIA to control hypertension in Taiwan. Medical centers were the early adaptors for AIIA and played an important role in the utilization diffusion of AIIA.