Impact of introduction of angiotensin II antagonist on the antihypertensive utilization in Taiwan

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), β-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 B-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 β-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 β-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.