Risk of ischemic stroke during the initiation period of α-blocker therapy among older men.

Abstract

Alpha-blockers are notorious for their first-dose effect of acute hypotension during the early initiation period. Because acute cerebral hypoperfusion may precipitate an episode of ischemic stroke, we aimed to provide a quantitative estimate of the risk of ischemic stroke during the early initiation period of α-blocker therapy, using a self-controlled case series design. We identified all men aged 50 years or more as of 2007 who were incident users of α-blockers and had a diagnosis of ischemic stroke during the 2007-2009 study period using claims data from Taiwan's National Health Insurance claims database. The first day on which the α-blocker was prescribed was the index date. We partitioned different risk periods according to their relationship to the index date (pre-exposure risk periods 1 and 2 = ≤ 21 d and 22-60 d before index date, respectively; post-exposure risk periods 1 and 2 = ≤ 21 d and 22-60 d after index date, respectively); the remainder of the study period was defined as the unexposed period. We estimated the incidence rate ratio (IRR) of ischemic stroke in each risk period relative to the unexposed period using a conditional Poisson regression model. A total of 7502 men were included. Compared with the risk in the unexposed period, the risk of ischemic stroke was increased in post-exposure risk period 1 among all patients in the study population (adjusted IRR 1.40, 95% confidence interval [CI], 1.22-1.61) and among patients without concomitant prescriptions for other antihypertensive agents (adjusted IRR 2.11, 95% CI 1.73-2.57). Alpha-blocker therapy was associated with an increased risk of ischemic stroke during the early initiation period, especially among patients who were not taking other antihypertensive agents.