Background: Treatment of benign prostatic hyperplasia (BPH) with nonselective alpha1 antagonists such as terazosin, doxazosin, and prazosin results in blood pressure reduction due to vasodilation.
Objective: Using claims data from a large Medigap plan, we examined the effect of initiating nonselective alpha1-antagonist therapy on the incidence of hypotension-related adverse events likely to be associated with vascular alpha-adrenoreceptor antagonism in patients with BPH.
Methods: Medical and prescription claims data were obtained from the MEDSTAT Group for 53,824 men with a diagnosis code for BPH during the study period (January 1995-December 1997). We examined the rate of possible hypotension-related adverse events (diagnosis codes for hypotension, syncope, dizziness, fractures, and other injuries) per 10,000 person-days for men who began therapy with alpha1 antagonists and for a random sample of nonusers, stratified by prior use of other antihypertensive agents.
Results: After adjusting for baseline differences in event rates, those who initiated alpha1-antagonist therapy (n = 1564) had a significantly greater increase in hypotension-related adverse-event rates in the 4 months after initiation (vs the 4 months before initiation) than randomly selected nonusers (n = 8641) (increase of 1.82 vs decrease of 0.02 events per 10,000 person-days among those not taking antihypertensive agents; increase of 0.94 vs 0.69 events per 10,000 person-days among those taking other antihypertensive agents; P < 0.01). This increase began earlier and lasted longer among patients taking other antihypertensive agents. Those who discontinued their alpha1 antagonist had a higher rate of hypotensive events at baseline than those who did not (5.09 vs 3.19 events per 10,000 person-days among those using other antihypertensive agents; 3.62 vs 2.27 events per 10,000 person-days among those not using other antihypertensive agents; P < 0.05).
Conclusions: Initiation of nonselective alpha1-antagonist therapy for the treatment of BPH increases the risk of a cluster of clinical events consistent with vascular alpha-adrenoreceptor antagonism. This effect is seen during a 4-month period around the initiation date. Prior initiation of other antihypertensive medication increases this effect. Urologists should consult with a patient's primary care physician about use of other antihypertensive agents before initiating nonselective alpha1-antagonist therapy for BPH.