Objective To systematically review and evaluate the effectiveness and adverse effects of the α‐antagonist, terazosin, for treating urinary symptoms associated with benign prostatic obstruction (BPO).

Methods Studies were sought and included in the review if they were randomized trials of at least 1 month duration, involved men with symptomatic BPO and compared terazosin with placebo or active controls. The study, patient characteristics and outcome data were extracted in duplicate onto standardized forms using a prospectively developed protocol.

Results Seventeen studies involving 5151 men met the inclusion criteria, i.e. placebo‐controlled (10), α‐blockers (seven), finasteride alone or combined with terazosin and placebo (one), and microwave therapy (one). The study duration was 4–52 weeks; the mean age of the men was 65 years and 82% were white. Baseline urological symptom scale scores and flow rates showed that men had moderate BPO. Efficacy outcomes were rarely reported in a way that allowed for data pooling, but indicated that terazosin improved symptom scores and flow rates more than did placebo or finasteride, and similarly to other α‐antagonists. The pooled mean percentage improvement for the Boyarsky symptom score was 37% for terazosin and 15% for placebo (four studies). The mean percentage improvement for the American Urological Association symptom score was 38%, compared with 17% and 20% for placebo and finasteride, respectively (two studies). The pooled mean improvement in the International Prostate Symptom Score of 40% was similar to that with tamsulosin (43%). Peak urinary flow rates improved more with terazosin (22%) than with placebo (11%) and finasteride (15%), but did not differ significantly from the other α‐antagonists. The percentage of men discontinuing terazosin was comparable with those receiving placebo and finasteride, but greater than with other α‐antagonists. Adverse effects were greater than with placebo and included dizziness, asthenia, headache and postural hypotension.

Conclusions The available evidence indicates that terazosin improves the symptoms and flow rates associated with BPO; it was more effective than placebo or finasteride and similar to other α‐antagonists. Adverse effects were generally mild but more frequent than with other α‐antagonists and associated with a two‐ to four‐fold increase in treatment discontinuation.