Alpha-blockers and urinary obstruction

This study evaluated the effects of alpha-blockers on urinary obstruction among men with benign prostatic hyperplasia (BPH). The authors concluded that alpha-blockers are effective at improving urinary flow and BPH-related urinary obstruction symptoms.

Alpha-blockers are often the first choice for treating BPH-related symptoms. The alpha-blockers commonly prescribed for BPH treatment include doxazosin (Cardura), tamsulosin (Flomax), terazosin (Hytrin), naftopidil (Flivas), alfuzosin (Uroxatral), and silodosin (Rapaflo). However, the effects of alpha-blockers on parameters of urine flow and urinary obstruction remain unclear. The focus of this review was to establish the specific effects of various alpha-blockers on urinary flow and obstructive symptoms.

Seventeen separate randomized trials, including a combined total of 656 men with BPH, were included in this review. Men received treatment with either doxazosin, tamsulosin, terazosin, naftopidil, alfuzosin, or silodosin. Bladder obstruction (blockage of the urinary tract due to the enlarged prostate), urine flow rate, and bladder pressure were compared between alpha-blocker treatment and placebo (a substance with no active effect used as a control). 

On average, bladder pressure during urination (an indicator of outlet obstruction) was reduced after treatment with alpha-blockers, when compared to placebo. This was associated with increased urine flow. Treatment with alpha-blockers was noted to significantly reduce the degree of bladder obstruction compared to placebo. The greatest reduction was observed with silodosin, followed by doxazosin. Similar reductions in bladder obstruction were noted for aftopidil, alfuzosin, and tamsulosin. Terazosin was associated with a more modest improvement, when compared to placebo. Improvements were particularly noted among men who showed a greater degree of bladder obstruction before treatment.

This large meta-analysis (an analysis of pooled data from several trials) concluded that alpha-blockers reduce bladder obstruction caused by enlarged prostates and facilitate urine flow. Men with greater degrees of bladder obstruction may particularly benefit from treatment with alpha-blockers.