Alpha-blockers are not first-line agents for many conditions, but they are often tested on exams and highly relevant in practice—especially in urology, hypertension, and acute care settings. Understanding their nuances can help prevent serious adverse effects and optimize patient outcomes. Here are my top 5 testable pearls on alpha-blockers.

Selectivity

Not all alpha-blockers are created equal. Some alpha-blockers tend to affect the vasculature more than others. doxazosin, prazosin, and terazosin will have a greater effect on the vessels compared to tamsulosin, alfuzosin, and silodosin. When treating BPH symptoms like urinary retention, we tend to avoid the agents that have more effects on vessels to avoid hypotension.

First Dose Hypotension

One of the most testable and clinically relevant adverse effects of alpha-blockers is first-dose syncope. This is most pronounced with doxazosin and terazosin, particularly when started at higher doses or in volume-depleted patients. It is also very important to be cautious with these agents in geriatric patients who may be more at risk for falls and dizziness.

BPH Symptom Relief – Fast Onset

Alpha-blockers improve urinary flow and reduce lower urinary tract symptoms by relaxing smooth muscle in the prostate and bladder neck. However, they do not shrink the prostate or reduce PSA. This mechanism leads to a much quicker improvement in symptoms compared to the 5-alpha-reductase inhibitors, which take a long time to shrink the prostate.

Floppy Iris Syndrome

Intraoperative floppy iris syndrome is associated with tamsulosin, even if the drug was stopped months earlier. If there is a planned eye procedure, it is very important to notify an eye doctor that you (or your patient) are taking an alpha-blocker.

Prazosin For Nightmares

Uniquely, you may see prazosin prescribed by psychiatrists for reducing nightmares. By blocking alpha-1 receptors in the brain, prazosin dampens norepinephrine signaling. This reduces nighttime hyperarousal, decreases REM-associated sympathetic activation, and leads to fewer and less intense nightmares. Importantly, prazosin does not suppress REM sleep itself; instead, it improves the quality and stability of sleep by lowering adrenergic overactivity.

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