Despite being a “selective” alpha blocker, tamsulosin (Flomax) carries a significant risk of severe hypotension in middle-aged and older men being treated for benign prostatic hyperplasia (BPH), according to a new study. Data were reviewed from the IMS Lifelink database of the records of nearly 400,000 new users of either tamsulosin or a 5-alpha reductase inhibitor (finasteride [Proscar] or dutasteride [Avodart]) used as comparators. Severe hypotension requiring admission to the hospital was higher with tamsulosin (42.4 events/10,000 person years) vs 5ARIs (31.3/10,000 person years). The rate was much higher within the first 8 weeks of initiation of tamsulosin or for 8 weeks if the drug was stopped and then restarted. The authors suggest that patients should be warned about the alpha blocker “first-dose phenomenon” with tamsulosin. The authors also point out that the selective alpha blockers doxazosin, prazosin, and terazosin all have black box warnings regarding severe hypotension and syncope whereas tamsulosin only has a standard warning regarding hypotension (BMJ 2013;347:f6320).