Prazosin (the prototype quinazoline alpha-1 blocker) was a short-acting agent that required multiple daily dosing (unless administered as a modified release formulation), whereas the newer longer-acting quinazoline derivatives (including doxazosin and terazosin) have been licensed for once-daily administration for the treatment of hypertension ( Box 82-1). Elliott, in Comprehensive Hypertension, 2007 Selective alpha-1 adrenoreceptor antagonists Treatment requires 6 mo or more for maximal effect. Both are 5 α-reductase inhibitors that block conversion of testosterone to dihydrotestosterone they can reduce the size of the prostate. Hormonal manipulation with finasteride (Proscar) 5 mg qd or dutasteride (Avodart) 0.5 mg qd. α-1 blockers are the most effective medical pharmacologic therapy for BPH-associated lower urinary tract symptoms. Prazosin, doxazosin, and terazosin are nonspecific α-1 blockers and are used to treat hypertension they can cause (postural) hypotension. Tamsulosin and alfuzosin are more specific to bladder α-1 receptors and do not cause much hypotension. α-1 blockers are useful in symptomatic patients to relieve symptoms of obstruction by causing relaxation of smooth muscle tone in the prostatic capsule and urethra and bladder neck. They have no effect on the size of the prostate. Α-1 blockers (e.g., tamsulosin, alfuzosin, doxazosin, prazosin, and terazosin) relax smooth muscle of the bladder neck and prostate and can increase urinary flow rate.
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