All six of the alpha blockers commonly used today in the United States have been demonstrated to be beneficial in the treatment of prostatic obstruction; however, both Phenoxybenzamine (Dibenzyline) and Prazosin (Minipress) are not commonly used anymore because to be effective they have to be taken more than once per day.
Terazosin (Hytrin) was studied in a randomized, placebo-controlled fashion and was found to be very effective in treating the symptoms of BPH. Two hundred eighty-five patients were entered into a study where placebo, or different doses of terazosin were given. Response rates were evaluated using subjective measures (symptoms were improved) and objective measures (urinary flow rate).
The percentages of patients exhibiting a greater than 30% improvement in symptom scores and flow rates appear in Figure “Symptom scores and flow rates” [Source: Kirby R, McConnell JD, Fitzpatrick JM, Roehrborn CG, Boyle P, eds. Textbook of Benign Prostatic Hyperplasia. Oxford, England: Isis Medical Media; 1996].
Doxazosin (Cardura) has also been proven to be efficacious in the treatment of BPH. Five double-blind, placebo-controlled clinical studies of doxazosin have been published in the literature. These studies demonstrated that doxazosin improved objective measurements such as flow rates, as well as subjective measurements such as symptom scores.
Tamsulosin (Flomax) is a more selective alpha blocker than either terazosin or doxazosin. It therefore has a lower systemic side-effect profile than terazosin or doxazosin. Like other alpha blockers, tamsulosin has a low incidence of dizziness (5.7%), hypotension (0.4%), or fainting (0.2%).
Alpha blocker drugs have been proven effective in treating the symptoms that are often associated with an enlarged prostate. Whenever you gauge the effectiveness of any therapy for the treatment of prostate symptoms, it is important to have a control group, as there is often a significant placebo effect observed in the treatment of prostatism. It is important to recognize that symptom score improvement is a subjective measure based on the patient’s perception as to whether his symptoms have improved after taking a drug. The peak flow rate is an objective measure based on the force of the patient’s urinary stream measured by a machine. Alpha blockers have been shown to be efficacious in the treatment of obstructive prostate disease by both objective and subjective measures. To date, no study has yet shown that alpha blockers reduce the risk of going into urinary retention.
Selections from the book: Kevin R. Loughlin, MD, MBA and John Nimmo, BA, MA, “100 Questions and Answers about Prostate Disease”, 2006.