WEDNESDAY, Dec. 17 , 2003 (HealthDayNews) -- Two drugs are better than one when it comes to treating men with enlarged prostates.
Doxazosin and finasteride worked in concert to reduce severe complications from the condition and the need for surgery, claims an article in the Dec. 18 issue of the New England Journal of Medicine.
"This is a nice add-on, but [the combination therapy] has certain intricacies that all must be looked at," says Dr. Perinchery Narayan, director of the North Florida Research Institute in Gainesville.
Enlargement of the prostate affects more than half of American men over the age of 50. The prostate is located next to the urethra, which passes urine from the body, and the bladder. When enlarged, it can pinch the urethra and disrupt the flow of urine. In extreme cases, it can even cause "acute urinary retention," or the inability to urinate.
Doctors routinely prescribe one of two drugs for the condition: doxazosin, an alpha blocker, and finasteride, which is also used to treat baldness. More serious complications such as acute urinary retention may require surgery.
"Both these drugs have been used separately and individually for 10 years or more, in some cases with good success, but indiscriminately," says study co-author Dr. Claus G. Roehrborn, chairman of the department of urology at the University of Texas Southwestern Medical Center in Dallas. "Doctors didn't make a huge difference whether choosing one or the other."
Because the two drugs work by such different mechanisms, however, a combination approach "intuitively made sense," Roehrborn adds. Doxazosin essentially relaxes the muscle at the opening of the bladder so urine can flow.
"Alpha blockers give symptom relief but don't change the natural progression of the condition," explains Dr. Jed Kaminetsky, a clinical assistant professor of urology at New York University School of Medicine.
The other class of drugs, called 5 alpha-reductase inhibitors, works by a hormonal mechanism to shrink the prostate and ease the pressure on the urethra and bladder.
"These work very differently, so it should have made sense to use them in combination to have a synergistic effect," Kaminetsky says.
Two previous studies looked at the combination but failed to show a benefit, probably because they did not last long enough. A previous study, for which Narayan was an investigator, only followed patients on the combination therapy for one year. "Since [enlarged prostate] is a long-term disease that is progressive and occurs over many years, one year may be too short a period of time," Narayan notes.
The current study followed more than 3,000 men for about five years and is the largest study of its kind ever conducted.
Participants randomly received either doxazosin alone, finasteride alone, a combination of the two or a placebo.
Doxazosin reduced the risk of overall progression of the condition by 39 percent and finasteride by 34 percent. The combination therapy reduced this risk by 66 percent.
Finasteride and the combination therapy reduced the risk of acute urinary retention and the need for surgery. Doxazosin, by contrast, did not have an effect in these areas.
About 10 percent of the men taking finasteride experienced side effects in sexual function. Doxazosin users sometimes experienced dizziness, low blood pressure and fatigue.
Regardless of the positive results, treatment is not likely to led to a straightforward switch to combination therapy.
For one thing, a trial earlier this year found that while finasteride reduced the risk of some types of prostate cancer, it also increased the risk of other cancers. "Nobody expected these kinds of results with the prostate cancer prevention trial," Narayan says. "This complicates the picture."
Roehrborn thinks men at high-risk for progression could be started on both drugs at once, while low-risk patients could take one or the other.
A person's risk is determined by looking at prostate volume and PSA (prostate-specific antigen) level.
Also, an enlarged prostate is a complicated condition. Sometimes a prostate large in size is less troublesome than a smaller one. For this reason, finasteride wouldn't make any sense for a man with a small prostate, Kaminetsky says.
More information
For more on enlarged prostates, visit the American Academy of Family Physicians or the National Institutes of Health.
