Two workhorse drugs can be combined to strike a doubly powerful blow against symptoms of an enlarged prostate, an irritating and occasionally dangerous condition widespread in older men, a study found. Researchers say up to 7 million men might benefit from the combined drugs, which act in different ways on the body to ease such symptoms as weak or urgent urination.
"I can't think of many combination therapies where two drugs work by different mechanisms and jointly work so much better. It's a beautiful outcome,'' said one of the study's leaders, Dr. Claus Roehrborn, a urologist at University of Texas Southwestern Medical Center in Dallas.
The study was published Thursday in The New England Journal of Medicine. The five-year experiment with 3,047 patients at 17 hospitals coast to coast was the most ambitious study yet of drug treatments for enlarged prostate. It was backed by the National Institutes of Health.
The two drugs in the study, doxazosin and finasteride, are now widely used, but not normally combined, to treat an enlarged prostate. The study was designed to decide if they can be teamed up for a stronger effect. Often, such a drug combination fails to greatly boost effectiveness. This time, though, it succeeded.
On its own, each drug reduced the risk of worsening symptoms by about a third. Together, they worked twice as well, cutting the risk by two-thirds.
Over five years, the condition worsened in about 10 percent of patients on only one drug, but in only 5 percent of those who took the combination. Without either drug, the condition deteriorated in 17 percent.
"Although we had predicted that combination therapy would be more effective than either drug alone, the magnitude of risk reduction was surprising,'' said chief researcher Dr. John McConnell, also at Southwestern Medical Center.
Doxazosin relaxes muscles that tend to choke off the flow of urine. It is usually the first drug given for an enlarged prostate. Finasteride, which also goes by the brand name Proscar, slowly shrinks the prostate gland itself. It is contained in smaller amounts in the baldness drug Propecia.
The two-drug combination can cost about $3 a day. Half of men ages 51 to 60 and up to 90 percent of those over 80 have enlarged prostates, according to the American Urological Association.
The prostate, a semen-secreting gland, lies under the bladder. In middle age, it is about the size and shape of a chestnut. Over a man's lifetime, it might typically double in size, and can sometimes grow tenfold to the size of a baseball.
An enlarged prostate - medically known as benign prostatic hyperplasia - tends to squeeze off the flow of urine from the bladder, making it more difficult to urinate or causing an urgent need to urinate. Much more rarely, the flow is totally blocked, requiring quick surgery.
In the University of Texas study, finasteride alone and combination therapy worked equally well at warding off complete blockages. Doxazosin was not effective against this complication. The combination therapy worked better than either drug alone at controlling minor but annoying symptoms.
The frequency of known side effects from the drugs, including impotence and dizziness, remained small for dual therapy. However, the combination did appear to boost slightly the risk of abnormal ejaculation, ankle swelling and breathing trouble.
Also, earlier cancer research suggested finasteride reduces the overall likelihood of prostate tumors but may increase the risk of more aggressive ones.
The researchers said their findings show that combination therapy is the best all-purpose choice for many men. Roehrborn said around 40 percent of patients with this condition - about 3 million men - can now be considered for combination therapy.
Dr. E. Darracott Vaughan, a urologist at Cornell University's Weill Medical College, said up to 7 million men might theoretically benefit. Researchers said other members of the same two drug classes are apt to work similarly in tandem.