Men with enlarged prostates should be given a cocktail of drugs as part of their treatment, a study suggests.
Patients fared best on both drugs
One in three men over the age of 50 suffer from benign prostatic hyperplasia - a non-cancerous condition
that causes them to urinate frequently.
Many receive one of two drugs to help treat the condition, namely finasteride or doxazosin.
But a five-year study involving more than 3,000 men in the US suggests they would fare better if they took both.
Doctors at 17 clinics across the United States were involved in the study - the Medical Therapy of Prostatic Symptoms (MTOPS) Trial.
The men involved in the study were given either finasteride or doxazosin, both drugs or a dummy pill.
Researchers found that men who received both drugs were 66% less likely to see their condition worsen compared with those taking the dummy pill.
They were less likely to need surgery and reported the greatest relief from symptoms.
In addition, they were less likely to report side effects compared with those on the other treatments.
The researchers said the combination therapy was most effective in men with particularly enlarged prostates.
Dr John McConnell, professor of urology at the University of Texas Southwestern Medical Center in Dallas who led the study, said patients clearly benefited from taking both drugs.
"The combination therapy offers dramatically greater and longer-lasting relief from symptoms and, over time, the finasteride shrinks the prostate and actually prevents growth so that fewer men at highest risk for progressive disease need surgery," he said.
Dr Claus Roehrborn, who was also involved in the trial, said: "A 66% reduction in the risk of anything in medicine is pretty substantial.
"This is good news. The fly in the ointment is that two tablets cost more than one, so there is a cost factor."
Professor Roger Kirby, of the British Association of Urological Surgeons, welcomed the study.
"At the moment, doctors generally use only one of these drugs," he told BBC News Online.
"This study shows for the first time that using these drugs in combination not only improves the symptoms but also prevents disease progression.
"It is quite a new finding and is something that can definitely be taken on board by doctors here in the UK."
The study is published in the New England Journal of Medicine.