Proscar is an important new drug used to treat symptoms of enlarged prostate glands, but along with this benefit it also has side effects that remain to be assessed.
The drug, manufactured by Merck & Co. of Rahway, N.J., was approved for marketing June 19 by the Food and Drug Administration. It is safe and offers many older men the prospect of avoiding surgery, experts and company officials said at a news conference June 22.
A daily Proscar pill can shrink an enlarged prostate gland, studies have shown. But patients may need to be treated for at least six months to determine whether they will respond to the drug, and there is no way to predict which patients will benefit from the drug.
Proscar must be taken for a lifetime and will cost a patient about $640 a year.
The drug's generic name is finasteride, and Merck said it would be available for prescription use in late July. Proscar is the first of a new class of drugs to combat enlargement of the prostate, a condition known as benign prostatic hypertrophy.
The prostate is a walnut-size gland in the pelvis; it produces fluid that helps to nourish and transport sperm. Enlargement of the prostate is a non-cancerous condition of unknown cause that is increasingly common over the age of 50.
The prostate surrounds the urethra, the tube that carries urine from the bladder through the penis. As men age, for unknown reasons, non-cancerous tumors often enlarge the prostate and can block the flow of urine through the urethra, leading to more frequent urination and other symptoms.
Other symptoms include hesitancy, or difficulty in starting urination; weak urinary stream; interruption of the stream; feeling of incomplete bladder emptying; and dribbling at the end of urination.
Blockage of urine from enlarged prostates can also cause infections of the urinary system and damage to the bladder and kidneys.
The condition affects an estimated 10 million American men, of whom about 400,000 undergo surgery each year for relief of symptoms.
Marketing approval for Proscar comes at a time when studies have called into question the safety of the standard prostate operation, called a trans-urethral resection.
Proscar is not expected to render prostate surgery obsolete, the Harvard Health Letter said in a recent review of the drug. It is not known how many men will be spared prostate surgery by use of the drug.
The studies that led the FDA to approve Proscar for marketing showed very few adverse effects, said Dr. Elizabeth Stoner, a Merck official.
Of the 1,600 participants, 3.7 percent had impotence, 3.3 percent decreased libido and 2.8 percent a decreased volume of ejaculate. Otherproblems did not occur more often among Proscar users than participants who took a placebo, Dr. Stoner said.
Because only 1,600 patients were included in the scientifically controlled trials that were crucial to marketing approval from the drug agency, other side effects may turn up as more people use the drug.
Adverse effects that occur infrequently may not show up until largernumbers of patients are treated with a drug after it is marketed.
Dr. Stoner and Dr. Edward M. Scolnick, another Merck official, said the company would take extra precautions to alert doctors to potential problems with the drug.
Because Proscar has caused birth defects to male genitalia in rats, Merck is warning men not to take the drug if they are seeking to father a child.