LOS ANGELES (AP) _ Baldness may be reversed with a new drug that blocks the male hormone testosterone on scalp cells without the side effects of steroid-based drugs, a dermatologist reported.

The drug Cyoctol helped hair growth in 10 of 12 men in a study, said Dr. Richard A. Strick of the University of California, Los Angeles, during a presentation Monday to the American Academy of Dermatology in San Francisco.

Cyoctol, a synthetic compound developed by Los Angeles-based Chantal Pharmaceutical Corp., will be tested by Bristol-Myers Squibb Co. to treat acne and baldness.

Strick's results sound as though they are at least comparable to the hair- growth gains men make with minoxidil, the only drug approved for use in the United States against male pattern baldness and marketed as Rogaine, said Dr. Dowling B. Stough, a dermatologist at the University of Arkansas.

Balding men who used a solution of Cyoctol had 12 percent more hair on a test patch of scalp than they had a year earlier, the Strick study showed. Men who hadn't been treated lost 9 percent of their hair.

Previous studies found that minoxidil resulted in moderate to dense hair growth in 39 percent of men who used it for a year.

Rogaine, a 2 percent minoxidil solution, is the only FDA-approved hair loss treatment and is a non-steroid based drug. It has been on the market for over a year and costs about $60 for a one-month supply.

Strick suggested that perhaps using a combination of Cyoctol and minoxidil could produce dramatic results.

But Strick was cautious about directly comparing Cyoctol's results to those with Rogaine. The studies are not directly comparable, he said, because they analyzed different sections of the balding spot and also because they counted hairs in test sections differently.

In Rogaine studies, the hairs were counted by hand and the Cyoctol test used a new computerized method.

The U.S. Food and Drug Administration also recently approved a Cyoctol analog as an investigational new drug against skin wrinkling.

Stough said the Cyoctol study was small and that baldness remedies frequently don't live up to their early promise.

He also said that if Cyoctol proves effective against baldness it would work best in men in the early stages of hair loss when most follicles have not died.

''You can't grow daffodils without bulbs and you can't grow hair without follicles,'' Stough said.

Additionally, Cyoctol appears to have no side effects like steroid-based preparations. Cyoctol is considered exciting because it doesn't act as a steroid interfering with the body's hormonal balance.

Steroidal substances can reverse baldness, but they can lead to undesired feminine body characteristics, such as cessation of beard growth and enhanced breast development.

Cyoctol blocks the sites on the walls of the scalp cells at which the male hormone testosterone attaches to cause male pattern baldness. When attachment occurs, the hair follicle shrinks and eventually stops growing hair. This type of baldness runs in families and affects about 30 percent of men in the United States.