Thousands of balding American men will begin rubbing their scalps in the coming weeks with the latest remedy for hair loss - Upjohn Co.'s Rogaine.

While its success rate may be as incalculable as the number of hairs you'll wash down the drain during your next shower, Rogaine is the first prescription drug proven to grow new hair.And for that, 50 million Americans may be eternally grateful for its approval by the U.S. Food and Drug Administration.

The drug will start showing up in pharmacies by the end of September. It comes in a bottle with a one-month supply and a choice of rub-on or spray applicators.

It is being sold to pharmacies for $42.50 and will cost consumers about $60. Because it is used primarily for cosmetic reasons, few insurance companies are expected to cover the expense.

Upjohn officials say it may take up to eight months before users see any results. And many Rogaine users will see no change in their rate of hair loss at all.

However, Upjohn officials say, some will see varying amounts of new hair growth, while others will see a decrease in their hair-loss rate or stop losing their hair altogether.

In testing 2,300 men at 27 medical centers, the Kalamazoo-based pharmaceutical firm found 8 percent experienced dense new hair growth, while 31 experienced moderate new hair growth. The remaining 61 percent showed little or no new hair growth.

While a 39 percent success rate for a drug is relatively low, it is considered tremendous in an area where all other remedies have completely failed.