Studies lasting almost two years have confirmed earlier findings that tretinoin, a vitamin A acid derivative, is able to help smooth skin wrinkles and repair some damage of aging and sunlight exposure.

Dr. John J. Voorhees of the University of Michigan Medical School said Monday that use of tretinoin cream on a small group of patients over 22 months has shown the drug can cause the skin to repair some of the marks left by time and to erase some blemishes."Whatever type of wrinkling that has occurred, treatment from (tretinoin) will improve," Voorhees said in a report at the annual meeting of the American Academy of Dermatology.

In a report published last January in the Journal of the American Medical Association, Voorhees said that a four-month study using tretinoin cream caused fine skin wrinkles to disappear on the face and arms.

He said Monday that study has now been extended to 22 months and that 21 patients have remained in the experiment from the beginning.