Vitamin A acid: clinical investigations with 405 patients.

Vitamin A acid (retinoic acid) is less toxic than vitamin A and seems to be an important advance in dermatology. Its therapeutic effect was investigated in clinical studies involving 405 patients. Biochemical investigations have shown that the administration of vitamin A acid is associated with elevation of serum levels of retinol and carotene and after high dosage symptoms develop identical with hypervitaminosis A. Several possibilities regarding the mode of action of vitamin A acid are discussed.