Systemic and topical drugs for aging skin

Journal of Drugs in Dermatology, August, 2003 by Michael Kockaert, Martino Neumann

Systemic Vitamin E

Vitamin E has been shown to have sunscreen properties. Its UVB absorption peak is 290 nm and it has a very low and broad absorption peak for UVA. Some studies suggest beneficial cutaneous effects of systemic vitamin E. In one study, 8 days of oral vitamin E increased the minimal erythema dose (MED), thereby decreasing susceptibility to UV radiation. In a corroborating study, the combination of oral vitamins E and C for 8 days caused a significant increase of the MED. However, Werninghaus et al. were unable to show that supplementation with vitamin E 400 IU/day for 6 months significantly altered sun damage (14).

The topical use of vitamin E is predominantly supported by in vitro studies. Therefore, additional studies are needed not only to clarify its exact therapeutic role in the skin, but also to determine its optimal chemical form, concentration, and vehicle (17).

Ascorbic Acid (Vitamin C)

Topical vitamin C is water soluble and photosensitive. L-ascorbic acid is the active form of vitamin C and is an essential antioxidant. It acts by neutralizing ROS caused by UV radiation, and as a scavenger of free radicals (18). Vitamin C is not naturally synthesized by the body and therefore adequate dietary intake is required. The role of vitamin C in the processing of procollagen into mature collagen is well-recognized, as vitamin C is a vital co-factor of proline hydroxylase.

In studies of its effects on skin aging, vitamin C has been evaluated in cultured fibroblasts, animal models, and human volunteers. Multiple applications of 10% L-ascorbic acid to porcine skin increased vitamin C levels of the skin by 4- to 40-fold. Pre-treated sites develop reduced erythema after acute UVB but not UVA exposure, and demonstrate significantly fewer sunburn cells after UV irradiation (19). In a study on hairless mice, topical 5% vitamin C reduced wrinkles typical of chronic UVB and UVA exposure (20). Traikovich investigated a topical formulation of vitamin C with tyrosine and zinc, which is also involved in collagen modeling (Cellex-C High Potency Serum[R], Cellex-C International, Toronto, Ontario). After application for 3 months, significant improvement in photodamage was noted (14). These studies are predominantly in vitro and animal studies, investigating the effects of vitamin C after acute UV exposure. In vivo studies on humans and longterm follow up of clinical results are needed to prove the therapeutic and protective effects of vitamin C.

They are many preparations of vitamin C- based products available on the market, but these are predominantly more stable esters and other derivates of vitamin C that more readily penetrate the skin but which are not necessarily converted to the only active vitamin C, L-ascorbic acid.

Hydroxy Acids

Alpha Hydroxy Acids

Alpha hydroxy acids (AHAs) are a group of hydrophilic organic carboxylic acids that have a hydroxy group in the alpha position. AHAs include glycolic acid, lactic acid, citric acid, pyruvic acid, malic acid, and tartaric acid. The most commonly used AHAs are the commercially synthesized lactic and glycolic acids. Glycolic acid is stable, colorless, and water-soluble. The exact mechanisms of action of the AHAs are still unknown. Their effects are pH dependent; there is increased efficacy at lower phs as the free concentration of the acids increases as the pH decreases. Several AHAs also have antioxidative properties, although glycolic and lactic acids do not.