"Over the last 10 years, there has been an explosion of over-the-counter (OTC) products that contain retinols and retinaldehyde," says Michael H. Gold, M.D., medical director, Gold Skin Care Center and Tennessee Clinical Research Center, Nashville. "It was known early on that we could affect the skin by using metabolites of the retinoic acid derivatives that were more cosmeceutical than prescription in nature." Retinol's metabolites include retinaldehyde, retinol palmitate and retinoic acid. During more than two decades' use, prescription-strength retinoids have proven their mettle in laboratory and clinical situations. The first paper about the use of topical retinoic acid for the treatment of photoaging found mild to moderate improvement in facial wrinkling and smoothing of the skin in patients treated with this drug (0.001 percent to 0.05 percent) for six months (Cordero A. Actua Ter Dermatol. 1983;6:49-54.).More recently, a flood of OTC retinoids has hit the marketplace. Examples include Retinol Actif Pur Anti-Wrinkle Treatment (RoC), Retinol Complex (SkinMedica), TxSystems (.15, .3 and .6 percent retinol, Affirm), Factor-A Cream (Jan Marini) and Retinol Re-Pulp (Biotherm).
In topical skin moisturizers, retinol can perform various functions. It increases epidermal water content by encouraging cellular proliferation and stimulating hyaluronic acid production. This process improves skin hydration when retinol is augmented with humectants and cosmetic emollients. Retinoids pose challenges in formulation, however, due to their inherent photoinstability. Upon exposure to sunlight, they immediately degrade into biologically inactive forms. Hence, they require packaging in light-proof containers. Along with this limitation, it was previously thought that retinol was not biologically active. However, a trial of retinol versus retinoic acid and a placebo found statistically significant increases in epidermal thickening, as well as trace amounts of erythema with retinol and a nearly four-fold increase in erythema for retinoic acid (Kang S et al. J Invest Dermatol. 1995 Oct;105(4):549-556.). Another study found that topical application of retinol (1 percent) to photodamaged skin for one week increased fibroblast growth and collagen synthesis. Retinol also reduced levels of metalloproteinases (Varani J, Warner RL. J Invest Dermatol. 2000; 114: 480-486.). Researchers' understanding of retinaldehyde's role also has expanded. One open-label trial of retinaldehyde 0.05 percent cream in 32 female patients with symptoms of photodamage including elastosis, solar lentigines and wrinkling found that after one month (as well as after three and six months), patients generally were satisfied with the smoothness, comfort and brightness of their skin. The treatment also achieved significant decreases in wrinkle intensity, erythema, telangiectasias and surface roughness of crow's feet (Ochando N, LaGarde JM, Couval E, et al. Nouv Dermatol. 1994; 13: 525-535.). "Retinaldehyde performs similar functions to the prescription products yet has the benefit of being a cosmetically elegant compounded agent," Dr. Gold says. |
