Volume 32, Issue 4, Page 13 (April 2001)

Lipoic acid has been proposed as a new antioxidant agent to treat and prevent the aging of skin. It also represents a new option for treating and preventing fine lines and pigmentation abnormalities such as solar lentigines.

Lipoic acid has been shown to be effective for treating inflammatory diseases. Therefore, it may decrease the inflammation that many experts believe leads to accelerated skin aging. This theory is championed by Dr. Nicholas Perricone of Meriden, Conn., who has done extensive research on lipoic acid for cosmeceutical indications.

Formerly known as thioctic acid, [7,8-14C] rac-a-lipoic acid is an essential cofactor in mitochondrial dehydrogenases. It is an octanoic acid, an eight-carbon version of carboxylic acid combined with cysteine.

The effectiveness of lipoic acid is believed to be due to its by-product, dihydrolipoic acid (DHLA). Although DHLA has a more powerful antioxidative effect than lipoic acid, it is very unstable and is oxidized in the skin within minutes of application.

Lipoic acid has become popular due to the fact that it is absorbed in a stable form and after entrance into cells, is immediately converted to DHLA (Biochem. Biophys. Res. Commun. 42[1]:98-104, 1994).

One thing that makes lipoic acid different is that it is both water soluble and lipid soluble. Most antioxidants available in cosmeceutical vehicles are one or the other.

Researchers have identified and emphasized four principal antioxidative properties of lipoic acid:

• The capacity to chelate metals.
• The ability to scavenge reactive oxygen species.
• The ability to regenerate endogenous antioxidants such as vitamins C and E.
• The ability to repair oxidative damage (Gen. Pharmacol. 29[3]:315-31,1997).

In human skin, topical application of 3% lipoic acid in a lecithin base has been shown to reduce UVB-induced erythema twice as quickly as skin treated with lecithin base alone (Biochem. Pharmacol. 52[4]:627-33, 1996). This indicates that topical application of lipoic acid could prevent free radical damage to skin, reducing the effects of photoaging and carcinogenesis.

Studies have shown that lipoic acid is well absorbed by the skin. Dr. Maurizio Podda and his associates at the University of California, Berkeley, looked at the capacity of lipoic acid to penetrate the skin in anesthetized hairless mice.

They applied 5% lipoic acid in propylene glycol for 30 minutes to 4 hours. They found the rate of absorption into the skin to be constant 30 minutes after application, reaching the maximum concentration by the 2-hour mark (Biochem. Pharmacol. 52[4]:627-33, 1996).

Lipoic acid is beneficial for the treatment of pigmentation disorders in much the same way glycolic acid and salicylic acid are. Lipoic acid enhances desquamation by decreasing keratinocyte cohesiveness, allowing superficial, melanin-containing cells to slough off.

When lipoic acid is used in conjunction with a tyrosinase-inhibiting agent such as hydroquinone, azelaic acid, or kojic acid, the cells that are sloughed off are replaced by cells that contain less melanin. The addition of a good sunscreen to this regimen makes it an effective alternative treatment for hyperpigmentation disorders.

As a cosmeceutical, lipoic acid is available in many different forms and vehicles in concentrations ranging from 1% to 7%.

Recommended concentrations for treating aging skin range from 1% to 4%. For treating scars, 5%-7% concentrations are recommended (Medicina [B. Aires] 43[3]:285-90, 1983).

Lipoic acid is available for home use as a nutritive cleanser, an emollient, or an oral supplement. Emollient vehicles include creams, lotions, and gels.

In addition to its consumer popularity, lipoic acid is also a tool for the cosmetic dermatologist's practice. It can be used as a superficial peel to resurface the skin in a manner similar to glycolic acid. And its proven efficacy in reducing UVB-induced erythema could lead to its emergence as a treatment of postlaser erythema.

When instructing patients on how to use lipoic acid products, advise them to start with an every-other-day schedule—especially if they are using retinoid products simultaneously. If no side effects occur, usage can be increased to twice a day by week 3.

Patients may feel a slight tingling sensation upon applying lipoic acid. This will decrease after a few seconds and disappear within minutes.

Lipoic acid can cause a significant amount of inflammation, so patients should be followed closely. Fine skin lines may improve after a few weeks; however, the reduction of fine lines may be due to inflammation. Makeup can be applied immediately over lipoic acid without interfering with its antioxidant benefits.

Currently, there are no published, double-blind, clinical trials demonstrating the efficacy of lipoic acid for any indication. However, Dr. Valeria Taborda of Bauru, Brazil, and I are currently studying its use for improving photodamaged skin. Preliminary results of our unpublished trial indicate that home use of topical lipoic acid has comparable results to home use of glycolic-containing products.

Lipoic acid is a potent antioxidant that represents a promising option in the treatment of aging skin and, therefore, should achieve increasing consideration and importance in the practice of cosmetic dermatology.

DR. LESLIE BAUMANN is director of cosmetic dermatology at the University of Miami. Melissa Chesler, a research fellow at the university, contributed to the column. To respond to this column, write to Dr. Baumann at our editorial offices.

© 2001 International Medical News Group. Published by Elsevier Inc. All rights reserved.