Vitamin D, mexoryl

A This is an important question in light of the current controversy regarding the need for sun exposure to maintain adequate vitamin D levels. I should first mention that many dermatologists will be surprised to find that almost all of their patients show vitamin D levels below the normal range. This is not quite as surprising when one realizes that the minimum laboratory normal lower limit value for vitamin D has been raised.

I believe this change in the laboratory normal range is partially responsible for the current media issues regarding vitamin D deficiency in this country. Thus, replacement of body vitamin D stores followed by daily oral vitamin D supplementation is currently recommended by many endocrinologists. The body stores can be replaced with prescription vitamin D in the dose of 50,000 IU for two weeks followed by daily supplementation of 800 IU. This will supply all the vitamin D required for the mature adult to maintain good bone health and eliminate the need for sun exposure. There is no doubt in my mind that oral vitamin D supplementation and the use of sunscreens is a better way to maintain bone health than frequent unprotected sun exposure.

A Let's answer this question by first analyzing the ingredient mexoryl and then discussing the two forms available on the international market for sun protection. Mexoryl is the new sunscreen active popular in Europe and South America, which has not been approved for use in the United States. Nevertheless, many high-end pharmacies, spas, dermatologists and Internet drug services are selling mexoryl-containing sunscreens supposedly illegally in this country. Mexoryl, originally developed by scientists working for L'Oreal to stabilize avobenzone, is also known as Parsol 1789. Avobenzone is an excellent broad-spectrum photoprotectant that was developed by Roche, however, it is somewhat photo unstable. Meaning that the avobenzone degrades rapidly when exposed to UVA radiation increasing the need for frequent reapplication.

One molecule of avobenzone can absorb UVA radiation only once, making it inactive from that time forward as opposed to zinc oxide or titanium dioxide that can reflect UVA radiation over and over again with minimal decay. All of the avobenzone applied to the skin is virtually rendered inactive after five hours of UVA exposure.

Mexoryl effectively extends the life of avobenzone and two formulations were developed. Mexoryl SX is a water-soluble form that is suitable for day wear sunscreen formulations. This would include sunscreen-containing moisturizers and facial foundations. Mexoryl XL is an oil soluble form that is suitable for water-resistant sunscreen formulations, including those worn on the beach and during vigorous physical exercise.

It is unclear whether mexoryl will ever be approved for use in the United States. Mexoryl approval could occur in two different manners, depending on the wishes of L'Oreal and its sister company Galderma. Mexoryl could be approved under an investigational new drug (IND) submission to the Food and Drug Administration as a new prescription sunscreen ingredient or it could be approved as a new ingredient added to the Sunscreen Monograph as an over-the-counter drug. Both of these approval routes are expensive. Japan has solved the problem of sunscreen approval by classifying them as quasi-drugs while other countries consider sunscreens to be cosmetics eliminating regulation. One of the major problems with sunscreen approval in the United States is the challenge of dealing with the outdated monograph process. The monograph idea was perfectly acceptable when created, since few new chemicals of value with demonstrable safety were being introduced into the marketplace. Now, the ingenuity of the cosmetic chemist has produced valuable new ingredients that cannot be used due to the monograph process. Our regulatory bodies perform a valuable public service, but must keep up with the technologic times.

Zoe Diana Draelos, M.D., is a clinical associate professor of dermatology, Wake Forest University School of Medicine, Winston-Salem, N.C., and primary investigator, Dermatology Consulting Services, High Point, N.C. Questions may be submitted via e-mail to zdraelos@northstate.net.