Photoprotection: updates and controversies

March 1, 2005

Miami Beach — Melanin-inducing drugs represent a systemic approach to photoprotection and also reduce sun-seeking behavior. They will become available within a couple of years, according to James M. Spencer, M.D.

According to Dr. Spencer, who previously directed the division of dermatologic surgery at the Mount Sinai Medical Center in New York City and now has a practice in St. Petersburg, Fla., "Melanin makes a terrific sunscreen. To get more of it naturally, one must sustain UV-induced skin damage to develop a tan. The trick is to get the skin to manufacture melanin without subjecting it to UV exposure."

There are several ways of doing this, Dr. Spencer says. One is via use of the alpha melanocyte-stimulating hormone (MSH). This peptide hormone is released from the pituitary gland after UVB exposure, inducing the production of melanin. An Australian company, Epitan, is currently developing a MSH-based drug for subcutaneous injection once a month.

A third possibility for systemic protection is bicyclic monoterpine diols, which have been proven to induce melanin production in human tissue cultures and in guinea pig skin.

Wash-and-wear protection Better, longer-lasting UVA sunscreens are needed but not likely.

"Because FDA classifies ingredients as drugs, there hasn't been a new active ingredient in almost 20 years," Dr. Spencer says. "Only the vehicle changes."

Paris-based L'Oreal has introduced to the FDA pipeline a prescription formula of its UVA blocking mexoryl, which is widely available throughout most of the world except the United States. Switzerland's Ciba isn't even trying to push its UVA product, Tinosorb, through the FDA.

But, Dr. Spencer notes, "It's already here as a product for clothes. A kid's white cotton T-shirt will let 50 percent of UV radiation through, but if you wash it at the beginning of the summer with Rit Sun Guard, it will add sun protection."

Faulty studies, correlates Prominent physicians in other branches of medicine are questioning the benefits of sunscreens. Dermatologists need to understand their reasoning and why it is fallacious.

"Marian Berwick is an epidemiologist who says people who wear sunscreens get more melanoma," Dr. Spencer says.

Epidemiological analysis is based on the use of retrospective studies. As a body, they have produced conflicting results. Beyond that, the studies are innately flawed. Subjects are self-selected, meaning they've used sunscreens and have melanoma. That implies that they have a fair-skinned, sun-sensitive skin type. Subjects are then asked to look back and recall their sun habits over a period of 40 years. The latency period for melanoma is decades, so subjects would have used low SPF UVB sunscreens with no UVA protection in the 1960's and other less than ideal formulas in later decades.

"Think about it," Dr. Spencer says. "Who wears sunscreen? People at risk. Who gets melanoma? People at risk. The problem is making a cause-effect correlation."

Indoor tanning industry Endocrinologist Michael Holick, M.D. from Boston University argues that there is an epidemic of low Vitamin D and encourages people to get sun exposure so they can increase its production.

As to the "epidemic" factor, Dr. Spencer says, "He raised the definition of what is a normal Vitamin D level for the purpose of the study."