SPF testing an "accurate reflection" of ingredient photostability -- CTFA rep.

SUNSCREEN SPF TESTING ACCURATELY REFLECTS INGREDIENT PHOTOSTABILITY, CTFA said, noting photostability has been a concern raised often with the introduction of more technically advanced UVA sunscreen ingredients such as microfine zinc oxide, microfine titanium dioxide and avobenzone. James Johnson, PhD, University of Tennessee-Memphis College of Pharmacy, speaking on behalf of the Cosmetic, Toiletry & Fragrance Association at a June 3 FDA "feedback" meeting on sunscreens, maintained the current SPF testing method provides "an accurate reflection of the performance of the product."

The photostability of a sunscreen ingredient is accounted for in the SPF test method, Johnson said, since the test measures the ability of a sunscreen to block UV rays. If an ingredient has photostability issues, the sun protection factor of the agent would reflect that fact, he added.

The SPF test accurately predicts the performance of a product because it "simulates or exceeds a longer sunlight exposure" than expected from consumer sunning habits, Johnson explained.

FDA has raised the question of photostability of active ingredients in sunscreens for some time. Specifically, the agency has looked into the stability of titanium dioxide and zinc oxide with particular attention to how stability may be related to particle size and particle coating. The agency also has raised the issue of the photostability and photodegradation of avobenzone ("The Tan Sheet" May 5, 1997, p. 4).

Responding to FDA's questions, Johnson explained that all particle sizes absorb light; however, the wavelengths of absorption will shift as particle size changes. Coating an ingredient does not affect UV absorption, but it does reduce photoreactivity, Johnson said, adding coatings "improve physical properties, which enhance manufacturability, reduce agglomeration and improve feel and compatibility." In addition, the materials used to coat particles demonstrate enhanced photostability for organic actives, such as octyl methoxycinnamate, oxybenzone or avobenzone.

CTFA requested the feedback to discuss current sunscreen formulation issues. Another feedback meeting had been scheduled in April to provide the agency with an "educational discussion of the technical issues and requirements" of sunscreen formulas, but it was canceled by FDA ("The Tan Sheet" May 4, p. 17). CTFA's priority for the meeting was to emphasize to FDA the many technical and scientific advances that have occurred since the advance notice of proposed rulemaking for the sunscreen monograph was first proposed in 1978 and even since the TFM was issued in 1993.

Following Johnson's presentation, FDA Division of Dermatologic & Dental Drug Products Director Jonathan Wilkin, MD, questioned whether the testing method and SPF 2-45 ranking system is truly predictive of a sunscreen's effectiveness at actual use levels. The issue is compounded by the concern over ingredient's photostability and photodegradation, he maintained.

Wilkin noted that SPF calculations are based on an assumed use figure of "an unbelievably large amount of sunscreen." It is "unlikely" that consumers actually are using sunscreens in doses on par with the levels at which the products were tested, he said.

CTFA VP-Science Gerald McEwen, PhD, acknowledged the SPF system has shortcomings, but he suggested it has been beneficial for consumers, who have grown accustomed to the 2 through 45 levels. Through education and use, consumers have come to understand what SPF they need to use, the CTFA exec said. "There hasn't been a better system that has been projected or tested than SPF," he added.

"As bad as it is, it is consistent, and it is the same product to product, and everybody has had to do it the same way," McEwen said. "Now, all of a sudden, [if] we decide that we're going to make it more accurate, more truthful, from that standpoint, you're going to have all new numbers," which would cause consumer confusion.

Schering-Plough Photobiology Research Director Pat Agin, PhD, concurred with McEwen. For consumers, Agin said, the SPF level determines whether a product "maintains its level of protection throughout the expected exposure period." If a consumer gets a sunburn, then he or she will "find a higher SPF or not stay out as long, so [protection] really is, performance-wise, captured in the SPF test."

Acknowledging the arguments on both sides, new Office of Drug Evaluation V Deputy Director Robert DeLap, MD/PhD, asked if another test existed that could replace the SPF test. SPF, he noted, does not capture information such as whether a product tends to "be used more heavily than another product, [or] one product degrades more quickly than another product, or for whatever reason, they just don't perform the same way in actual use." In response, McEwen explained the difficulty of reaching a consensus on testing methods.

The sunscreen meeting was DeLap's first industry encounter in his new position overseeing the OTC drug division. DeLap, formerly the director of FDA's Oncology Drug Products Division, will become acting director of FDA's Office of Drug Evaluation V July 3 following the departure of Michael Weintraub, MD.

The SPF discussion was not resolved before the meeting's conclusion. CTFA VP-Legal and General Counsel Thomas Donegan asked FDA for the next step in the monograph process. FDA Office of Over- the-Counter Drug Products Director Debra Bowen, MD, said FDA is interested in tackling the "remaining issues," and the agency hopes to have an ongoing dialogue with industry. She also noted FDA is working on providing industry feedback on an acceptable UVA testing method.