Avobenzone/Zinc/Phenylbenzimidazole Sunscreen Efficacy Data Needed - FDA

Additional efficacy data are needed before FDA can approve the use of avobenzone with zinc oxide and phenylbenzimidazole sulfonic acid in OTC sunscreens, the agency tells Procter & Gamble in a Sept. 15 letter.

The letter responds to a June 24 citizen petition from the company requesting FDA amend the sunscreen tentative final monograph to include 2% to 3% avobenzone in combination with zinc oxide at 2% to 25% and phenylbenzimidazole 1% to 4%.

The petition includes results of three clinical studies on the safety of the combination. The data also were cited by the company in March 1997 comments to FDA urging approval of the smallest possible level of avobenzone in sunscreens to avoid photoallergic responses ("The Tan Sheet" March 17, 1997, p. 6).

Although the data in the petition "are sufficient to support the safety" of the combination, FDA says, P&G included no information on efficacy and "additional efficacy data are needed to demonstrate the UVA radiation protection potential" of the ingredient mix.

In a 1996 proposed amendment to the TFM, FDA said it would allow use of 2%-3% avobenzone alone and in combination with cinnamate, benzophenone, diphenylacrylate and salicylate ingredients. However, safety and efficacy data are required for other combinations.

The TFM proposes an OTC sunscreen ingredient must have an absorption spectrum extending to 360 nm or above "for a product containing that ingredient to display UVA radiation protection claims in its labeling," FDA notes.

The TFM also states the product must demonstrate "meaningful UVA radiation protection by satisfying 'yet to be established' UVA radiation testing procedures that would be included in the monograph."

Until such a method is proposed for inclusion in the monograph, FDA says, "the agency considers testing procedures similar to the methods described by Johnson & Johnson Consumer Products" in a 1986 publication by R.W. Gange et al. and in 1987 by N.J. Lowe et al. "as appropriate for determining the UVA radiation protection potential for a finished OTC sunscreen drug product." Both methods were published in the Journal of the American Academy of Dermatology.

The three studies included in the petition were a human repeat insult patch test, a human phototoxicity study and a human photoallergenicity study. The studies used four sunscreen test products with oil/water emulsion formulas.

The products contained: 7.5% octyl methoxycinnamate and 5% zinc oxide; 3% avobenzone with 7.5% octyl methoxycinnamate and 5% zinc oxide; 3% avobenzone with 7.5% octyl methoxycinnamate, 5% octocrylene and 2% phenylbenzimidazole sulfonic acid; and 3% avobenzone and 7.5% octyl methoxycinnamate.

Results of the repeat insult patch tests in 106 subjects "were interpreted as showing a low irritation potential and no evidence of the induction of elicitation of contact sensitization," FDA notes.

For the phototoxicity study, "none of the test products was associated with either a wheal and flare response or demonstrated a delayed strong erythema and edema response" in the 25 subjects completing the trial, the agency notes. "In fact," according to FDA, "with the exception of a rare equivocal cutaneous response, individual subject responses were all negative."

There was "no evidence of photoirritation or photoallergy on the 26 subjects completing the photoallergenicity trial, FDA says. Altogether, the agency concludes, the studies demonstrate the combination of avobenzone with the test ingredients "have a low potential for irritation, allergenic sensitization and phototoxicity."

The data further suggest the photoallergenic potential of avobenzone is "not augmented by its combination" with zinc or phenylbenzimidazole, FDA states.

The agency requests P&G submit the efficacy data within 30 days. If the information is not received, "we will complete the petition process utilizing only the data submitted to date and will deny your petition without prejudice to a future filing when the data/information become available," the agency says.

P&G does not currently sell traditional sunscreen products in the U.S. However, the firm markets the moisturizer/sunscreen Oil of Olay Daily UV Protectant, with an SPF 15, which contains octyl methoxycinnamate, phenylbenzimidazole and titanium dioxide.