A comparative study of the in vitro dermal absorption of radiolabeled benzophenone through human skin

Octocrylene is a common sun filter ingredient used to protect the skin from damaging UV rays. Benzophenone is an impurity found in formulations containing octocrylene. [ 14 C]-Benzophenone was spiked (0.1 g/L) into 2 commercial sunscreen formulations; Neutrogena (R) Beach Defense Sunscreen Spray Broad Spectrum SPF 70 Aerosol, Neutrogena (R) Ultra Sheer Body Mist Sunscreen Broad Spectrum SPF 30 Aerosol, and an acetone vehicle. The formulations were applied ( ca 2 mu L/cm 2 ) to dermatomed human skin mounted in static diffusion cells in vitro . Receptor fluid was collected up to 24 h post dose. All samples were analyzed by liquid scintillation counting. The dermal delivery of [ 14 C]-Benzophenone was 10.02, 9.04 and 5.19% for the 3 formulations. However, the [ 14 C]-Benzophenone mass balances were low; 81.5, 85.3 and 8.02%, respectively. A volatility test was performed replacing skin with aluminum foil for the sunscreen formulations only. The [ 14 C]-Benzophenone mass balance at dosing was 99% but fell to 56.9 and 60.6% at 24 h post dose, confirming the losses were due to [ 14 C]-Benzophenone volatility. A conservative dermal absorption value of 12.42% was proposed to cover [ 14 C]- Benzophenone containing formulations.