Evaluation of Synergistic effects of some currently used sunblocking agents in sunscreen preparations

Synergistic effects between UV absorbers can produce many advantages in sunscreen products such as: decreasing topical irritation, allergic reactions and skin absorption of sunscreen agents.

six currently used UV filters of Eusolex® series (232, 6007, HMS, OS, 4360 and 9020) were studied. Various concentrations from each sunscreen were prepared in isopropyl alcohol and UV spectrums of them were taken in 290-400nm with reference concentration of each UV filters. Six commonly used solvents were used and the best solvent was selected. The best AUC for all sunscreens were obtained from their solutions in isopropyl alcohol as solvent. Single solutions and all probable binary mixtures of them were prepared and compared with another. Synergistic effects of two sunscreen agents in binary systems were compared based on AUCs and their absorption intensity in 310nm.

Maximum synergistic effects in UVB wavelengths was related to Eusolex® 9020- Eusolex® 4360 combination with 10%-90% ratio (about 64% in AUC and 65.7% in 310nm absorption intensity). Combination of Eusolex® 9020 and UVB filters with low weight retios also significantly improved AUC of Eusolex® 9020 in UVA wavelengths (up to 61% in combination with Eusolex® 6007). Eusolex® HMS and Eusolex® OS also showed markedly synergistic effect in combination with Eusolex® 4360 with low ratios (47% and 18.9 % respectively).

these results demonstrated that exactly choosing the type and ratios of UV filters in sunscreens can greatly improve efficiency and decrease effective concentration of formulation active ingredients.