PERCUTANEOUS PENETRATION OF OCTYL SALICYLATE FROM REPRESENTATIVE SUNSCREEN FORMULATIONS THROUGH HUMAN SKIN IN-VITRO

The human skin penetration of [C-14]octyl salicylate from two represen tative sunscreen vehicles was determined in vitro. H-3-sucrose was inc orporated into all formulations and provided a marker for membrane int egrity. When applied as a finite dose in an oil-in-water emulsion vehi cle containing 5% (w/w) octyl salicylate, the average total absorption of C-14 over 48 hr was 0.65 +/- 0.16% of the applied dose (representi ng a total amount permeated of 1.58 +/- 0.36 mu g/cm(2)). When applied as an infinite dose in the oil-in-water emulsion vehicle the average total absorption of C-14 over 48 hr was 0.47 +/- 0.22% of the applied dose (representing a total amount permeated of 27.54 +/- 13.91 mu g/cm (2)). When applied as a finite dose in a representative hydroalcoholic formulation containing 5% (w/w) octyl salicylate, the average total a bsorption of C-14 over 48 hr was 0.59 +/- 0.09% of the applied dose (r epresenting a total amount permeated of 1.58 +/- 0.25 mu g/cm(2)). Whe n applied as an infinite dose in the hydroalcoholic formulation the av erage total absorption of C-14 over 48 hr was 0.23 +/- 0.05% of the ap plied dose (representing a total amount permeated of 11.28 +/- 2.55 mu g/cm(2)). The penetration of [C-14]salicylic acid [applied at a conce ntration of 2.7% (w/w), in the oil-in-water emulsion] was also determi ned. When applied as a finite dose the average total absorption of C-1 4 over 48 hr was 1.14 +/- 0.23% of the applied dose (representing a to tal amount permeated of 1.65 +/- 0.39 mu g/cm(2)). These results sugge st that the in vitro human skin permeation of octyl salicylate is rela tively low. The amounts of octyl salicylate and salicylic acid permeat ed when applied in similar vehicles were remarkably similar over 48 hr (1.58 mu g/cm(2) and 1.65 mu g/cm(2), respectively). This suggests th e possibility that the C-14 label appearing in the receptor fluid may, in both cases, represent salicylic acid. If this is the case, then it is possible that the amount of octyl salicylate permeating through th e skin is much less than that suggested by the data obtained here. Thi s supposition is, however, entirely speculative and has yet to be conf irmed experimentally. (C) 1997 Elsevier Science Ltd. All rights reserv ed.