Studies on the effect of pH on the lipoidal route of penetration across stratum corneum

The effect of pH on the excised skin permeability towards two model lipophi lic compounds was studied in the range of pH 1.0-10.0 and 1.0-12.0, for hyd rocortisone and testosterone, respectively. Suspensions of the model compou nds in appropriate buffers (0.1-0.2 M) were applied to the intact skin, del ipidized skin, skin pretreated with Azone or sodium lauryl sulfate solution and the percutaneous penetration was observed for 28 h. Within the studied pH range, up to pH 11.0 no change in the penetration through the skin and skin accumulation was observed for both compounds. Significant, 3-4-fold, i ncrease of penetration of testosterone was noted only at pH 12.0, however t he change was neither fast not progressing with time. None of the pretreatm ent procedure influenced the observed relationship between pH and skin perm eability. It is concluded that the lipoidal route of penetration is not aff ected by solutions at pH within the range 1.0-11.0. (C) 2001 Elsevier Scien ce BM All rights reserved.