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.