Effect of solute lipophilicity on penetration through canine skin.

OBJECTIVE

To investigate the effect of lipophilicity on the percutaneous penetration of a homologous series of alcohols through canine skin.

DESIGN

Skin harvested from Greyhound thorax was placed in Franz-type diffusion cells and the in vitro passage of radiolabelled (14C) alcohols (ethanol, butanol, hexanol and octanol (Log P 0.19-3.0)) through separate skin sections was measured in replicates of five. Permeability coefficient (kP, cm/h), maximum flux (Jmax, mol/cm2/h) and residue remaining within the skin were determined.

RESULTS

The kP increased with increasing lipophilicity (6.2 x 10(-4) +/- 1.6 x 10(-4) cm/h for ethanol to 1.8 x 10(-2) +/- 3.6 x 10(-3) cm/h for octanol). Alcohol residues remaining within each skin sample followed a similar pattern. An exponential decrease in Jmax with increasing lipophilicity was observed.

CONCLUSION

Changes in canine skin permeability occur with increasing alcohol lipophilicity. This finding has practical consequences for the design of topical formulations and optimisation of drug delivery through animal skin.