The permeability coefficient, K p , of pure unbranched alkanoic acids (Cz-C,) applied to isolated porcine skin, reached a maximum in the solubility parameter ( 8 2 ) range of 9.7-10 ~a l ' / ~/ c m ~/ ~.
When these and other penetrants were delivered from a solvent vehicle, the following linear relationships could be demonstrated: ( a ) between log K , and the molar attraction constant of the penetrant [ 6 2 0 2 or (-Eu)'/2] for six unbranched and six branched acids delivered from 1 M solution in n-heptane; ( b ) between K , and the partial molal volume difference in n-heptane (62 -0;) for the unbranched acids; and (c) between K , and ( 6 2 -0 s ) for propionic acid delivered from 1 M solutions in nine solvents having 61 values in the range 7.4-12.7 crn3I2. Drug penetrability in a given series could be assessed from knowledge of the excess free energy of the penetrant in the delivery system used.
Keyphrases 0 Absorption, percutaneous-alkanoic acids in vitro, porcine skin, permeability coefficients, application of regular solution theory 0 Alkanoic acids-percutaneous absorption in uitro, porcine skin, permeability coefficients, application of regular solution theory Permeability coefficients-alkanoic acids through porcine skin, in vitro percutaneous absorption, application of regular solution theory