Release and Skin Permeation of Scopolamine From Thin Polymer Films in Relation to Thermodynamic Activity

J Pharm Sci. 2016 Apr;105(4):1496-500. doi: 10.1016/j.xphs.2016.02.004.

Abstract

The object was to demonstrate if the diffusional flux of the drug out of a drug-in-adhesive-type matrix and its subsequent permeation through an excised skin membrane is a linear function of the drug's thermodynamic activity in the thin polymer film. The thermodynamic activity, ap(*), is defined here as the degree of saturation of the drug in the polymer. Both release and release/permeation of scopolamine base from 3 different poylacrylate pressure-sensitive adhesives (PSAs) were measured. The values for ap(*) were calculated using previous published saturation solubilities, wp(s), of the drug in the PSAs. Different rates of release and release/permeation were determined between the 3 PSAs. These differences could be accounted for quantitatively by correlating with ap(*) rather than the concentration of the drug in the polymer films. At similar values for ap(*) the same release or release/permeation rates from the different polymers were measured. The differences could not be related to cross-linking or presence of ionizable groups of the polymers that should influence diffusivity.

Keywords: activity; solubility; transdermal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesives / chemistry*
  • Adjuvants, Anesthesia / administration & dosage*
  • Adjuvants, Anesthesia / pharmacokinetics
  • Administration, Cutaneous
  • Animals
  • Drug Delivery Systems / methods*
  • Mice
  • Permeability
  • Polymers / chemistry*
  • Pressure
  • Scopolamine / administration & dosage*
  • Scopolamine / pharmacokinetics
  • Skin / metabolism
  • Skin Absorption*
  • Solubility
  • Thermodynamics

Substances

  • Adhesives
  • Adjuvants, Anesthesia
  • Polymers
  • Scopolamine