X-Message-Number: 14740
Date: Thu, 19 Oct 2000 14:26:42 -0700 (PDT)
From: Doug Skrecky <>
Subject: terpenes and skin penetration

Title
  Terpenes and the
  lipid-protein-partitioning theory of skin
  penetration enhancement.
Source
  Pharmaceutical Research.  8(1):17-24, 1991 Jan.
Abstract
  A series of terpenes has been assessed as skin penetration
  enhancers towards the model polar penetrant 5-fluorouracil
  (5-FU). Cyclic terpenes were selected from
  the chemical classes of hydrocarbons (e.g., alpha-pinene),
  alcohols (e.g., alpha-terpineol), ketones (e.g., carvone), and oxides (e.g.,
  1.8-cineole, ascaridole). Permeation experiments were performed on excised
  human epidermal membranes and the terpenes
  varied in their activities; alpha-pinene only doubled
  the permeability coefficient of aqueous 5-FU, whereas
  1.8-cineole caused a near 95-fold increase. Essential oils, e.g., chenopodium
  (70% ascaridole), were less effective than the corresponding
  isolated terpenes, 5-FU is less soluble in
  the terpenes than in water, and
  the terpenes did not exert
  their action by increasing partitioning of
  the drug into the membranes as illustrated
  by stratum corneum:water partitioning studies. The
  penetration enhancers increased drug diffusivity through the
  membranes, an effect which correlated empirically with the
  enhancer activities. The principal mode of action of
  these accelerants may be described by the
  lipid-protein-partitioning theory:
  the terpenes interacted with intercellular
  stratum corneum lipids to increase diffusivity, and
  the accelerant effects were not due to partitioning
  phenomena. Keratin interaction was assumed negligible.

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