title: Percutaneous permeation modifiers: enhancement versus retardation.
abstract: BACKGROUND
  The use of permeation enhancers to compromise the barrier properties of skin has been ongoing for decades. However, toxicity associated with certain xenobiotics has led to the development of permeation retardants. Since both enhancers and retardants modify the surface layer of the skin, they can be collectively referred to as penetration modifiers.
  
  
  OBJECTIVE
  This review attempts to outline a comparison of two types of penetration modifiers: enhancers and retardants.
  
  
  METHODS
  In addition to reports of enhancement and retardation by modifiers, we also provide evidence as to why we should group these compounds together, since we have found that retardants can become enhancers in different formulation environments.
  
  
  CONCLUSIONS
  Since modifiers influence drug delivery, further exploration of these compounds is required to understand their modifying action on the properties of skin.
authors.affiliation: Ernest Mario School of Pharmacy, Department of Pharmaceutics, Rutgers-The State University of New Jersey, New Jersey Center for Biomaterials, Life Science Building, 145 Bevier Road, Piscataway, NJ 08854, USA.
authors.forename: Diksha
authors.initials: D
authors.lastname: Kaushik
authors.forename: Priya
authors.initials: P
authors.lastname: Batheja
authors.forename: Brian
authors.initials: B
authors.lastname: Kilfoyle
authors.forename: Vishwas
authors.initials: V
authors.lastname: Rai
authors.forename: Bozena
authors.initials: B
authors.lastname: Michniak-Kohn
mesh_terms: D000279:Administration, Cutaneous; D000465:Algorithms; D000818:Animals; D002626:Chemistry, Pharmaceutical; D005079:Excipients / Q000494:pharmacology*; D006801:Humans; D006860:Hydrogen Bonding; D004364:Pharmaceutical Preparations / Q000737:chemistry / Q000378:metabolism*; D012869:Skin Absorption / Q000187:drug effects*
chemical_list: D005079:Excipients; D004364:Pharmaceutical Preparations