title: Pharmaceutical foams: are they the answer to the dilemma of topical nanoparticles?
abstract: Nanoparticulate systems have the potential to improve topical drug delivery because of their capacity to enhance drug loading and dissolution, protect chemically unstable therapeutic agents, and improve product aesthetics. However, the commercial use of nanoparticles in topical products is limited because the evidence that they penetrate intact skin is contradictory, and their ability to release active agents in traditional semisolid vehicles is poor. One way to overcome this problem is to formulate nanoparticles in a dynamic delivery system--that is, one that induces a change upon dose actuation so as to promote drug release. Pressurized pharmaceutical foams are one type of dynamic system that can drive a change of state and excipient concentration after dose actuation. This review summarizes the current status of topical products containing nanoparticles, discusses the recent scientific advances in foam production, and investigates the prospect of incorporating nanoparticles into dynamic topical foams. Recent literature suggests that dynamic foams have the potential to break down the nanoparticles loaded within them, improve drug release from nanoparticles, and enhance topical efficacy. Although the published data to support the use of dynamic systems are limited, it is clear that they provide a promising solution to enhance drug release from nanoparticles, and future research work should aim to investigate these systems in more detail.
  
  
  BACKGROUND
  The use of nanoparticulate systems in topical products is limited as skin penetration and release of active agents remains controversial. Pressurized pharmaceutical foams represent a dynamic system characterized by a change of state and excipient concentration after dose actuation. The review summarizes the current status of topical nanoparticles utilizing this delivery system.
authors.affiliation: Pharmaceutical Science Division, King's College London, London, UK.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Zhao
authors.forename: Marc B
authors.initials: MB
authors.lastname: Brown
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Jones
mesh_terms: D000287:Administration, Topical; D004337:Drug Carriers / Q000008:administration & dosage* / Q000737:chemistry*; D004339:Drug Compounding / Q000379:methods*; D005740:Gases / Q000737:chemistry*; D049329:Nanostructures / Q000008:administration & dosage* / Q000737:chemistry*; D004364:Pharmaceutical Preparations / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D005740:Gases; D004364:Pharmaceutical Preparations