title: Cutaneous drug delivery of capsaicin after in vitro administration of the 8% capsaicin dermal patch system.
abstract: OBJECTIVE
  Epicutaneous application of capsaicin causes a long-lasting analgesic effect by binding to the membrane transient receptor potential vanilloid 1 (TRPV1) on mechanoheat-sensitive C and Aδ fibres, changing axonal integrity and inhibiting neurogenic inflammatory processes. To date, no information is available regarding the cutaneous drug delivery of capsaicin following patch application.
  
  
  METHODS
  Using a Franz diffusion cell, the cutaneous concentration-time profiles 30, 60 and 90 min after application of a patch containing 8% capsaicin (640 µg/cm(2)) on ex vivo thin (mamma) and thick (plantar) human skin were investigated at 32 °C, and additionally at 42 °C for thin skin and 10 °C for thick skin. An HPLC-MS method was used for the analytic detection of capsaicin.
  
  
  RESULTS
  The results show that already after a 30-min application of the 8% capsaicin patch, an equilibrium reservoir can be found in the stratum corneum in both thick and thin skin. Under physiological temperature conditions, a sufficient bioavailability of capsaicin in the cutaneous target compartments can be found. Raising the temperature to 42 °C has no relevant impact on the concentration-time profile, while reducing the temperature to 10°C leads to a significantly lower bioavailability.
  
  
  CONCLUSIONS
  After 30 min of application, a sufficient cutaneous bioavailability of capsaicin is reached in thick as well as thin skin. Whether shorter application times may suffice to achieve therapeutic effectiveness requires further investigation.
authors.affiliation: Department of Dermatology and Venereology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Wohlrab
authors.forename: Reinhard H H
authors.initials: RH
authors.lastname: Neubert
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Heskamp
authors.forename: Julia
authors.initials: J
authors.lastname: Michael
mesh_terms: D000279:Administration, Cutaneous; D000700:Analgesics / Q000008:administration & dosage* / Q000378:metabolism; D001682:Biological Availability; D002211:Capsaicin / Q000008:administration & dosage* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D013058:Mass Spectrometry; D012867:Skin / Q000033:anatomy & histology / Q000378:metabolism*; D012869:Skin Absorption; D013696:Temperature; D057968:Transdermal Patch
chemical_list: D000700:Analgesics; D002211:Capsaicin