title: Topical skin penetration of diclofenac after single- and multiple-dose application.
abstract: OBJECTIVE
  Transdermal penetration of nonsteroidal anti-inflammatory drugs (NSAIDs) has been shown to be highly variable. The present study was performed to gain insight into the transdermal penetration process of topically applied diclofenac and to test whether transdermal absorption leads to pharmacologically effective concentrations in dermal tissue layers beneath the application site.
  
  
  METHODS
  Six healthy male volunteers participated in this 2-way crossover study and were assigned to 2 treatment groups. In the first group, diclofenac was applied at a therapeutic dose of 60 mg/100 cm2 3 times daily for 4 days with subsequent occlusion with a plastic foil for 4 hours to enhance transdermal drug absorption. After a 1-week wash-out, diclofenac was applied at a single dose of 300 mg/100 cm2 without occlusion. Diclofenac in both groups was applied on a previously shaven area of the thigh. Transdermal penetration was assessed employing in vivo microdialysis.
  
  
  RESULTS
  After multiple-dose administration mean diclofenac concentrations of 0.48 +/- 0.35 ng x ml(-1) were observed in subcutaneous tissue (mean +/- SEM). The mean AUC(subcutis/plasma) ratio of 0.08 +/- 0.02 indicates redistribution of diclofenac from the systemic circulation to the tissue. After single-dose treatment, mean tissue concentrations were 24.26 +/- 46.43 ng x ml(-1) with a mean AUC(subcutis/plasma) ratio of 60.85 +/- 57.59, which suggests direct tissue penetration of diclofenac.
  
  
  CONCLUSIONS
  Transdermal penetration of diclofenac after multiple as well as after single application of the present formulation is highly variable. In addition to other factors influencing the transdermal penetration process, dose and mode of administration are important factors determining whether pharmacologically effective local tissue concentrations are attained.
authors.affiliation: Department of Clinical Pharmacology, Division of Clinical Pharmacokinetics, Vienna Medical University, Vienna, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Dehghanyar
authors.forename: B X
authors.initials: BX
authors.lastname: Mayer
authors.forename: K
authors.initials: K
authors.lastname: Namiranian
authors.forename: H
authors.initials: H
authors.lastname: Mascher
authors.forename: M
authors.initials: M
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Brunner
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D004008:Diclofenac / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004655:Emulsions; D005782:Gels; D006801:Humans; D008297:Male; D017551:Microdialysis; D012869:Skin Absorption; D013997:Time Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004655:Emulsions; D005782:Gels; D004008:Diclofenac