Stratum corneum sampling to assess bioequivalence between topical acyclovir products

Andrea Pensado-Lopez, Wing Sin Chiu, Sarah Cordery, Elena Rantou, A L Bunge, Begona Delgado-Charro, Richard Guy

Research output: Contribution to journalArticlepeer-review

19 Citations (SciVal)


Purpose: To examine the potential of stratum corneum (SC) sampling via tape-stripping in humans to assess bioequivalence of topical acyclovir drug products, and to explore the potential value of alternative metrics of local skin bioavailability calculable from SC sampling experiments. Methods: Three acyclovir creams were considered in two separate studies in which drug amounts in the SC after uptake and clearance periods were measured and used to assess bioequivalence. In each study, a “reference” formulation (evaluated twice) was compared to the “test” in 10 subjects. Each application site was replicated to achieve greater statistical power with fewer volunteers. Results: SC sampling revealed similarities and differences between products consistent with results from other surrogate bioequivalence measures, including dermal open-flow microperfusion experiments. Further analysis of the tape-stripping data permitted acyclovir flux into the viable skin to be deduced and drug concentration in that ‘compartment’ to be estimated. Conclusions: Acyclovir quantities determined in the SC, following a single-time point uptake and clearance protocol, can be judiciously used both to objectively compare product performance in vivo and to assess delivery of the active into skin tissue below the barrier, thereby permitting local concentrations at or near to the site of action to be determined.

Original languageEnglish
Article number180
Pages (from-to)180-196
Number of pages16
JournalPharmaceutical Research
Issue number12
Early online date14 Nov 2019
Publication statusPublished - 1 Dec 2019


  • acyclovir
  • scaled average bioequivalence (SABE)
  • skin
  • stratum corneum sampling
  • topical bioavailability
  • topical bioequivalence

ASJC Scopus subject areas

  • Biotechnology
  • Molecular Medicine
  • Pharmacology
  • Pharmaceutical Science
  • Organic Chemistry
  • Pharmacology (medical)


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