University of Hertfordshire

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From the same journal

New insights into eutectic cream skin penetration enhancement

Research output: Contribution to journalArticle

  • Sarah Fiala
  • Marie Roman
  • Ricardo Inacio
  • Sumaia Mashal
  • Marc B Brown
  • Stuart A Jones
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Original languageEnglish
Number of pages9
Pages (from-to)403-11
JournalInternational Journal of Pharmaceutics
Journal publication date29 Feb 2016
Early online date28 Dec 2015
Publication statusPublished - 29 Feb 2016


The manner in which the eutectic cream EMLA enhances the percutaneous penetration of lidocaine and prilocaine into human skin is still not fully understood. The purpose of this study was to investigate if the modification of drug aggregation played a role in the way EMLA facilitates delivery. Light scattering analysis of lidocaine alone in water gave a critical aggregation concentration (CAC) of 572 μM and a mean aggregate size of 58.8 nm. The analysis of prilocaine in identical conditions gave a CAC of 1177 μM and a mean aggregate size of 105.7 ± 24.8 nm. When the two drugs were mixed at their eutectic 1:1 ratio in water the CAC reduced to 165.8 μM and the aggregate size was 43.82 nm. This lidocaine-prilocaine interaction in water was further modified upon addition of polyoxyethylene hydrogenated castor oil, the surfactant in the EMLA aqueous phase, to produce aggregates of <20 nm. The physical characterisation data suggested that it was the EMLA cream's surfactant that modified the drug molecular interactions in the aqueous continuous phase and caused a 6 fold higher drug penetration through human epidermal tissue compared to the oil formulations tested in this study.


Sarah Fiala, Marie Roman, Ricardo Inacio, Sumaia Marshal, Marc B. Brown, and Stuart A. Jones, 'New insights into eutectic cream skin penetration enhancement', International Journal of Pharmaceutics, Vol. 499 (1-2): 403-411, February 2016, doi: © 2015 Elsevier B.V. All rights reserved.

ID: 10268444