Pharmaceutical Research

, Volume 27, Issue 12, pp 2734–2742 | Cite as

Topical Delivery of a Naproxen-Dithranol Co-drug: In Vitro Skin Penetration, Permeation, and Staining

  • Wing Man LauEmail author
  • Alex W White
  • Charles M Heard
Research Paper



This work probed the topical delivery and skin-staining properties of a novel co-drug, naproxyl-dithranol (Nap-DTH), which comprises anti-inflammatory (naproxen) and anti-proliferative (dithranol) moieties.


Freshly excised, full-thickness porcine ear skin was dosed with saturated solutions of the compounds. After 24 h, the skin was recovered and used to prepare comparative depth profiles by the tape-stripping technique and to examine the extent of skin staining.


Depth profiles showed that Nap-DTH led to a 5-fold increase in drug retention in the skin compared to dithranol. The application of Nap-DTH also demonstrated improved stability, resulting in lower levels of dithranol degradation products in the skin. Furthermore, significantly less naproxen from hydrolysed Nap-DTH permeated into the receptor phase compared to naproxen when applied alone (0.08 ± 0.03 nmol cm-² and 180 ± 60 nmol cm-², respectively). Moreover, the reduced staining of the skin was very apparent for Nap-DTH compared to dithranol.


Topical delivery of Nap-DTH not only improves the delivery of naproxen and dithranol, but also reduces unwanted effects of the parent moieties, in particular the skin staining, which is a major issue concerning the use of dithranol.


anti-proliferative co-drug ester hydrolysis prodrug psoriasis 





Isopropyl myristate


limit of detection


molecular weight




stratum corneum





The authors would like to acknowledge the financial support from Stiefel Laboratories, UK.

Conflict of interest

None declared.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Wing Man Lau
    • 1
    • 2
    Email author
  • Alex W White
    • 1
  • Charles M Heard
    • 1
  1. 1.Welsh School of PharmacyCardiff UniversityCardiffUK
  2. 2.School of PharmacyUniversity of ReadingReadingUK

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