"Estimation of the stratum corneum diclofenac reservoir by chromametry"

Clijsen, Ron and Clarys, Peter and Baeyens, Jean Pierre (2010) "Estimation of the stratum corneum diclofenac reservoir by chromametry". In: The 6th European EISCSA Congress, 20-21 May 2010, Saint Etienne, France.

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INTRODUCTION: The stratum corneum (SC) is known to form a reservoir for topically applied substances. Investigations on the reservoir function of SC are important in order to understand the pharmacokinetics of topically applied substances, and to elaborate the optimal treatment procedure. The aim of our study was to estimate the reservoir properties of Diclofenac (DF) after a single topical application with and without occlusion. METHODS: A group of 14 healthy volunteers (females and males, aged 20-25) free of local or systemic treatment with any drugs participated in this study. During the duration of the experiments the volunteers were asked to maintain their daily activities but to abstain swimming and extensive showering. A 1% DF (Voltaren Emulgel®, Novartis) formulation (12mg) was applied on the volar forearms on randomized defined circular skin areas of 7cm2. The product was applied for 20 minutes under two different conditions at the same time; passive diffusion under a semi occlusive sponge and an application without occlusion. Bioavailability of DF in the SC under the two conditions was assessed by quantification of a methyl nicotinate (MN) induced erythema at respectively 48 and 72 hours post DF application. When DF is present in the stratum corneum the nicotinate response is depressed in a concentration dependent way. The response of the MN induced erythema was quantified with the Minolta Chromameter operating in the L*a* b* mode. Measurements were carried out before DF application; prior to MN application and at every 5 minutes until 1 hours post MN application. Kinetics were compared using the MANOVA procedure. RESULTS: a* in function of time at respectively 48 hours post DF application is represented in graph 1. At both measurement times (48 and 72 hours post DF application) the MN response was weaker at the DF treated skin sites compared to the MN response at the untreated control site. There was no difference between open or semi-occlusive application, neither at 48 hours nor at 72 hours post DF application. When comparing the application modalities at the different time intervals (48 hours versus 72 hours post DF application) no significant differences were found. Conclusion: Up to 72 hours post an initial open or semi occlusive DF application we found an inhibition of the MN response. This can be used as an indication for the presence of active DF in the stratum corneum. The reservoir formation seems to be independent of the application modality. Evaluation of the MN response at longer time intervals post DF seems necessary to estimate the duration of the DF reservoir. Keywords: skin, Stratum corneum, reservoir, penetration, diclofenac

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