Bioequivalence testing of topical dermatological formulations, the gap between science and legislation
- Authors: Schwarb, Fabian P , Smith, Eric W , Haigh, John M , Surber, Christian
- Date: 1998
- Language: English
- Type: Conference paper
- Identifier: vital:6341 , http://hdl.handle.net/10962/d1006608
- Description: Bioavailability concerns for topical dermatological products are complex and it is especially difficult to determine the bioequivalence of similar topical formulations. Since only small amounts of drug dispersed in an appropriate vehicle are applied to the skin, the amount of drug that actually reaches the systemic circulation is often too small to be easily quantified. Additionally, it can be argued that the relevance of any serum/plasma concentration-time curve of a topical agent is questionable, since the curve reflects the amount of drug after the active moiety has left the site of action. For some topical drugs e.g., topical corticosteroids, it is possible to perform a pharmacodynamic bioassay to obtain acceptable bioequivalence data. In this case, the intensity of the side effect of blanching (vasoconstriction) in the skin caused by topical corticosteroids can be measured. The response is directly proportional to the clinical efficacy, and the skin blanching assay has proved to be a reliable procedure for the determination of topical corticosteroid bioavailability. Recently, we had sight of the results of a topical bioequivalence study, which was conducted for the registration of a new generic corticosteroid cream formulation. In this trial the new formulation was compared to two equivalent product from the local market and bioequivalence was demonstrated by the investigators for all three products. These results were examined with interest as the respective reference products have been used repeatedly as standard formulations in our laboratory. However, one of these reference formulations has consistently shown superior bioavailability in our trials, but was not demonstrated to be superior in the study results examined. In the present publication an overview of topical bioequivalence testing in general is given and the difficulties occurring in practice, for topical corticosteroid formulations in particular, are demonstrated.
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Chromametry: measuring precision of diurnal and local variation of human forearm skin colour
- Authors: Schwarb, Fabian P , Smith, Eric W , Haigh, John M , Surber, Christian
- Date: 1998
- Language: English
- Type: Conference paper
- Identifier: vital:6343 , http://hdl.handle.net/10962/d1006610
- Description: Chromameters are compact portable instruments used for the assessment of surface colour based on the tristimulus analysis of a reflected xenon light pulse, and have been used for the quantification of erythema in the study of irritant dermatitis, and corticosteroid-induced skin blanching in the vasoconstriction assay. The variability and the reproducibility of chromameter results were investigated since it is known that the location and application force of the measuring head on the skin and the orthostatic maneuver of the arms influence the colour measurement. Furthermore the diurnal variation and the homogeneity of forearm skin colour were investigated.
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Comparison of visual CR-200 and CR-300 chromameter data obtained from the corticosteroid-induced skin-blanching assay
- Authors: Schwarb, Fabian P , Smith, Eric W , Haigh, John M , Surber, Christian
- Date: 1998
- Language: English
- Type: Conference paper , text
- Identifier: vital:6344 , http://hdl.handle.net/10962/d1006611
- Description: In a recent Guidance document the American FDA recommended the use of a chromameterrather thanthe human eye for the assessment of the pharmacodynamic blanching response produced after topical application of corticosteroids. The purpose of this study was to investigate the appropriateness of the human eye and two types of chromameter for the estimation of skin blanching.
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