Bioequivalence testing of topical dermatological formulations, the gap between science and legislation

Schwarb, F.P. and Smith, E.W. and Haigh, J.M. and Surber, C. (1998) Bioequivalence testing of topical dermatological formulations, the gap between science and legislation. In: Proceedings of the 2nd World Meeting on Pharmaceutics, Biopharmaceutics and Pharmaceutical Technology. APGI, Châtenay-Malabry, France, pp. 811-812.

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Abstract

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.

Item Type:Book Section
Uncontrolled Keywords:bioequivalence; testing; topical dermatological formulations
Subjects:Y Unknown > Subjects to be assigned
Divisions:Faculty > Faculty of Pharmacy
ID Code:633
Deposited By: Prof John Haigh
Deposited On:31 May 2007
Last Modified:06 Jan 2012 16:18
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