Browsing by Subject "BCS"

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  • Saarikko, Elina (Helsingfors universitet, 2010)
    Biopharmaceutical Classification System (BCS) is a scientific framework for classifying drug substances based on their aqueous solubility and intestinal permeability. When combined with dissolution of the drug product, the BCS takes into account three major factors that govern the rate and extent of drug absorption. For a BCS biowaiver, the in vitro dissolution study may be used as a surrogate for in vivo bioequivalence studies. Currently, BCS I drugs are accepted as biowaiver candidates by EMEA, FDA and WHO. EMEA and WHO also accept class III drugs in some conditions. The main difficulty in classifying drugs according to BCS is the determination of permeability. Biopharmaceutics Drug Distribution Classification System (BDDCS) was introduced to provide a surrogate for permeability. If the major route of elimination is metabolism, then the drug exhibites high permeability. There are two parts in this master thesis. BCS and BDDCS are discussed and evaluated in the literature part. The focus is in the BCS III drugs. The purpose of the experimental part is to evaluate BCS III drug, hydrochlorothiazide as a biowaiver candidate. Solubility of the drug substance and dissolution of the drug product was determined. Aim of the permeability studies with Caco-2 cells were to study if hydrochlorothiazide permeates by passive diffusion across the monolayer. Importance of paracellular diffusion was evaluated by opening tight junctions with EDTA. Influence of dissolution rate was evaluated by theoretical simulation. According to the results of this study, hydrochlorothiazide has good solubility in aqueous buffer. It has been reported to diffuse passively across the epithelial cells but in this study permeability increased when concentration decreased. This may be due to active transport. Hydrochlorothiazide diffuses partially through the tight junctions. Dissolution of the hydrochlrothiazide tablet was very rapid. Drug eliminates almost entirely by metabolism, it is also BDDCS class III drug. EMEA and WHO accept BCS III drugs as biowaiver candidate if dissolution rate is very rapid. According to this, hydrochlorothiazide could be suggested as a biowaiver candidate. There are also other issues to be considered, for example excipients used in tablets. Since hydrochlorothiazide has been discovered to be absorbed in the upper part of the small intestine, the influence of excipients is especially important. This possible influence should be evaluated before the final decision of biowaiver.