Measurement of the bioavailability of aescin-containing extracts

Objective: In horse chestnut seed extracts (HCSE), the triterpene saponin m ixture aescin is considered the active principle. The bioavailability and p harmacokinetics of different HCSE preparations have been studied under sing le and repeated applications using a radioimmunological method (RIA) develo ped to identify beta -aescin, one of the pharmacologically active fractions of the saponin mixture. In this paper, the available pharmacokinetic darn are reviewed and the observed heterogenicity between comparable studies is discussed. Data sources: Pharmacokinetic data from 5 single- and 4 multiple -dose bioequivalence studies with HCSE-containing products, were measured b y the same analytical laboratory using the same RIA. Evaluation: In studies where procedures Me, we identical the pharmacokinetic data of beta -aescin show high variations. Even under steady-state conditions a consider-able v ariability for the same HCSE product is obtained. Conclusion: Formal[ reaso ns like study design and medications can be oiled out as a source of pharma cokinetic variation. Or extracts of herbal drugs like HCS, the relative con centration of the individual saponin fractions can considerably differ from batch to batch. For immunological methods, identification of such antigens with intermolecular variability e.g., the structural aescin analogs, is of unknown validity: Therefore the shape of the concentration-time curve woul d only show an approximation of the rime course bat not for the absolute co ncentrations. A specific validation procedure for the RIA must be developed , otherwise a LC-MS/MS-method of sufficient sensitivity should be elaborate d, (C) 2000 Prous Science. AII rights reserved.