Gaschromatography of clemastine. A study of plasma kinetics and biological effect

A method for estimation of clemastine in human plasma has been developed. By chronic acid oxidation the drug is degradated to chlorobenzophenone, which can then be analysed by gas-liquid-chromatography using electron-capture detection. The plasma levels of clemastine after oral and i.v. administration have been studied. Using different methods for extraction of the drug from plasma a metabolic degradation of the pyrrolidine part of clemastine is demonstrated. The metabolite proposed may be biologically active. The plasma level of the drug was found to be directly related to its biologic effect, measured as inhibition of the histamine-induced flare in human skin.