An in vivo Method for the Assay of Heparin

Abstract

Summary The anticoagulant activity of heparin has been assayed in sheep, by giving small consecutive doses intravenously at intervals of 4 hours, and determining the coagulation time 4 minutes after injection. A curve is plotted, using doses of a standard heparin varying in strength by 10 to 20 per cent. This is followed by 1 or 2 injections of the unknown heparin in suitable doses. The figures found agree, with a margin of a few per cent., with the theoretical ones. The fresh whole-blood method, using ox blood in vitro, is found to give figures identical with those obtained with the in vivo method. The unreliability of the methods using artificial systems with citrated plasma or salted whole blood, including the U.S.P. XIV method, is discussed. An in vivo method is devised as a reference technique in assaying heparin.