Effects of acidity, cations and alcoholic fractionation on absorption of heparin from gastrointestinal tract.

Heparin was introduced into the stomach or duodenum of mice separately in doses of ca. 250 mg/kg. A slight anticoagulant effect in the systemic circulation was detected in whole blood clotting times and factor X inhibition. In contrast to most drugs, more heparin was absorbed from the stomach than from the intestine. Suppressing ionization of heparin by simultaneous administration of acid resulted in improved absorption of heparin from the small intestine. Heparin was separated with ethanol into five molecular weight fraction: I, 17 999; II, 13 i99; III, 10800, IV, 8 700; and V, 6 700. Each was introduced into the duodenum of mice with citric acid. The maximum hypocoagulability was produced with fraction IV. When administered in distilled water instead of in citric acid, this heparin fraction did not produce an anticoagulant effect. These studies demonstrated that improvement of heparin absorption from the gastrointestinal tract can be obtained by the combination of suppressing ionization and selecting molecular size.