Kinetics of heparin administration.

Many clinicians prefer intravenous administration of heparin sodium because of unpredictable absorption from extravascular sites. In this experimental study, large doses of heparin labeled with sulfur 35 were injected into 34 dogs separated in groups according to dosage and route of administration. Anticoagulation and plasma heparin levels were assessed at half-hour intervals. Intravenous injection produced immediate anticoagulation followed by a predictable decline. Subcutaneous or intramuscular injection resulted in delayed onset and variable levels of anticoagulant activity. The wide range of response following intermittent injection suggests that continuous intravenous infusion offers a more reliable method of treatment.