A new tolerance test as a guide to clinical heparin therapy.

T HE VALUE of heparin in the treatment of phlebothrombosis and pulmonary embolism has been established,1 and by many it is believed to be the treatment of choice. It is also useful as adjunctive therapy in the treatment of thrombophlebitis, arterial embolism and thrombosis, and coronary heart disease.' Its therapeutic application, however, has been retarded by (1) the individual variation in the response when the dosage was based on weight, (2) the necessity of frequent determinations of coagulation time to disclose the duration of therapeutic effect, and (3) the cost of the medication itself. Factors leading to individual variation in the response to heparin that have been suggested are weight,', age,8 adequacy of renal function, the severity of the thrombotic disease,' and various blood dyscrasias. It has been recommended that all patients weighing 150 pounds and over be given an initial injection of 400 mg. of heparin in a retarding menstruum and that all patients below that weight be given