Current dilemmas in the clinical use of heparin.

The more widespread use of heparin as an effective antithrombotic agent would be greatly facilitated by resolution of the following issues: Clarification of the biological differences between beef and hog heparin. The development of a standard heparin molecule. The modification of heparin for oral use. The availability of a standard in vitro assay of the drug's antithrombotic potential. A meaningful assay of plasma heparin together with a determination of whether or not heparin is present in human plasma in normal and diseased states. Establishment of criterions for determining the proper dosage schedules in various pathological conditions. A reconcilation of USP and International units of heparin.