To the Editor.—
The official United States Pharmacopeia monograph on heparin sodium provides an assay for standardizing the potency of the drug by comparing its capacity to prolong the clotting time of blood with that of USP sodium heparin reference standard. Protamines are not involved in this assay. The USP monograph further provides purity tests to preclude contaminating proteins, extraneous nitrogen content, pyrogens, and excessive acidity or alkalinity, volatile substances, and residue on ignition. Moreover, USP requires that the manufacturer label the product to indicate the organ and species from which it is derived.If improved standards, assay methods, purity tests, or labeling safeguards are available to enhance the clinical utility and efficiency of heparin sodium, USP should be pleased to receive explicit recommendations buttressed by verified scientific data.