Abstract 1662: Biologic Characterization of Contaminants and Impurities in Recalled Heparin
During the period of November 2007 to February 2008, hypotensive and anaphylactoid reactions and deaths were reported to the FDA in patients who were administered procedural heparin. Because of increased demand for heparin and related products, sub-standard heparin has been introduced in the US market. The FDA recalled the suspected products which later were determined to contain over-sulfated chondroitin sulfate (OSCS) as an intentional contaminant. The influence of the main contaminant on blood coagulation and its interaction with heparin has not been addressed. To understand the anticoagulant effects of OSCS and other impurities in the recalled batches of heparin OSCS. Various batches of contaminated heparin were subjected to heparinase 1 and/or nitrous acid digestion to isolate OSCS. Further purification included ethanolic precipitation and ion exchange chromatography. While the main contaminant was OSCS, it was present as a heterogeneous mixture (mean mw 17.8 kDa) and had a similar molecular profile as heparin. A significant amount of dermatan sulfate (up to 10%) and chondroitin sulfate (up to 5%) were also found. OSCS exhibited modest anticoagulant activity (20 – 40 USP U/mL) in the PT, aPTT, ACT, anti-IIa, and USP assays (without anti-Xa activity), However, OSCS mixed with heparin produced a strong interaction resulting in a disproportionately high anticoagulant activity. A 50% mixture of OSCS with heparin resulted in 100–190 USP U/mL (assay dependent). OSCS produced strong interaction with PF4 and was neutralizable by protamine sulfate. Contaminated heparin, contaminant-free heparin, and OSCS produced concentration-dependent activation of the contact system resulting in the generation of kallikrein and bradykinin. In animal models, contaminated heparin produced stronger bleeding and antithrombotic actions in comparison to contaminant-free heparin. These data indicate OSCS exhibits strong interactions with heparin. In addition, other impurities in heparin may also contribute to the biologic actions of this agent.