Oversulfated Chondroitin Sulfate Is Not the Sole Contaminant in Recalled Heparin Preparations.

Abstract 1070

Poster Board I-92

Several reports have suggested that the contaminated heparin recalled by the regulatory bodies including the FDA and European community contained varying amounts of oversulafted chondroitin sulfate (OSCS). The reported adverse reactions and death were solely attributed to the presence of OSCS including the activation of the contact system and the generation of vasoactive mediators such as the bradykinins. The pathophysiologic nature of the adverse reactions were complex and multifactorial and not all of the adverse reactions can be attributed to an activation of the contact system by OSCS. To further explore the nature of the contaminants, several batches of contaminated recalled heparin from various sources were analyzed utilizing chemical and biologic methods. Such additional contaminants as high molecular weight dermatan sulfate (HDS), oversulfated heparan sulfate (OSHS), oversulfated dermatan sulfate (OSDS), oversulfated heparin sulfate (OSH) and other various forms of glycosaminoglycans were found in the contaminated heparin products. OSCS, HDS, OSDS and OSHS produced activation of prekallikrein to kallikrein in whole blood and plasma systems at variable rates as measured by monitoring the generation of kallkrein. All of the agents produced an activation of the complement system which was not proportional to the generation of kallikrein system. All of the contaminants were capable of forming complexes with PF4 and all produced ¹⁴C serotonin release in the HIT screening analysis. Variable anticoagulant responses occurred with each agent and were mediated via heparin cofactor II. Supplementation of various oversulfated agents showed that OSCS, OSDS and OSH produced comparable anticoagulant effects. Interestingly in the heptest, none of the oversulfated contaminants with the exception of heparin produced any anticoagulant effect. In the thrombin time assasy, OSH produced the strongest anticoagulant effects whereas OSDS and OSCS produced relatively weaker effects, while OSHS did not produce any effects. In the amidolytic anti-Xa assay, only OHS produced an inhibition of this enzyme, whereas, all of the other agents had no effects. In the anti-IIa assay all agents produced variable inhibitory effects. OSH produced the strongest inhibition with an IC₅₀ of 4 ug/ml. OSCS inhibited this enzyme with an IC₅₀ of 7.2 ug/ml and OSDS showed an IC₅₀ of 11 ug/ml. The IC₅₀ of OSHS was > 20 ug/ml. All agents showed a relatively weak affinity for antithrombin (AT). All agents were resistant to the actions heparinase-1. Both OSCS and OSDS produced an inhibition of heparinase. These results clearly suggest that heparin contaminants represent a heterogenous group of oversulfated GAGs which may mediate multiple pathophysiologic responses. The complex and diversed spectrum of the pathologic events in patients exposed to these contaminants need additional investigations to fully understand their adverse clinical effects in vivo.