PERFLUOROCHEMICAL EMULSIONS APPEAR HEADED TO LIMITED INDICATIONS AS BLOOD ALTERNATIVES, ACCORDING TO OTA REPORT: CARBON MONOXIDE POISONING, SICKLE CELL
Potential indications for perfluorochemicals (PFCs) as blood supplements are likely to be limited to carbon monoxide poisoning, sickle cell crisis, cerebral ischemia and patients with religious objections to blood transfusions, according to a study released on Feb. 7 by the Office of Technology Assessment (OTA) entitled "Blood Policy & Technology." "If its use is limited to these clinical situations," the report states, "PFC emulsions will never have a significant effect on the blood transfusion industry." Among perfluorocarbon compounds, Fluosol-DA, developed by Alpha Therapeutic, which filed an NDA last year, is the most thoroughly studied and publicized, the report notes. The Green Cross subsidiary has stated that Fluosol, an oxygen transport agent, is more efficient than natural hemoglobin contained in red blood cells at transporting oxygen from the lungs to other parts of the body and returning carbon dioxide back to the lungs. The company maintains that Fluosol's advantages over red blood cells include a much longer shelf life and its universality as a transfusion agent, thereby eliminating the need for cross-matching tests that regular red blood cell transfusions require. The OTA report notes a number of adverse effects in connection with PFC use as a red blood cell substitute, despite "Japanese clinical experience with Fluosol-DA and reports from some American investigators that have generally given the substitute high marks for safety and efficacy." Chemically inert substances, PFCs "do not appear to be degraded biologically," the report states. "Both animal and human studies have shown that some of the material is retained by the liver and spleen for at least 2 years after a single administration." Because the reticuloendothelial system is involved in PFC clearance, it was suggested and later confirmed that "the saturation of this system would reduce the body's ability to clear other foreign substances such as viruses or bacteria." Of even greater concern, the report states, is the "possibility of chemical carcinogenesis as a result of the long retention time." Furthermore, PFC therapy requires that a patient be given concurrent administration of 60 to 100 percent oxygen in order to deliver enough oxygen to the tissues. The OTA report observes that a high oxygen environment is required because "the highest achievable concentration of PFC in blood is about 20%, and higher concentrations are unstable. Consequently, in order efficiently to utilize the oxygen carrying/delivering capacity of PFC, the patient must be exposed to the risks of a high oxygen environment, which can result in highly reactive oxygen metabolites that can . . . inactivate cellular enzymes, damage DNA and destroy cell membrane architecture." The high oxygen concentration was a concern cited during a FDA advisory cmte. review of the Alpha Therapeutics NDA for Fluosol-DA in October 1983 ("The Pink Sheet" Oct. 31, 1983, p. 12). The OTA report also cites studies which make it "seem likely that the PFC emulsions cause pulmonary dysfunction by activating complement and/or white cells. Release of a substance(s) from damaged leukocytes may then result in both leukycyte and platelet aggregation."
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