Evaluation of Oral Urea in the Management of Sickle Cell Anemia

Abstract

The rationale for the use of urea in treating or preventing sickle cell vaso-occlusive episodes is based on Murayama’s hypothesis that hemoglobin S molecules, when deoxygenated, polymerize by means of hydrophobic interaction to form microfilaments and microcables which result in distortion of the red cell (Murayama, 1971). The resulting sickle forms may then occlude the microcirculation with subsequent infarction and necrosis. Almost all of the clinical manifestations, symptomatology, and ultimate progressive disability seen in individuals with sickle cell anemia are the direct result of such vaso-occlusive phenomena. (Diggs, 1965). Nalbandian postulated that any agent or condition which could diminish hydrophobic bond strength should interfere with the mechanism of tetramer polymerization of hemoglobin S, and thus prevent or reverse sickling of hemoglobin S erythrocytes. (Nalbandian, 1971a). In a search for such an agent Nalbandian and co-workers found that urea was not only effective in disrupting hydrophobic bonds, but also possessed other desirable properties for in vivo use. These included molecular dimensions small enough to pass through the membrane of the intact red blood cell (rbc) and the fact that urea is water soluble, metabolically inert and non-toxic.