The sickle red blood cell differs physiologically from the normal red cell, especially in fragility and viscocity. The effects whether useful or deleterious of various drugs such as antibiotics or analgesics on the sickle red blood cell are not well investigated, especially the drugs with oxidative potential. Objectives: The present study was carried out to examine the difference in osmotic fragility and deformability between normal and sickle red blood cells before and after, in vitro

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... n with oxidative drugs. Materials and Methods: Blood samples were obtained from sickle cell disease patients (n=39) and normal volunteers (n=19). Sickle hemoglobin was detected by electrophoresis; osmotic fragility was measured by using hypotonic sodium chloride solutions at decreasing concentrations and erythrocyte filterability by filtration method. Different concentrations of aspirin, indomethacin and primaquine were prepared in absolute ethanol and incubated with red cells to measure their effects on fragility and deformability. Results: Osmotic fragility curve was shifted to the left by the sickle red blood cells, the initial haemolysis occurred at concentration of 0.5% for normal and 4.5% for sickle cell. The concentrations of hypotonic saline that caused 50% lysis for the normal and sickle red cell were 0.41% and 0.33% respectively. The erythrocyte filtration time was 83.1± 11.4 seconds for normal and 106.4±23.9 seconds for sickle cell. Aspirin, indomethacin and primaquine produced no effect on osmotic fragility of both normal and sickle cells. Only primaquine at concentration of 2µg/ml caused a statistically significant prolongation in filtration time. Conclusion: The sickle red blood cell resists in vitro haemolysis by hypotonic saline and has longer filtration time than the normal cell; primaquine has deleterious effect on the sickle cell in vitro. This drug should be given with caution to patients with sickle cell disease. Further studies to explore the in vivo effects are recommended.