Effect of piracetam on sickle erythrocytes and sickle hemoglobin.

Piracetam, 2-oxo-1-pyrrolidine acetamide, inhibits sickling of red cells containing sickle hemoglobin (Hb S). The concentration required for 50% inhibition is about 300 mM. Addition of piracetam into the supersaturated Hb S solution in concentrated phosphate buffer prolongs the delay time prior to gelation. Piracetam shifts the oxygen equilibrium curves of blood toward the right, with a stronger effect at higher piracetam concentrations. Piracetam increases the viscosity of oxygenated cells but reduces the relative viscosity of deoxygenated sickle cells. The mechanism for the antisickling effect of piracetam will be discussed.