Lysis of human red blood cells in the presence of various cosolvents

Two in vitro methods are presented which enable the evaluation of virtually any solution for the production of lysis in intramuscular and intravenous administration. These methods differ from the standard hemolytic method in that the RBCs and ghosts, which remain after mixing test solution with RBCs, are washed with normal saline. The intact RBCs are then lysed with water. Since the final measurement is always made in pure water, the effects of vehicle components on the absorbance or solubility of hemoglobin are virtually eliminated. These methods were used to evaluate propylene glycol (PG), dimethyl sulfoxide (DMSO), ethanol (EtOH), polyethylene glycol 400 (PEG 400), dimethyl acetamide (DMA), and dimethyl isosorbide (DMI) for hemolytic potential in comparison to a reference of 10% EtOH, 40% PG, and 50% water. Measured LD 50 values for lysis of RBCs are expressed as total volume percent of cosolvent in whole blood. These values are: 39.5% DMI, 37.0% DMA, 30.0% PEG 400, 21.2% EtOH, 10.3% reference, 5.7% PG, and 5.1% DMSO.