Pharmacological actions of central nervous system depressants given intravenously as suspensions

Three central nervous system (CNS) depressants, methohexital (sodium), midazolam (maleate), and flunitrazepam, were given intravenously to rabbits in equimolar doses as suspensions and solutions. The mean diameters of the particles in the suspensions were 770, 840, and 460 nm, respectively. The CNS actions were verified by recording the bioelectrical activity of the precentral cortex. The suspensions were tolerated well. There were no differences in onset, duration, and maximal intensity of action between suspension and solution of each drug. The results of this study should facilitate pharmacological studies of drugs acting on the CNS that are insoluble in water.