Interaction of Quinidine with Phospholipids. I

The effect of quinidine and its isomer, quinine, on the thermotropic behavior of phosphatidylcholine vesicles was studied by differential scanning calorimetry (DSC) and fluorescence polarization measurement. The effect on the release rates of carboxfluorescein and acrinol was also investigated. Quinidine and quinine lowered the lipid trasition temperatures and increased the release of the drugs contained in the lipid vesicles. This effect seems to be due to a fluidizing action on the membrane.