IN-VITRO EVALUATION OF DRUG-RELEASE KINETICS FROM LIPOSOMES BY FRACTIONAL DIALYSIS

A new dialysis method was designed with the purpose of studying drug r elease rate from liposomes. The liposomes were diluted directly in the continuous phase and dialysed against a small volume of buffer. The d ialysate was changed at 10 min intervals and the amount of carboxyfluo rescein released was calculated from a standard curve. To evaluate the new method, parallel measurements were recorded with the traditional carboxyfluorescein assay, which is based on direct measurements on lip osomes containing a self-quenching concentration. The new method is ca lled fractional dialysis, and is shown to have sensitivity similar to that of the carboxyfluorescein assay. In certain cases the fractional dialysis method gives a more accurate release profile. It is suggested that fractional dialysis can be a useful alternative to other techniq ues for recording the in vitro release characteristics of specific dru gs from liposomes or other colloidal carriers.