RELEASE CHARACTERISTICS OF MITOXANTRONE-CONTAINING LIPOSOMES

The release characteristics of mitoxantrone-containing liposomes was s tudied. The effect of lipid composition on the release rate showed an order of positively charged liposomes > neutral liposomes > negatively charged liposomes. This was attributed to the strength of the binding forces involved in the interaction between the drug and lipids. The r elease of mitoxantrone from liposomes after the incorporation of galac tocerebroside demonstrated no dependence on the molar ratio of added g alactocerebroside. This was due to the binding force being insufficien t to influence the release rate of the entrapped mitoxantrone signific antly. The effect of temperature on the release rate revealed that 4 d egrees C may be a suitable temperature for storage of the liposomes du ring the time range studied, since the release rate was slow. At 4, 25 and 37 degrees C, the release profiles fitted a linear concentration- square root of time plot which demonstrated the diffusion-controlled r elease of entrapped mitoxantrone from the membrane matrix. The effect of pH on release showed an increase in release rate with increasing pH . At high pH, partitioning of mitoxantrone into the membrane matrix wa s considerable and drug was released rapidly.