Absorption and tissue distribution of doxorubicin entrapped in liposomes following intravenous or intraperitoneal administration.

Absorption and tissue distribution of free doxorubicin (Dxn) and Dxn entrapped into liposomes have been examined after intravenous (i.v.) or intraperitoneal (i.p.) injection into C57/B1/6 mice. Liposomal encapsulation of Dxn altered its plasma kinetics and tissue distribution. After i.v. administration Dxn in liposomes has a half-life longer than that of free Dxn and it is taken up mostly by tissues rich in reticuloendothelial cells, such as liver and spleen. In the heart and kidney liposomal Dxn reaches a lower concentration than free Dxn. After i.p. injection the tissue distribution of liposomal Dxn is drastically changed. We did not observe the first peak of high concentration in the tissues, the Dxn content in liver and spleen is decreased and its concentration in heart is even more reduced. The results of this study suggest that the route of administration of liposome-entrapped drugs may change both the kinetics of absorption and their tissue distribution and this could result in a different pharmacological effect.