Incorporation rates, stabilities, cytotoxicities and release of liposomal tetracycline and doxycycline in human serum.

Tetracycline and doxycycline were encapsulated in cationic, anionic and neutral liposomes. The amounts of antibiotic encapsulated, the stability of each preparation at 4 degrees C for 4 weeks, and the kinetics of the release of entrapped drug into human sera were assessed by high-performance liquid chromatography. The toxicities of the liposome preparations on human erythrocytes and HeLa 229 cells were evaluated in vitro. The results showed that doxycycline was entrapped more efficiently than tetracycline, and that doxycycline-entrapped liposomes were more stable at 4 degrees C and in human sera, and less cytotoxic than tetracycline-entrapped liposomes.