Formulation and toxicity of liposomes containing rifampicin

RFP was incorporated in liposomes and the effect of lipid composition on incorporation of drug and stability of the vesicles was studied. The amount of RFP incorporated is dependent on the lipid composition, being higher when charged lipids were used. RFP incorporation increased as the fluidity of the vesicles increased. Stability in saline was related to liposomes with high encapsulation of RFP, while stability in serum was superior when phospholipids with a Tc higher than 37°C were used. In vitro RFP and L-RFP were not toxic to erythrocytes; however, L-RFP was less toxic than RFP to CHO cells and to macrophages. In concentrations up to 340 mg x Kg-¹, L-RFP was not toxic to mice.