Artificial spheres consisting of concentric phospholipid bilayers encapsulating an aqueous PBS (phosphate buffered saline) solution containing clodronate. Liposomes are particles, sized at a max. of 3 micron. They form a suspension in PBS and will tend to precipitate upon storage, forming a pellet on the bottom of the tube or flask. The suspension should be shaken before administration to laboratory animals in order to recover the homogeneous suspension. The concentration of clodronate in the suspension is ca. 5 mg/ml.