Microparticles containing active ingredients, agents containing these microparticles, their use for ultrasound-controlled release of active ingredients, as well as a process for their production

A composition which comprises microparticles in a pharmaceutically acceptable solution, wherein:

• the microparticles have the form of a biodegradeable polymer shell enclosing a core;
• the composition contains at least one pharmaceutically active ingredient essentially only within the core of said microparticles and not in the polymer shell or in the solution outside the polymer shell;
• the microparticles also contain in the core a pharmaceutically acceptable gaseous phase;
• the biodegradeable polymer shell is comprised of a protein, gelatin, fibrinogen, collagen, crosslinked polypeptide, reaction product of proteins with polyethylene glycol, starch, chitin, chitosan, pectin, polylactic acid, copolymer consisting of lactic acid and glycolic acid, polycyanoacrylate, polyester, polyamide, polycarbonate, polyphosphazene, polyamino acid, poly-ξ-caprolactone, copolymer consisting of lactic acid and ξ-caprolactone or a mixture thereof;
• and
• the microparticles are capable of being destroyed in vivo by application of ultrasonic energy such that the at least one pharmaceutically active ingredient is released in vivo.