Abstract: The present invention describes a surprising new and effective pharmaceutical composition comprising microparticles and a pharmaceutically acceptable carrier. In particular, the present invention describes a pharmaceutical composition containing microparticles off a matrix material into which is infused a therapeutic agent. The present invention further provides a method of infusing a therapeutic agent such as a protein or peptide into a matrix material to form microparticles containing said therapeutic agent by employing a compressed solvent which is normally gaseous at ambient temperature and pressure. A method is also disclosed of treating or preventing a disease in a mammal by administering to said mammal through a mucosal membrane an effective amount of a pharmaceutical composition comprising microparticles containing a therapeutic agent which effectively treats the disease or disorder.