Definition of Microspheres:
Microspheres are small, spherical particles, typically ranging from a few micrometers to a few millimeters in size.
They contain active ingredients uniformly distributed within a polymer matrix or as a core-shell system.
Types of Microspheres:
Matrix Systems:
The drug is homogeneously distributed throughout the polymer matrix, with no distinct core-shell separation.
Reservoir Systems:
The active ingredient forms a core surrounded by a polymer shell, allowing controlled release as the shell degrades or permits diffusion.
Release Mechanism:
Primarily diffusion-controlled, where the drug is gradually released as the polymer matrix swells or erodes.
Applications:
Used in:
Injectable formulations
Oral sustained-release tablets
Inhalable systems
Targeted drug delivery