Microsphere Formulation
A drug delivery system where the peptide is encapsulated in tiny biodegradable polymer spheres (typically 10-100 micrometres) that gradually degrade at the injection site, releasing the drug at a controlled rate. Octreotide LAR and some leuprolide depot formulations use PLGA microsphere technology for monthly dosing.
Technical Context
PLGA microsphere manufacturing involves: dissolving the peptide in aqueous solution, emulsifying with PLGA dissolved in organic solvent (oil-in-water or water-in-oil-in-water emulsion), solvent removal (evaporation/extraction), and collection/drying of microspheres. Particle size (typically 10-100μm) is controlled by emulsification parameters. The peptide is entrapped within the polymer matrix and released as PLGA undergoes hydrolytic degradation (ester bond cleavage → lactic and glycolic acid monomers → further degradation to CO2 and H2O). Release kinetics: initial burst (surface peptide), diffusion phase, and degradation-controlled phase. Octreotide LAR microspheres require specific reconstitution technique — the suspension must be prepared and injected promptly to prevent settling and incomplete dosing.