Lecture 15 - Drug Releasing Microspheres

Question 1

Drug Releasing Microspheres

Answer 1

Microspheres are small spheres made of drug and polymer sized 10nm to 2mm in size

Question 2

Advantages of Microspheres

Answer 2

• Mask taste and odor
• Conversion of liquid drug to solid forms for ease of handling
• Drug protection against the environment (moisture, light, O2, etc.)
• Separation of incompatible materials (other drugs and excipients)
• Aid in dispersion of water-insoluble substances in aqueous medium
• May be used to produce targeted medicine

Question 3

Properties of Drug-Releasing Microspheres

Answer 3

• Duration of action
• Controlled release rate
• Drug protection
• Biocompatibility
• Sterilize-ability
• Relative stability
• Water solubility or dispersibility
• Biodegradation

Question 4

Characteristics of Drug-Releasing Microspheres

Answer 4

• Particle size and size distribution
• Polymer molecular weight
• Ratio of drug to polymer (drug loading content)
• Total mass of drug and polymer

Question 5

Types of Drug-Releasing Microspheres

Answer 5

• Microcapsule: consisting of an encapsulated core particle. Entrapped drug completely surrounded by a distinct capsule wall
• Micromatrix: consisting of homogenous dispersion of drug in the particle

Question 6

Polymers for Fabricating Drug-Releasing Microspheres

Answer 6

• Synthetic (non-degradable): PMMA, poly(vinyl-acetate), epoxy polymer
• Synthetic (degradable): PLA, PGA, PLGA, PCL, poly(alkyl cyanoacrylate), polyanhydrides, polyurethane
• Natural (proteins): albumin, gelatin, collagen
• Natural (other): starch, chitosan, alginate, cellulose

Question 7

Degradable Drug Releasing Microspheres

Answer 7

• Release via two different mechanism —> degradation of polymer surrounding the drug, diffusion of drug from the microspheres
• Degradation products must be readily metabolize-able
• Suited to high molecular weight drugs and drugs not soluble in polymer phases

Question 8

Manufacture of Drug-Releasing Microspheres

Answer 8

• Interfacial deposition
• Bulk polymerization
• Suspension polymerization
• Interfacial polymerization
• Spray drying
• Solvent extraction
• Desolvation of albumin