Matrix Tablets Flashcards
Describe matrix tablets
Extended release formulation
Body made of polymer network
Does not disintegrate when hydrated
What are the different types of matrix tablets?
Hydrophilic matrix tablet
Insoluble matrix tablet
What are the 2 drug release mechanisms for matric tablets?
Drug diffusion
Matrix erosion
Describe drug diffusion mechanism
Diffuse out down conc gradient + drug molecules dissolve
Drug molecules at edge of tablet diffuse out first
When does a matrix tablet rely on drug diffusion more?
Less soluble polymer matrix
Describe matrix erosion mechanism
Matrix on outside dissolves = exposes matrix inside
Then inside dissolves
Why may drug release limit drug absorption?
Drug must be released into + dissolved in GI fluids to be absorbed across GI mucosa
Why may drug solubility limit drug absorption?
Low drug solubility in GI fluids associated with slow drug dissolution + thus absorption
Why may GI permeability limit drug absorption?
Low GI mucosal permeability associated with slow drug diffusion across GI mucosa
What type of polymer is a hydrophilic matrix tablet?
Gel-forming polymer
How does hydrophilic matrix tablet work?
Combo of drug diffusion + matrix erosion
Swells upon hydration
Tablet gels from outside in
Gel layer form diffusion barrier
What is the drug release order of hydrophilic matrix tablet?
Zero or first order
What forms a hydrophilic matrix?
Natural gums
Cellulosics
Polyethylene glycol
How do you get a slower release of a hydrophilic matrix tablet?
Higher molecular weight
Higher proportion of polymer content
Higher degree of cross-linking
What does a higher molecular weight of hydrophilic matrix tablet cause?
Greater swelling
Less erosion
Slower release
What is the polymer of insoluble matrix tablet?
Polymethacrylates
How does insoluble matrix tablet work?
Diffusion-based system only
Drug incorporated in pores
As H2O enters pores, drug dissolves + diffuses out through H2O-filled pores
What is the drug release order of the insoluble matrix tablet?
First order only
Why is the insoluble matrix tablet first order only?
Matrix NOT dissolved
= expelled out of body in the stool
Describe how the osmotic pump system works
Laser-drilled hole in semi-permeable coat
H2O enters via permeable coating
Push compartment swells, pushing drug out through orifice
What are the risks with them?
If the rate-controlling membrane or polymer matrix fail
= dose delivered prematurely
= over dose
= dose dumping
