MRDFs Flashcards
What is a sustained-release system?
Slows down release over an extended period of time
What is an extended release system?
Allow reduction in dosing frequency from that necessitated by a conventional dosage form
What is a delayed release system?
Releases the drug at a time other then promptly after administration
What is targeted release?
Isolates or concentrates the drug in a specific body region, tissue or organ
What is a repeat action formulation?
Usually contains two or more single doses of the drug, one for immediate release and the second for delayed release
What is the difference between SR and XL(extended release)?
The duration of action. Extended release is longer.
At what solubility is it not possible for a drug to be MRDF?
<0.1mg/ml
What are the mechanisms of modified release?
Dissolution system (membrane and matrix)
Diffusion system (membrane and matrix)
Membrane matrix hybrid
Osmotic systems
Explain membrane dissolution.
For one version there is a drug inside with a shell surrounding it - just one layer
For another version there would be multiple layers and the outermost layer acts as the loading dose
Explain matrix dissolution.
Drug is dispersed in a series of different sized granules made of the matrix material
Could be a layered tablet too.
Explain membrane diffusion.
(Reservoir device)
Core is surrounded by a polymeric membrane
Explain matrix diffusion.
(Matrix device)
Drug is distributed uniformly in an inert polymeric matrix
What is the rate limiting step for a diffusion system?
Diffusion of drug through polymer
What is membrane-matrix hybrid for?
Prolonged delivery times
Ex. Nuba ring or IUD
Explain an osmotic system?
Water moves in - dissolves or suspends the drug - membrane is not permeable to the drug - the system pushes the drug out through the orifice
