Controlled drug delivery Flashcards
What is the transit time of small intestine
Short
Why is Controlled release needed
To target a site of action
If there’s toxicity in GIT
Acid Lability
What are the 4 main mechanisms for Controlled release
Monolith device
Membrane limited systems
Multi particulate systems
Gastro-retentive systems
Explain how the monolith device works
Block of material- drug released slowly
Hydrophilic more common- drug released via gel layer formed when in contact with water
What material is used for monolith device
HPMC
What is the equation for controlled release tablets
%of drug released = k x square root of time
How does a membrane limited system work
Drug in reservoir and release limited by rate-limiting step
Core coated with film
Water in , drug out
What material is used for membrane limited systems
Eudragits (ethyl cellulose)
What is the danger of membrane limited systems
Dose dumping
Positives and negatives of membrane limited system
+ = many drugs can be used
cheap
~zero order release
- = if using osmosis controlled then laser for hole is expensive
dose dumping
How does a multiple-particulate system work?
More than 1 unit contained in capsule
positives and negatives of multiple particulate system
+ = less likely for dose dumping
can mix diff. units with diff. film thickness
reduces irritation
- = expensive
small spheres escape stomach quickly
What material is used for multiple particulate systems
eudragits, ethyl cellulose
How do gastro retentive dosage forms work
eg Gaviscon
Floats
bioadhesive
swells
or extendable
Positives and negatives for gastro retentive dosage forms
+ = increase adherence
targets stomach diseases/ illnesses
- = dehydrates mucosa
