Targeted release Flashcards
What is the rationale for colonic drug delivery?
Treatment of local diseases (Crohn’s, IBD), systemic absorption of proteins in colon, extended absorption in gut, chronopharmacology (timing drug delivery).
What potential formulation approaches are there for colonic drug delivery?
Rectal delivery (reaches distal areas of GIT), pH sensitive systems (will dissolve at certain pH), utilising colonic bacterial azoreduction (bacteria cleaves N=N bond in polymer), utilising colonic bacterial polysaccharidases (colon is location of polysaccharide degradation)
Describe an experiment that could be performed to determine the transit of controlled-release oral formulations in human volunteers.
Gamma scintigraphy. This uses radio-isotopes to track controlled release drug formulations through the GIT.
What controls gastric emptying into the small intestine?
The duodenum
What are the potential challenges to oral drug delivery?
Drugs having a bitter/unpleasant taste, Dysphagia, Low oral bioavailability
What does uncontrolled drug delivery mean?
There are no constraints on the medicine and it is given in its normal capsule/tablet form.
What does controlled drug delivery mean?
There is some form of constraint on the release of the medicine. This may include: constant release (Metformin PR) or targeted release (enteric coated).
What does a monolith system refer to?
A block of material that will allow the drug to be released and dispersed slowly. They may also be referred to as CR matrices.
Why is hydroxypropylmethylcellulose (HPMC) useful in monolith drug systems?
On contact with water/biological fluids, the outer layer is hydrated into a gel which allows for drug diffusion out of the swollen matrix, the matrix is then eroded throughout the gastric residence time.
What is a key point about monolith system drug kinetics?
There is a square root relationship between release and time (Time is square rooted).
What does a membrane limited system refer to?
A system that controls drug release via a rate-limiting membrane. This means that the drug is immobile until the membrane is penetrated allowing drug diffusion from the reservoir inside the system, this is usually done by water penetration.
What does an osmotic pump system refer to?
A system that utilises osmosis to push the drug out of the system due to the build-up of osmotic pressure inside. There is a small hole in a water insoluble coating which solubilises the inside of the system. As influx of water increases, pressure builds which expels the drug.
What might hinder the use of osmotic pump systems?
The holes for water are difficult to create and therefore expensive, the coating must be consistent and have high integrity or else the tablet will fail, dose will be dumped and it will be ineffective.
What is a multiple-particulate system?
A capsule containing small pellets of drug in a shell that can be made of different materials. The use of pellets can contribute to better drug deposition in the gut.
What is a gastro-retentive formulation?
A formulation of drug that is created to remain in the stomach for longer than usual, thus avoiding gastric emptying. They may be buoyant, bioadhesive, or have the ability to swell.
