modified release Flashcards
what is modified release?
Modified-release drug delivery refers to the manipulation or modification of drug release from a dosage form (e.g. tablet, pellet, capsule) with the specific aim of delivering API at:
desired rate
pre-defined time points
specific sites in the gastrointestinal tract
what are the types of modified release?
Delayed-release dosage forms – drug is not released immediately but after some time
Gastro-resistant dosage forms (enteric dosage forms) – drug is not released in the stomach at low pH but will be released in the small intestine at higher pH
Extended-release dosage forms (prolonged release or sustained release dosage forms) – drug plasma levels are sustained for longer periods
where are the site of action of oral modified drug delivery
Small intestinal targeted (enteric) systems can release their drug load
in the small intestine
Colonic systems release their drug here and may be able to extend release throughout the large intestine
Gastroretentive systems are retained in the stomach and should release drug
in the stomach and small intestine
Extended release systems can theoretically release drug all through
the GI tract
what are the different profiles for modified release?
- constant release :
- declining release
- delayed release
- bimodal release - delayed release with extended release
- check graph
what is hydrophilic matrix system
Swellable soluble matrices used for extended (sustained) release
Drug is mixed with water-swellable or water-soluble polymer along with other excipients
Effect of polymer nature on drug release characteristics
A fast release can be achieved with:
Polymers with low Mw
Formulations with low percentage of polymer material
A slow release can be achieved with:
- Polymers with high Mw;
- Polymers with high degree of cross-linking;
Formulations with high percentage of polymers;
Incorporation of release modifiers
what is membrane controlled system
Drug core coated with extended-release membrane (dry)
to
Hydrated membrane allows water ingress and drug diffusion
what is osmotic system ?
Drug core coated with semi-permeable membrane (dry)
Water moves through membrane to tablet core solubilising core excipients
and solubilising or suspending drug
Increased pressure in tablet forces solubilised/suspended drug out through a small hole
what is delayed release with gastro resistant coating
Drug core coated with delayed release membrane (dry)
Exposure to correct pH environment dissolves the coating
Exposed drug loaded core dissolves and releases drug
