Oral Drug Delivery 2 Flashcards
What is osmotic technology
Controlled delivery of a drug using an osmotic pump
Tablet contains an osmotic-agent which causes an influx of water to the inside of the tablet
Can release drugs with zero order kinetics, independent of concentration
How does osmotic technology work
Osmotic agent acts to draw water from surrounding environment through a semi-permeable membrane
Factors which influence osmotic drug release
Osmotic pressure
Membrane area
Permeability coefficient
Membrane thickness
Drug solubility
What is the relationship between osmotic pressure and drug release
As osmotic pressure increases the rate of drug release of the drug increases
Describe an elementary osmotic pump (EOP)
An EOP is a single layer compressed tablet coated with a semi-permeable polymer (cellulose acetate)
Has one laser drilled hole
How does an elementary osmotic pump (EOP) work
Water is driven into the tablet core through the membrane by the soluble drug
Drug is then released as a soloution
Describe a push-pull osmotic system
Two chamber osmotic pump
Bilayer - push layer and drug layer
Water is drawn in through semi-permeable membrane
When is a push-pull osmotic system used
Used for less soluble drugs or high drug loadings
How does a push-pull system work
Expansion of osmotic ‘push’ layer begins when water is drawn in
This pushes the active drug through the orifice in the tablet
Function of the push layer in a push-pull system
- Generate osmotic potential
- Generate hydrostatic pressure via swelling (to push drug out)
What is a push layer made of?
A highly swellable polymer ( high MW PEO)
An osmogen (NaCl)
There is also option for an immediate or delayed release coating
What are the parts of an OROS
Bilayer (push-pull system)
Semi-permeable membrane
Laser drilled orifice
Aesthetic coating
Commercial example of an OROS
Methylphenidate hydrochloride
CNS stimulant
Used for treat of ADHD
Can be used orally as IR or ER
Advantages of Push-Pull systems
1.Release rate is independent of hydrodynamics
- Release rate is only controlled by osmotic pressure + thickness/permeability of coating
- Therefore fed and fasted states in the stomach do not effect release rate
- Release is not pH dependant
- Avoids problems with establishing in vitro in vivo correlation models for ionisable drugs
- In vitro & in vivo correlation
What is in vitro in vivo correlation (IVIVC)
Predictive model describing the relationship between and in vitro property of a dosage form and an in vivo response
It allows a dissolution test to act as a surrogate for human studies
