Modified Release Flashcards
What are the advantages of MR?
- Peaks and troughs minimised
- Improves compliance
- Better safety margin
- Efficient drug use
- Reduced healthcare costs
What are the disadvantages of MR?
- Risk of dose dumping
- Instability of drug
- Expensive
What is delayed release?
Not immediately released but released at a later time e.g. e/c tablets or capsules
What is repeat action MR?
Individual dose released soon after administration, 2nd or 3rd are released at later intervals
What is prolonged release?
The drug is absorbed over a longer period of time but onset is delayed
What is sustained action?
Initial dose gives therapeutic levels then drug is gradually released over an extended period
What is controlled release?
Drug is released at a constant rate and plasma concs don’t vary
What is extended release?
Drug is released slowly and plasma concs are maintained
Which physiochemical properties influence the choice of dosage form?
- aq solubility and stability
- pKa
- Partition coefficient
- Salts
Class I of BSC classification have….
High permeability and high solubility
Class II of BSC classification have….
High permeability and low solubility
Class III of BSC classification have….
Low permeability and high solubility
Class IV of BSC classification have….
Low permeability and low solubility
What are the mechanisms of controlling release?
- Dissolution of active drug
- Diffusion of dissolved or solubilised species
What is the process involved in MR?
- System gets hydrated
- Water diffuses into the system
- Dissolution of drug occurs
- Dissolved drug diffuses out
What are the techniques to build a barrier into oral dosage forms?
- Use of coating
- Embedding drug in wax / plastic matrix
- Microencapsulation
- Ion exchange resins
- Osmotic pumps
What are the components of an oral MR system?
- Active drug
- Release controlling
- Filler
- Matrix / membrane modifier
- Solubilisers
- pH modifier
- Lubricant & flow aid
- Supplementary coating
What is a matrix delivery system?
The drug is uniformly distributed in a matrix which contains a release controlling agent
Describe the process of drug release in a wax matrix
- Drug is in hydrophobic matrix - stays intact
- In aq media, channelling agent dissolves and leaches out - porous matrix is left
- Drug dissolves and diffuses out
- Outer hydrated matrix remains
Describe the process of drug release in a hydrophilic matrix
- Hydrophilic colloids swell in contact with water, forming a hydrated matrix
- The system is made up of drug, hydrophilic colloid, release modifiers and lubricant / glidant
- Hydrated matrix controls diffusion of water into matrix and diffusion of drug though hydrates matrix controls rate of release
- Outer hydrated matrix erodes
Describe drug release from a membrane controlled system
- Membrane has to be permeable through hydration or solubility in other membrane components
- Membrane polymer doesn’t swell on hydration or erode
Describe the process of drug release from an osmotically controlled system
- Drug is in soluble tablet core - solubilises drug in water
- Core is coated with a semi permeable membrane which allows water to pass through into the core
- Hydrostatic pressure build up forcing drug solution through holes
- Rate of release is determined by the rate water can pass through the membrane and how fast the drug solution can pass out
What makes water a suitable diffusing species?
- Characterised and understood
- Release is independent of the drug
- Zero order release profile
- Water diffusion modification is straight forward
What is micro encapsulation?
Coating surface of drug particles with polymer to slow down water penetration and so dissolution
