Modified Release

Question 1

What are the advantages of MR?

Answer 1

• Peaks and troughs minimised
• Improves compliance
• Better safety margin
• Efficient drug use
• Reduced healthcare costs

Question 2

What are the disadvantages of MR?

Answer 2

• Risk of dose dumping
• Instability of drug
• Expensive

Question 3

What is delayed release?

Answer 3

Not immediately released but released at a later time e.g. e/c tablets or capsules

Question 4

What is repeat action MR?

Answer 4

Individual dose released soon after administration, 2nd or 3rd are released at later intervals

Question 5

What is prolonged release?

Answer 5

The drug is absorbed over a longer period of time but onset is delayed

Question 6

What is sustained action?

Answer 6

Initial dose gives therapeutic levels then drug is gradually released over an extended period

Question 7

What is controlled release?

Answer 7

Drug is released at a constant rate and plasma concs don’t vary

Question 8

What is extended release?

Answer 8

Drug is released slowly and plasma concs are maintained

Question 9

Which physiochemical properties influence the choice of dosage form?

Answer 9

• aq solubility and stability
• pKa
• Partition coefficient
• Salts

Question 10

Class I of BSC classification have….

Answer 10

High permeability and high solubility

Question 11

Class II of BSC classification have….

Answer 11

High permeability and low solubility

Question 12

Class III of BSC classification have….

Answer 12

Low permeability and high solubility

Question 13

Class IV of BSC classification have….

Answer 13

Low permeability and low solubility

Question 14

What are the mechanisms of controlling release?

Answer 14

• Dissolution of active drug

- Diffusion of dissolved or solubilised species

Question 15

What is the process involved in MR?

Answer 15

• System gets hydrated
• Water diffuses into the system
• Dissolution of drug occurs
• Dissolved drug diffuses out

Question 16

What are the techniques to build a barrier into oral dosage forms?

Answer 16

• Use of coating
• Embedding drug in wax / plastic matrix
• Microencapsulation
• Ion exchange resins
• Osmotic pumps

Question 17

What are the components of an oral MR system?

Answer 17

• Active drug
• Release controlling
• Filler
• Matrix / membrane modifier
• Solubilisers
• pH modifier
• Lubricant & flow aid
• Supplementary coating

Question 18

What is a matrix delivery system?

Answer 18

The drug is uniformly distributed in a matrix which contains a release controlling agent

Question 19

Describe the process of drug release in a wax matrix

Answer 19

1. Drug is in hydrophobic matrix - stays intact
2. In aq media, channelling agent dissolves and leaches out - porous matrix is left
3. Drug dissolves and diffuses out
4. Outer hydrated matrix remains

Question 20

Describe the process of drug release in a hydrophilic matrix

Answer 20

1. Hydrophilic colloids swell in contact with water, forming a hydrated matrix
2. The system is made up of drug, hydrophilic colloid, release modifiers and lubricant / glidant
3. Hydrated matrix controls diffusion of water into matrix and diffusion of drug though hydrates matrix controls rate of release
4. Outer hydrated matrix erodes

Question 21

Describe drug release from a membrane controlled system

Answer 21

1. Membrane has to be permeable through hydration or solubility in other membrane components
2. Membrane polymer doesn’t swell on hydration or erode

Question 22

Describe the process of drug release from an osmotically controlled system

Answer 22

1. Drug is in soluble tablet core - solubilises drug in water
2. Core is coated with a semi permeable membrane which allows water to pass through into the core
3. Hydrostatic pressure build up forcing drug solution through holes
4. Rate of release is determined by the rate water can pass through the membrane and how fast the drug solution can pass out

Question 23

What makes water a suitable diffusing species?

Answer 23

• Characterised and understood
• Release is independent of the drug
• Zero order release profile
• Water diffusion modification is straight forward

Question 24

What is micro encapsulation?

Answer 24

Coating surface of drug particles with polymer to slow down water penetration and so dissolution