Formulation of Advanced or Complex Medicines 27

Question 1

What is the function of a swellable matrix?

Answer 1

Swell!
Sometimes following gel formation dissolve

Question 2

Give examples of excipients that are swellable matrices

Answer 2

Give examples of excipients that are swellable matrices

Question 3

What are the advantages of a matrix modified release oral dosage form?

Answer 3

Comparatively simple
Excipients are cheap and systems easy to manufacture
Can obtain different types of release profile
Can contain a high drug loading

Question 4

What are the disadvantages of a matrix modified release oral dosage form?

Answer 4

Release of drug is dependent on 2 diffusion processes
- water in
- drug out
Erosion of outer layer complicates release profile
Scale-up can be a problem and need good batch reproducibility

Question 5

Give two examples of diffusion controlled modified release oral dosage forms

Answer 5

Reservoir device
Matrix system

Question 6

Give two examples of dissolution controlled modified release oral dosage forms

Answer 6

Repeat Action vs sustained action
Osmotically controlled system

Question 7

How do dissolution controlled modified release oral dosage forms work?

Answer 7

Enteric coating
- drug release is sustained according to the different dissolution rates of the coating(s) around the active ingredient

Question 8

What is the structure of dissolution-controlled systems?

Answer 8

Can be
- drug particles
- inert particles coated with drug
- conventional tablet coated with a dissolving film
- drug embedded/dispersed in a slowly dissolving matrix

Can be complex systems
- alternating layers of rate-controlling coats
- groups of beads with different coatings

Or can be as simple as leaving out the disintegrant in a tablet formulation

Question 9

What are nanoparticles used for in dissolution controlled modified release oral dosage forms?

Answer 9

Becoming popular for poorly soluble new CNS drugs
- more controlled dissolution
Can reduce inter-patient variability
Can ensure rapid early absorption
- very important
- pain control

Question 10

What is a repeat-action dosage form?

Answer 10

Repeat action tablet or gelatin capsule
- usually contains 2 (or 3) doses of drug
- the first to give a rapid onset of action
- the second is often delayed by use of an enteric coat

Question 11

How can the release profile of a repeat-action dosage form be controlled?

Answer 11

Varying coat thickness or its solubility
Use a number of different size releasing units to prepare tablets

Question 12

How does an osmotically controlled system work?

Answer 12

Driven by the difference in osmotic pressure inside and outside the dosage unit
Require dissolution of drug inside the dosage unit
Convective transport of a saturated drug solution out through a single hole in a semi-permeable membrane
- water in but not water out
- drug can’t get out in water

Question 13

How can the coating of an osmotically controlled system be broken?

Answer 13

Inclusion of an expansion layer which swells on contact with water
Increased volume of water inside

Question 14

What are the advantages of osmotically controlled devices?

Answer 14

Diffusing species is water
Release is independent of active agent properties
- wide range of drugs can be used
Constant delivery rates higher than those achievable by diffusion

Question 15

What are the disadvantage of osmotically controlled devices?

Answer 15

Size of hole is critical
Laser drilling is costly
Need careful control of coating and coat characterisation
Potential for dose dumping
Can be very expensive
Quality control is more extensive
Failure of pin hole/system can lead to dose dumping

Question 16

What is an ion exchange system?

Answer 16

Water insoluble resins containing salt forming groups
- resin mixed with drug solution to form drug-charged resin which dried and bound into a tablet