Module 2A modified release systems

Question 0

Define: delayed release

Answer 0

Are enteric coated tablets or capsules designed to pass through the stomach unaltered, so that the medication is released in the intestinal tract.
Enteric coats are used to either protected against breakdown of a drug by gastric acid or to protect the stomach from irritating drugs.

Question 1

Define: extended release (2)

Answer 1

Designed to release their medication in a controlled manner at a predetermined rate, duration and location to achieve and maintain optimum therapeutic levels of the drug.
AIM: to reduce dosing frequency

Question 2

Define: repeat action

Answer 2

Dosage form that usually contains 2 single doses of medication. One immediate release the other delayed release.
Eg: two layer tablets

Question 3

Define: targeted release

Answer 3

Targeted release describes drug release directed towards isolating or concentrating a drug in a specific part of the body for absorption or drug action.

Question 4

Describe essential characteristics required by drugs to be suitable for incorporation into extended release oral dosage forms (5)

Answer 4

1. They exhibit neither very slow nor very fast rates of absorption or excretion (4-6hrs)
2. Uniformly absorbed from GI tract
3. Administered in relatively small doses
4. Posses a good margin of safety
5. Used in chronic rather than acute conditions

Question 5

Discuss the advantages of extended release oral drug delivery systems (5)

Answer 5

Advantages:

  - less fluctuation in drug blood levels 
  - reduced frequency of dosing
  - more convenient and compliant
  - reduced side effects
  - reduced of health care costs

Question 6

Discuss the disadvantages of extended release dosage forms (4)

Answer 6

1. Loss of flexibility in adjusting the drug dose or regimen
2. Risk of dose dumping due to a failure of technology
3. Constraints on the types of drugs that are suitable candidates
4. Limited maximum period of therapeutic response to ~12hrs

Question 7

Outline technologies used to achieve extended release oral solid dosage forms (8)

Answer 7

1. Coated beads, granules, microspheres
2. Multitablet system
3. Micro encapsulated drug
4. Drug-hydrophilic matrix system
5. Drug-inert plastic matrix
6. Complex formation
7. Ion exchange resins
8. Osmotic pump

Question 8

Describe oral osmotic drug delivery system (draw as well) (4)

Answer 8

OROS: composed of a core tablet surrounded by a semipermeable membrane coating with a 0.4mm hole produced by a laser.
The core tablet has 2 layers:
-one contains the active
-the other a polymeric osmotic agent (push layer)
This system operates on the principle of osmotic pressure
When the tablet is swallowed the semipermeable membrane permits water to enter from the patients stomach into the core tablet, dissolving and suspending the drug.
As pressure increases in the osmotic layer it pumps the drug solution through the whole in the side of the tablet.

Question 9

Describe technologies used to achieve delayed release oral solid dosage forms (4)

Answer 9

Specifily coated to remain intact in stomach and release in the intestines 
Enteric coated can be:
pH dependent 
Time dependent
Enzyme dependent