Modified release oral drug delivery

Question 1

What are the advantages of modified release drugs?

Answer 1

Peaks and troughs are minimised, Improved compliance, Lower side effects, less drug used

Question 2

What is meant by a delayed release formulation?

Answer 2

The drug is not released immediately, but at a later time

Question 3

What is meant by a repeat action delivery system?

Answer 3

A dose is released on administration, second and third doses are released at later intervals

Question 4

What is meant by a prolonged release delivery system?

Answer 4

The drug is absorbed over a longer period of time than from a conventional dosage form.

Question 5

What is meant by a sustained action delivery system?

Answer 5

An initial release of drug that is sufficient to provide a therapeutic dose soon after administration, then a gradual release over an extended period

Question 6

What is meant by an extended release drug delivery system?

Answer 6

Slow release of the drug

Question 7

What is meant by controlled release of the drug?

Answer 7

Release of drug at a constant rate and provides plasma concentrations that remain invariant with time

Question 8

What types of dosage forms are there?

Answer 8

single unit, multiple unit, modified release

Question 9

What types of dosage form leave the stomach rapidly?

Answer 9

solution and pellets

Question 10

How long can single unit doses stay in the stomach for?

Answer 10

10 hours if delivery system taken with heavy meal

Question 11

The intestinal transit time is approx. how long?

Answer 11

3 hours

Question 12

Which factors make it difficult to achieve ideal drug release rates and constant plasma levels?

Answer 12

Variable physiological conditions of GIT

Clearance rate can be patient dependent e.g. age, race, etc

Disease status

Food/diet intake

Question 13

What is the ideal BCS classification of a drug?

Answer 13

Class I with high solubility and high permeability

Question 14

How do MR formulations provide slow release of maintenance dose?

Answer 14

Embedding drug into a wax or plastic matrix, incorporation in an osmotic pump, microencapsulation, chemical binding to ion exchange resin

Question 15

Which headings are MR oral delivery systems grouped under?

Answer 15

monolithic/matrix systems, reservoir or membrane controlled systems

Question 16

What is the difference between drug release from a hydrophilic matrix and a membrane controlled delivery system?

Answer 16

In a hydrophilic matrix, the colloids swell in contact with water to form a hydrated matrix which controls the further diffusion of water into the matrix and this controls the rate of release of drug. In a membrane controlled delivery system, there is no swelling on hydration of the membrane and the membrane does not erode.

Question 17

How do osmotically-controlled systems work?

Answer 17

Osmotic pressure is used as the driving force to generate a constant rate of drug release. The membrane permits the passage of GI fluid, but not drug or electrolyte

Question 18

In an osmotically-controlled system, what is the rate of drug release governed by?

Answer 18

The rate at which water is able to pass through the membrane and how fast drug solution can pass out

Question 19

First order release is what you want to achieve with modified release systems. True or false?

Answer 19

False

Zero order

Question 20

The main purpose of using an oral delayed release tablet is to prolong the half-life of a drug. True or false?

Answer 20

False

To provide site specific absorption of drug

Question 21

How does microencapsulation alter the release of tablet?

Answer 21

Simply coating (e.g. by spray) the surface of a drug particles with polymer to slow down water penetration and hence dissolution

Question 22

How do ion exchange resins alter the release of drugs?

Answer 22

Ionised drug binds to a polymeric resin through opposite charges. Drug resin is then milled to obtain a smaller particle size

Question 23

Which ion exchange resins do basic drugs bind to?

Answer 23

Cationic exchange resins

Question 24

Which ion exchange resins do acidic drugs bind to?

Answer 24

Anionic exchange resins

Question 25

How do KCl extended release tablets work?

Answer 25

Each crystal of KCl is microencapsulated with an insoluble polymeric semi-permeable membrane. As fluids pass through the membrane KCl dissolves within the microcapsules and is released through the membrane over 8-10 hours

Question 26

Which causes more gastric irritation slowK or MicroK?

Answer 26

SlowK

Question 27

How do MST continus suspension granules work?

Answer 27

Morphine bound to ion exchange resin beads. Morphine is displaced by sodium and potassium ions present throughout the GIT