Oral Drug Delivery 1

Question 1

What is the most frequently used administration route and why

Answer 1

Oral - simplest, most convenient and safest route

Question 2

In what ways is the stomach not designed for absorption

Answer 2

Variable volume
Hydrochloride acid creates an acidic environment (most drugs are weak acids)

Question 3

Advantanges of oral route

Answer 3

ACE

Acceptability
Compliance
Ease of administration

Question 4

Disadvantages of oral route

Answer 4

BAD

Bioavailability varies
Adverse environment in the stomach
Difficulties swallowing

Question 5

How is the stomach a bad environment for absorption?

Answer 5

Acidic environment
Gastric emptying
Bioavailability varies with changing conditions in the stomach

Question 6

What is a modified release product

Answer 6

MR products modulate absorption by altering the site of release of the drug
Drug only releases when it reaches a targeted section of the GI tract

Question 7

Therapeutic benefits of modified release products

Answer 7

Improved efficacy
Increases patient convenience
Reduce adverse effects
Optimises drug performance

Question 8

Objective of a MR product

Answer 8

The objective of an MR product is to alter the drug input (in time or space) in the intestinal lumen

Question 9

3 common ways of MR

Answer 9

TED
Targeted release
Extended release
Delayed release

Question 10

3 release mechanism offered by oral MR products (physical mechanisms) & examples of each

Answer 10

Diffusion - reservoir system
Dissolution - matrix dissolution system
Osmotic - basic osmotic pump

Question 11

Polymers used in 3 release mechanisms

Answer 11

Dissolution - HPC & HPMC
Diffusion - EC
Osmotic - cellulose acetate (semi-permeable membrane)

Question 12

Polymers for extended release systems

Answer 12

Hydrophilic matrices are used for ER
Polymers used are water soluble and gel forming

Question 13

Mechanism for hydrophilic polymers in ER systems

Answer 13

Matrix makes contact with intestinal fluid
Hydrophilic polymer on surface of matrix hydrates to form a gel layer
Gel layer controls fluid entry and controls release

Question 14

What is hypromellose

Answer 14

Hypromellose is a a water-soluble, hydrophilic polymer commonly used in ER preparations
It goes by the name methocel E & K

Question 15

Advantages to using hypromellose

Answer 15

Rapid and uniform formation of gel
Good physical properties
Low cost
Ease of manufacture

Question 16

Steps in drug release from a matrix tablet (4 steps)

Answer 16

Initial wetting - to form the gel layer
Expansion of gel layer - water permeates tablet increasing the thickness of the gel layer
Tablet erosion - outer layer becomes fully hydrated, then dissolves in gastric fluid
Soluble drugs diffuse through gel layer; Insoluble drugs are release by erosion

Question 17

What equation is used to model release date

Answer 17

Korsmeyer-Peppas equation
Mt/Mo = kt^n

N - release exponent
K - diffusion rate constant
T - time of release
Mt/Mo - fraction of drug release

Question 18

How do different n (release exponent) values affect release data modelling

Answer 18

n = 1 - Drug release is independent of time (zero order kinetics)
Rate controlling step is polymer erosion

n = 0.5 - Fickian diffusion is the rate controlling mechanism (ficks law)

n = 0.5 - 1 - Both diffusion & polymer erosion control release kinetics