Oral transmucosal drug Delivery

Question 1

What is the pH of saliva and how does saliva affect oral transmucosal delivery

Answer 1

Around 6.4
It has water, proteins, enzymes that breakdown foods etc e.g amylase, lysozymes breakdown bacteria, - has high pH with increased secretions

Question 2

Why is the permeability of the oral transmucosal route better?

Answer 2

More hydrated than the Gut and rich blood supply

Question 3

What are the properties of the buccal route

Answer 3

Lower permeability 
Slower absorption 
Expanse of smooth muscle 
Immobile 
Thicker 500-800um

Question 4

What are the properties of the S/L route

Answer 4

Higher permeability
Faster absorption
Constantly washed by saliva . - short duration
Thinner 100-200um

Question 5

Which route is better for sustained release?

Answer 5

Buccal as it has lower permeability and slower absorption

Question 6

How does logP affect absorption through buccal mucosa?

Answer 6

Higher logP means less polar - so it is more soluble in lipids (less polar solvents) - so it can permeate better through the membranes and better absorb
(lower logP is more polar so cannot permeate through fatty membranes)

Question 7

How does charge/pH affect absorption through buccal mucosa?

Answer 7

increase permeability as less charged molecule.

LESS CHARGE = BETTER PERMEABILITY

Question 8

Chloroquine is a weak base - how can we ensure optimal absorption?

Answer 8

At low pH it is protonated (charged +ve ) as it is a base (ionised), so if we increase pH, it will cause it to deprotonate, less charge = aids absorption and permeability

Question 9

How can we ensure optimal absorption of a weak acid?

Answer 9

Weak acids at high pH are charged - deprotonates the nitrogen and causes a negative charge, so reduce the pH, to increase permeability

Question 10

What factors favour drug penetration in oral mucosal delivery?

Answer 10

1. Less polar - permeates better
2. Must be unionised at salivery pH 6.4 to permeate and not bind too strongly to oral mucosa
3. Low MWt - permeate better
4. Biphasic solubility to be soluble in aqueous salivery fluid and lipids
   - Dont want it to dissolve in saliva

Question 11

What are the 2 types of patches for buccal delivery

Answer 11

Multi-directional release - releases drug in all directions

Undirectional release patch - only attached to surface where 1 side releases drug and has impermeable backing.

Question 12

Disadvantaged of a multidirectional release patch

Answer 12

Drug diluted in saliva
Lose drug when saliva swallowed
Releases drug into mouth meaning not protected from physiological environment - amylases etc

Question 13

Disadvantages of an undirectional release patch

Answer 13

Available absorption area is quite small - so permeation will be slower
- Backing layer may decrease the film flexibility leading to discomfort

Question 14

What polymers are used for mucoadhesives in oral transmucosal delivery

Answer 14

Carbopol - weakly cross linked derivative of poly(acrylic acid)

• HPMC
• Cihitosan

Question 15

Advantage of oral transmucosal

Answer 15

fast onset of action 
Avoid GIT exposure of drugs 
Direct access to systemic circulation 
Rapid absorption 
Easy to administer and terminate

Question 16

Disadvantages of this route

Answer 16

Small absorptive surface area 
Less permeable than SI 
Saliva issues - dissolved in 
movement in mouth
have to try and avoid swallowing

Question 17

What are the requirements for mucoadhesive buccal films?

Answer 17

flexibility, elasticity, softness
Adequate strength to withstand mouth activity stress
good mucoadhesive ability to retain
swelling of films shouldnt be too intense to prevent discomfort

Question 18

Size and dose requirements of a buccal film

Answer 18

1-3 cm2

Daily dose of 25mgor less