Module 2D Oral Trans-mucosal Drug Delivery

Question 0

Define: sublingual drug delivery

Answer 0

Absorption via mucosa under the tongue and floor of the mouth under the tongue. Eg: glycerol trinitrate spray, zofran wafers

Question 1

Define: membrane reservoir effect

Answer 1

The absorption of a drug from the mouth is not synonymous with drug entry into the systemic circulation. Instead the drug appears to be stored in the buccal membranes: the membrane reservoir effect.

Question 2

Define: buccal drug delivery

Answer 2

Absorption via the buccal mucosa lining the cheeks, gums and lips.

Question 3

Discus the regional differences in mucosal permeability in the oral cavity (4)

Answer 3

1. Keratin
   Hard palate and tongue = keratinised therefore, resistant to abrasion
   Cheek, floor of the mouth, soft palate = non-keratinised therefore,
   facilitates distensibility
2. Epithelial thickness
   Hard palate, floor of mouth = 100-120mm
   Buccal, lip mucosa = 500-600mm
3. Secretion of saliva
   Maintains a moist surface which enhances permeability
4. Presence of saliva
   Important in drug absorption for 2 main reasons:
   -Drug permeation across mucous membranes is fast
   -Faster absorption than a tablet

Question 4

What are the main advantages of the buccal route compared to peroral administration (3)

Answer 4

1. Bypasses acidic environment in the stomach
2. Faster therapeutic serum concentration of the drug
3. Bypasses first line metabolism by the liver

Question 5

Discuss advantages of oral trans mucosal (10)

Answer 5

1. Relatively large surface area (~100cm2)
2. Accessibility
3. Ease of use
4. Rich blood supply
5. Low metabolic activity
6. Low variability
7. Robust
8. Prolonged retention
9. Intestinal alternative
10. Zero order controlled release

Question 6

Discuss the disadvantages of the oral trans mucosal drug delivery (6)

Answer 6

1. Limited to potent molecules
2. Adverse reactions
3. Metabolic activity (don’t degrade drugs as well as GIT)
4. Mucus and salivary clearance (reduces retention time)
5. Mucous barrier (possible binding of drugs to mucous layer)
6. Patient acceptance (new therapy)

Question 7

Name 4 properties of a drug which affect its trans-mucosal permeability (4) (desired properties)

Answer 7

1. Molecular weight (low)
2. Ionisation (partitions easily and aqueous)
3. Water solubility in saliva (unionised at pH of 4)
4. Lipid solubility membrane penetration (unbound to oral mucosa)