Module 2G Rectal Drug Delivery

Question 0

Discuss the advantages and disadvantages of rectal drug delivery over oral systems (12)

Answer 0

Advantages:

1. Improved enzymatic drug stability
2. Partial avoidance of hepatic first pass effect
3. Higher drug load
4. Lymphatic delivery
5. Constant and static environment
6. Patients with swallowing difficulty
7. Avoidance of overdosing

Disadvantages:

1. Patient acceptance and compliance
2. Potential for nonspecific drug loss (May be voided early)
3. Limited fluid in the rectum (limit dissolution of drugs)
4. Formulation
5. Expense

Question 1

Discuss the rational for selecting rectal drug administration (6)

Answer 1

1. Patient unable to take oral drugs
   
   • Problem with GI tract, nausea, unconscious
2. Drug is less suited for oral administration:
   
   • Oral route causes GI irritation or unacceptable taste
   • Drug is susceptible to pH, enzyme or liver metabolism
   • Drugs that are abused can be formulated into suppositories
3. A local effect is desired eg: haemorrhoids, laxatives

Question 2

Describe the formulation requirements for a suppository base (7)

Answer 2

Melt in body temperature or dissolve in rectal fluid
Volume contraction to permit removal from mould
Viscosity
Stable
Comparable with drug

Question 3

Describe the different types of suppository bases available (4)

Answer 3

Fatty vehicles:
- Almost exclusively semi or fully synthetic
Eg: PCCA base MPK fatty acid base
Water soluble vehicles:
- hydroscopic therefore attract water, resulting in a painful
sensation for the patient. To reduce this moisten before insertion
Eg: PCCA poly glycol base