Oral Drug Delivery 1

Question 1

Routes of drug administration (9)

Answer 1

1. Oral
2. Rectal
3. Vaginal
4. Nasal
5. Transdermal
6. Parenteral
7. Ocular
8. Pulmonary

Question 2

Types of oral dosage forms

Answer 2

SOLID: tablets & capsules (solid- & liquid- filled)
LIQUID: solution, emulsion, suspension, elixir, syrup

Question 3

Advantages of oral dosage forms (5)

Answer 3

1. Patient acceptability & compliance (more common & convenient)
2. Commercial advantages (cheaper than parenteral and other routes of delivery)
3. Relatively rapid absorption and onset of action (rich blood supply of GIT)
4. Prolonged retention possible (allow lowering of dosing frequency)
5. Large surface area for drug absorption

Question 4

Disadvantages of oral dosage forms (3)

Answer 4

1. Variability (irregular absorption)
2. Adverse reactions (locally irritating or sensitizing drugs that may cause damage to stomach mucosa)
3. Limited types of drugs that can be administered via oral route (due to high metabolic activity of GIT, extreme pH, intestinal motility, mucus barrier, impermeable epithelium)

Question 5

Disintegration

Answer 5

Process of breaking down a dosage form into smaller drug particles.

Question 6

Dissolution

Answer 6

Process by which smaller drug particles in the GI surface layer dissolves. This forms a saturated solution surrounding the drug particles. This acts as a diffusion layer before absorption.

Question 7

Rate-limiting step

Answer 7

It is the slowest step in a series of reactions, which controls the overall rate and extent of appearance of intact drug in the systemic circulation.

Question 8

How to overcome low solubility drugs?

Answer 8

1. Give at high doses
2. Take with a fatty meal (drugs are lipid soluble and can dissolve in fat)

Question 9

When does steady state occur?

Answer 9

When drug steadily dissolves in the solid-liquid interface and diffuses through the stagnant layer.

Question 10

What do each of the following letters in the noyes-whitney equation stand for?

DM/DT =
D =
A =
Cs =
C =
H =

Answer 10

DM/DT = Dissolution rate
D = Diffusion coefficient of drug in GIT fluid
A = Effective SA of drug particle in contact with GI fluid
Cs = Solubility of drug in diffusion layer
C = Concentration of drug in GI fluid at time T
H = Thickness of diffusion layer

Question 11

Describe the absorption process (DDDPDP)

Answer 11

1. Disintegration: depending on choice of excipients
2. Dissolution: in GI fluid
3. Diffusion: across stagnant diffusion layer surrounding drug particles to reach GI surface layer
4. Partition: from GI fluid into GI lipid bilayer
5. Diffusion: across GI lipid bilayer
6. Partition: from GI lipid bilayer into bloodstream

Question 12

Physiological factors affecting bioavailability (5)

Answer 12

1. Gastric transit: GER
2. GI pH
3. GI viscosity/composition
4. GI volume
5. Presence of GI enzymes

Question 13

What happens when tablet/capsules are lodged in the oesophagus? (5)

Answer 13

Partial dehydration + gel formation → Adhesion → Choking → Erosion of membrane lining → Ulceration

Question 14

Gastric Emptying Rate (GER)

Answer 14

Time taken for a dosage form to pass through the stomach

• Proportional to the volume of food left in the stomach
• Rate ↑, GER ↓
• Time ↑, GER ↑

Question 15

Factors that slow GER will (3)

Answer 15

1. Prolong onset for drug action
2. Reduce therapeutic efficacy of drug
3. Reduce bioavailability of drugs

Question 16

Factors that affect GER (5)

Answer 16

1. Patient’s emotional state
   (depression, ↓ GER)
2. pH of stomach contents
   (↓ pH, ↓ GER)
3. Intensity of activity
   (↑ intensity, ↓ GER)
4. Disease state
   (ulcers, ↓ GER)
5. Type of meal
   (carbohydrates, ↓ GER)
   (fat, ↑ GER)

Question 17

How does pH affect absorption? (3)

Answer 17

1. Chemical stability
2. Ionisation
3. Dissolution rate/solubility