Absorption

Question 1

What is absorption?

Answer 1

Movement of drug into the blood stream

Question 2

What effects absorption (2)

Answer 2

1.Route of administration
2. Permeation - how many barriers to cross

Question 3

Give 4 features of oral administration

Answer 3

1. Convenient
2. Efficient
3. Uses pH differences in gut
4. Subject to first pass metabolism

Question 4

Give 3 features of buccal administration

Answer 4

1. Uses high blood flow
2. Avoids first pass metabolism
3. Works quickly

Question 5

Give 2 benefits of rectal administration

Answer 5

1. Avoids first pass metabolism
2. Non consistent absorption

Question 6

Benefits of inhalation (2)

Answer 6

1. Large surface area
2. High blood flow

Used volatile anaesthetics and asthma

Question 7

Benefits of topical (2)

Answer 7

1. Local effects
2. Low systemic effects but not none

Question 8

Transdermal - what to consider? (3)

Answer 8

1. Relies on lipid permeation
2. May cause irritation- bringing blood to surface
3. Don’t cut

Question 9

I/V vs I/M

Answer 9

1. IV quicker no absorption barrier
   2.IV 100% bioavailability
   3.IM depends on blood flow and perfusion of muscles

Question 10

What is bioavailability

Answer 10

Amount of drug that gets into circulation

• area under graph
• slope indicates administration

Question 11

Does bioavailability indicate effectiveness?

Answer 11

No

Question 12

What is bio equivalence ?

Answer 12

Therapeutic equivalency of 2 drugs ie generics

Some inequivalent so must prescribe brand eg lithium

Question 13

What effects absorption? (7)

Answer 13

1. Formulation
2. Dissolution of particles
3. Chem stability eg pH / enzymes
4. Gut motility
5. Food in gut
6. Passage across GI tract walls
7. Blood flow to GI tract

Question 14

What is drug half life t1/2

Answer 14

Time for concentration of drug in blood to fall by half

Question 15

How many half lives to get to steady state ?

Answer 15

5

Question 16

How can we speed up time to get to steady state?

Answer 16

Give loading dose

Question 17

What are the 4 main mechanics of drug permeation

Answer 17

1. Aqueous diffusion
2. Lipid diffusion ( most important- cell membrane has lipids)
3. Facilitated diffusion- carrier mol needs energy ATP
4. Pinocytosis - cell envelopes drug - bulky molecules eg proteins or hormones

Question 18

What does permeation depend on? ( 3)

Answer 18

1. Size of mol
2. Surface area
3. Concentration gradient