Pharmacokinetics- absorption/ distribution

Question 1

What is pharmacokinetics?

Answer 1

how a drug is absorbed, metabolised and removed form the body

Question 2

What are enteral administration routes? name some

Answer 2

delivery to internal environment through the gi tract
oral
sublingual
rectal

Question 3

Name some advantages of oral administration

Answer 3

self administration
convenient
non invasive
systemic

Question 4

Name some disadvantages of oral administration

Answer 4

taste
poor absorption
first pass metabolism

Question 5

What are parenteral route? name some

Answer 5

delivery via all other routes that are not the GI tract 
intravenous 
intrathecal 
intramuscular 
inhalation 
topical application

Question 6

Name some advantages of intramuscular administration

Answer 6

faster than oral

Question 7

Name some disadvantages of intramuscular administration

Answer 7

absorption dependent localisation and blood flow
limited injection volume
painful

Question 8

Name some advantages of intravenous administration

Answer 8

fast direct

can control rate of delivery

Question 9

Name some disadvantages of intrathecal administration

Answer 9

painful

risk of spinal injury

Question 10

Name some advantages of inhalation administration

Answer 10

direct absorption and elimination via lungs

allows rapid adjustment of plasma concentration

Question 11

What features of the si allow efficient absorption

Answer 11

surface area large

movement of material present drugs molecules continuously to gi tract epithelia

Question 12

Name the main route of absorption

Answer 12

passive diffusion
facilitated diffusion
secondary active transport

Question 13

What features affect passive diffusion

Answer 13

lipophilic

ionisation state

Question 14

What features affect facilitated diffusion

Answer 14

SLC availability

Question 15

What features affect secondary facilitated diffusion

Answer 15

SLC availability

existence of electrochemical gradient generated by another transporter using atp

Question 16

What is penicillin co transported with

Answer 16

h+ ions via secondary active transport using slc

Question 17

Name physiochemical factors affecting drug absorption

Answer 17

gi length/ sa
drug lipophilicity
density of slc expression

Question 18

Name gi physiology factors affecting drug absorption

Answer 18

motility
blood flow
food
pH

Question 19

explain first pass metabolism

Answer 19

gut some E denature drugs

gut and liver phase 1 cp450 and conjugate phase 2 enzymes may metabolise drugs so they do not enter circulation

Question 20

define bio availability

Answer 20

fraction of a defined dose which reaches its way into a specific body compartment
cvs/ circulation usually the reference

Question 21

What does bio availability (f) allow comparison of how is his comparison made ?

Answer 21

compare routes of drug administration
look at area under time vs plasma concentration curve
IV = 100% therefore f=1 as all reaches systemic circulation
other routes f= <1

Question 22

Describe drug distribution

Answer 22

bulk flow arteries to capillaries

diffusion capillaries to interstitial to intracellular

Question 23

name some barriers to diffusion

Answer 23

capillary permeability dependent on type
slcs
drug pka. local ph (ion trapping)
binding of drug to plasma or tissue proteins reduced free drug

Question 24

What are the three compartments in the simplified model?

Answer 24

plasma
interstitial fluid
intracellular

Question 25

What is Vd?

Answer 25

volume of fluid required to contain the total amount of drug in the body at the same concentration as that present in the plasma
it is a proportionality constant that relates plasma concentration to the amount of drug in the body
only provided indication of the distribution of the drug within the body

Question 26

what does decrease vd mean?

Answer 26

decrease penetration into interstitial/ intracellular compartments

Question 27

What does increase vd mean?

Answer 27

increase penetration into interstitial/ intracellular compartments

Question 28

how is vd calculated?

Answer 28

drug does/ plasma conc t=0

Question 29

What is vd affected by?

Answer 29

normal push/ pull factors 
change in blood flow 
hypoalbuminiea 
body weight 
drug interaction 
renal failure 
pregnancy 
neonates 
geriatrics 
cancer patients 
anaesthetics

Question 30

where do acidic drugs accumulate and why?

Answer 30

high pH compartments

ion trapping

Question 31

where do basic drugs accumulate and why?

Answer 31

low pH compartments

ion trapping

Question 32

explain ion trapping

Answer 32

drug may move from one compartment to another in unionised form
change in compartment may be change in pH therefore becomes ionised
this prevents drug moving out of the compartment it is in and it accumulates