drug receptor interactions

Question 1

which form of the drug is more water soluble?

Answer 1

dissociated unprotonated form

Question 2

which form of the drug is more lipid soluble?

Answer 2

undissociated protonated form

Question 3

how do you calculate volume of distribution?

Answer 3

amount of drug in the body divided by the plasma concentration of the drug

Question 4

what does Vd show?

Answer 4

how well a drug is distributed around the body

Question 5

what does a high Vd indicate?

Answer 5

small concentration in the blood. more is in the tissue. drug is more lipid soluble

Question 6

what does a low Vd show?

Answer 6

high concentration in the blood. more is in the plasma. more water soluble.

Question 7

what is drug distribution?

Answer 7

process by which drug reversibly leaves the blood stream and enters the extra cellular fluid

Question 8

what are the major body compartments?

Answer 8

water
fat
solid

Question 9

what is the water compartment made up of?

Answer 9

ICF

ECF (plasma and ISF)

Question 10

what proportion of the body weight does the water compartment make up?

Answer 10

60%

Question 11

what does the fat compartment consist of?

Answer 11

brain
adipose tissue
cell membranes

Question 12

what does the solid compartment consist of?

Answer 12

bone

muscle

Question 13

what is albumin?

Answer 13

a plasma protein that drugs can bind to

Question 14

how does albumin help in the transport of drugs?

Answer 14

drugs bind to albumin once they’re released from the GI system and they’re carried in an inert form. protects drug from body’s metabolism

Question 15

in what form can drugs bind to receptor?

Answer 15

in the free form

not bound to proteins

Question 16

what determines efficacy?

Answer 16

free drug concentration around target tissue

Question 17

when is a drug considered active?

Answer 17

when its free

Question 18

when is a drug considered inactive?

Answer 18

when it’s bound to a plasma protein

Question 19

what conditions affect the level of plasma proteins?

Answer 19

liver disease

Question 20

what is warfarin?

Answer 20

anticoagulant

Question 21

what is phenytoin?

Answer 21

anti-seizure medication

Question 22

what methods can a drug use to get into the intracellular fluid?

Answer 22

bulk flow
passive diffusion
active transport

Question 23

what does the effect of a free drug depend on?

Answer 23

capillary structure
chemical nature of the drug
blood flow through the tissue
presence of non-active binding sites

Question 24

explain how capillary structure affects the movement of free drugs?

Answer 24

fenestrated capillaries means there are gaps in the BM so drugs can get through

continuous capillaries - thick BM so drug cant get through

intermittent capillaries = certain amount of movement

Question 25

how do hydrophobic drugs get to the blood?

Answer 25

across biological membranes

Question 26

how do hydrophillic drugs get to the blood?

Answer 26

through junctions of endothelial cells in capillary eds

Question 27

how do small drugs get out of a blood vessel?

Answer 27

free diffusion

Question 28

why cant polar drugs enter the CNS?

Answer 28

unable to enter the endothelial cells

Question 29

what happens in ion channels?

Answer 29

ligand binds and causes conformational change - ion channel opens. ions move down a concentration gradient

Question 30

what ions move through nicotinic receptors and what effect does this have?

Answer 30

sodium | neuronal excitation

Question 31

how does glutamate work and what does it do?

Answer 31

binds to calcium channels to cause neuronal excitation by causes a depolarisation

Question 32

how does GABA work and what does it do?

Answer 32

binds to Cl- channels and causes neuronal inhibition by hyperpolarising the cell

Question 33

explain how receptor tyrosine kinases work

Answer 33

``` ligand binds outside the cell causes inactive monomers to become phosphorylated dimers form the conversion of ATP to ADP activates receptor activates protein causes response ```

Question 34

explain how nuclear receptors work

Answer 34

lipophillic hormone crosses the cell membrane dimerises and crosses nuclear membrane binds to DNA activates transcription mRNA transcribed and becomes protein and changes the cell function

Question 35

list the receptors from fastest to slowest and state how long they take

Answer 35

Ligand gated - ms GPCR - seconds RTK - mins/hours nuclear receptors - hours

Question 36

what is tachyphylaxis?

Answer 36

acute and sudden decrease in response to a drug after its administration

Question 37

describe the mechanism for tachyphylaxis

Answer 37

1 - receptor desensitisation 2 - receptor internalisation 3 - physiological adaptation - side effects decline 4 - depletion of mediators e.g. signalling molecules 5 - increased metabolic degradation

Question 38

what drugs commonly cause tachyphylaxis?

Answer 38

drugs that affect the CNS

Question 39

give an example of tachyphylaxis

Answer 39

salbutamol