drug receptor interactions Flashcards

1
Q

which form of the drug is more water soluble?

A

dissociated unprotonated form

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2
Q

which form of the drug is more lipid soluble?

A

undissociated protonated form

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3
Q

how do you calculate volume of distribution?

A

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

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4
Q

what does Vd show?

A

how well a drug is distributed around the body

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5
Q

what does a high Vd indicate?

A

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

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6
Q

what does a low Vd show?

A

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

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7
Q

what is drug distribution?

A

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

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8
Q

what are the major body compartments?

A

water
fat
solid

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9
Q

what is the water compartment made up of?

A

ICF

ECF (plasma and ISF)

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10
Q

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

A

60%

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11
Q

what does the fat compartment consist of?

A

brain
adipose tissue
cell membranes

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12
Q

what does the solid compartment consist of?

A

bone

muscle

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13
Q

what is albumin?

A

a plasma protein that drugs can bind to

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14
Q

how does albumin help in the transport of drugs?

A

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

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15
Q

in what form can drugs bind to receptor?

A

in the free form

not bound to proteins

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16
Q

what determines efficacy?

A

free drug concentration around target tissue

17
Q

when is a drug considered active?

A

when its free

18
Q

when is a drug considered inactive?

A

when it’s bound to a plasma protein

19
Q

what conditions affect the level of plasma proteins?

A

liver disease

20
Q

what is warfarin?

A

anticoagulant

21
Q

what is phenytoin?

A

anti-seizure medication

22
Q

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

A

bulk flow
passive diffusion
active transport

23
Q

what does the effect of a free drug depend on?

A

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

24
Q

explain how capillary structure affects the movement of free drugs?

A

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

25
Q

how do hydrophobic drugs get to the blood?

A

across biological membranes

26
Q

how do hydrophillic drugs get to the blood?

A

through junctions of endothelial cells in capillary eds

27
Q

how do small drugs get out of a blood vessel?

A

free diffusion

28
Q

why cant polar drugs enter the CNS?

A

unable to enter the endothelial cells

29
Q

what happens in ion channels?

A

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

30
Q

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

A

sodium

neuronal excitation

31
Q

how does glutamate work and what does it do?

A

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

32
Q

how does GABA work and what does it do?

A

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

33
Q

explain how receptor tyrosine kinases work

A
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
34
Q

explain how nuclear receptors work

A

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

35
Q

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

A

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

36
Q

what is tachyphylaxis?

A

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

37
Q

describe the mechanism for tachyphylaxis

A

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

38
Q

what drugs commonly cause tachyphylaxis?

A

drugs that affect the CNS

39
Q

give an example of tachyphylaxis

A

salbutamol