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My1 Principles > Pharmacology - drug ADME > Flashcards

Pharmacology - drug ADME Flashcards

1
Q

what is pharmacodynamics

A

what a drug does to the body

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2
Q

what is pharmacokinetics

A

what body does to a drug eg absorption, distribution, metabolism

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3
Q

what is medicine

A

a combo of drugs and other substances for healing

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4
Q

what are receptors

A

macromolecules on/ in cells that mediate hormones

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5
Q

what is an agonist

A

binds to receptor and produces cellular response

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6
Q

what is an antagonist

A

reduces/ blocks the actions of an agonist by binding to same receptor

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7
Q

what is affinity

A

the strength of bond between receptor and agonist (slow dissociation rate = high affinity_

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8
Q

what is efficacy

A

ability to evoke a cellular response

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9
Q

what do antagonists have

A

affinity but not efficacy

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10
Q

what is EC50

A

agonist % when the response is half of it’s maximum

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11
Q

what is potency

A

lower conc = higher potency. less needed to do the job

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12
Q

in competitive agonists and antagonists, what does this have on EC50

A

shifts curve to right, more is needed to get response

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13
Q

in non-competitive antagonists what effect is there on EC50 if you increase conc

A

none, cannot increase active receptors

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14
Q

what is absorption

A

process by which a drug enters the body from it’s site of administration

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15
Q

what is distribution

A

process by which drugs enter blood and tissues

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16
Q

what is metabolism

A

conversion of drug to less active form

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17
Q

what is excretion

A

process which removed drug from body

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18
Q

what factors affect absorption (4)

A

solubility, stability (not destroyed in acid stomach), lipid to water partition coefficient (lipid soluble), degree of ionisation (unionised)

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19
Q

when pKa = pH what does this mean for the drug

A

it is 50% ionised 50% not

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20
Q

what is the equation for week acids

A

pH = pKa + log ([A-]/[AH])

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21
Q

what is better absorbed weak or strong acids and bases

A

weak

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22
Q

where are weak acids normally absorbed

A

stomach lumen

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23
Q

where are weak bases normally absorbed

A

small intestine

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24
Q

what is oral availability

A

fraction of drug that enters blood stream after ingestion

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25
Q

what is systemic availability

A

fraction that enters systemic circulation after absorption

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26
Q

what are some enteral drug routes

A

oral, sublingual, rectal

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27
Q

what are some parenteral drug routes

A

IV, IM, topical, inhalation

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28
Q

which drugs are more able to move around water compartments by diffusion

A

unionised

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29
Q

what is volume distribution (Vd)

A

volume in which a drug is dissolved (dose/ plasma conc)

30
Q

a Vd of less than 10 indicates the drug is where

A

vascular compartment

31
Q

a Vd of 10-30 means what

A

drug is in extracellular compartment

32
Q

Vd of more than 30 indicates what

A

drug is in total body water

33
Q

what is the MEC

A

minimum effective concentration

34
Q

what is the MTC

A

maximum tolerated concentration

35
Q

what is the therapeutic ratio

A

MTC/MEC, safe drugs have a high ratio, unsafe have a low ratio

36
Q

why does a low MTC/MEC mean a drug is unsafe

A

because there is a risk of poisoning the patient

37
Q

how is the initial concentration for a drug determined (Co)

A

D/Vd

mass / volume of blood

38
Q

what to later concentrations depend on

A

elimination rate constant (Ke)

39
Q

what is Ke

A

elimination rate constant, the fraction of a drug eliminated per unit time

40
Q

what is first order kinetics

A

rate of elimination is proportional to drug conc (half life)

41
Q

what is this half life

A

the time it takes for a drugs conc to half

42
Q

what is the equation for t1/2

A

0.693/Kel

43
Q

does first order kinetics change half life or Ke of a drug

A

no and no

44
Q

what is clearance (CL)

A

volume of plasma cleared of a drug per unit time (norm = L/hr)

45
Q

what is Cp

A

plasma absorption

46
Q

what is the equation for the rate of elimination

A

CL x Cp

47
Q

what is steady state

A

rate of drug admin = rate of drug elim

48
Q

what is Css

A

steady state concentration of a drug

49
Q

after how many half lives is Css normally achieved

A

5

50
Q

in oral dosing what should plasma conc fluctuate around

A

average steady state value

51
Q

what is a loading dose

A

an originally higher dose given at the beginning of a course to increase time to reach steady state for drugs with long half life

52
Q

what is zero order kinetics

A

drugs eliminated at a constant rate, changes to first at low concs

53
Q

what are drugs (x..)

A

xenobiotics, foreign chemicals

54
Q

what does metabolism do

A

coverts parent drugs to more polar metabolites that are not as readily absorbed in renal tubules and so excreted

55
Q

what organ carries out most drug metabolism

A

liver

56
Q

what are the 2 faces of drug metabolism

A 
1 = oxidation, reduction, hydrolysis
2 = conjunction
57
Q

where does phase 1 occur

A

Right hand side of liver

58
Q

where does phase 2 occur

A

left hand side of liver

59
Q

what is the purpose of phase 1

A

makes it more polar (ionised) by adding a reactive group

60
Q

what is the purpose of phase 2

A

adds an endogenous compound (carbon) to increase polarity

61
Q

what do CYP450 proteins do

A

haem proteins that oxidate drugs in phase 1 by monooxygenase cycle

62
Q

what is a common phase 2 reaction and what enzyme carries it out

A

glucuronidation, UDP-glucuronyl transferase

63
Q

what are the major organs involved in drug excretion

A

kidneys

64
Q

what are the 3 main processes involved in excretion

A

glomerular filtration, active tubular secretion and passive reabsorption by diffusion

65
Q

drugs must be in what state to enter filtration via glomerular filtration

A

unbound

66
Q

a drugs molecular weight (MW) must be under what to be excreted via glomerular filtration

A

less than 20,000

67
Q

in tubular excretion, what 2 transporter systems actively secrete drugs into nephron lumen

A

organic anion transporter (OAT - acidic drugs) and organic cation transporter (OCT - basic drugs)

68
Q

why is tubular excretion potentially the most effective (3)

A

1) max clearance even in bound proteins (to plasma), 2) can concentrate drugs against electrochemical gradient 3)each transporter has maximum Tm for drug

69
Q

what is passive reabsorption

A

concentration of urine favours passive reabsorption across distal tubule by diffusion

70
Q

what factors affect rate of reabsorption

A

lipid solubility, polarity, urine flow rate, urine pH

My1 Principles (12 decks)

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