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RAD 415 > pharmacology for medical imaging > Flashcards

pharmacology for medical imaging Flashcards

1
Q

what is pharmacology

A

the study of the actions, mechanism, uses and adverse effects of drugs

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2
Q

what is a drug

A

natural/semi-synthetic or synthetic substance that alters the physiological state of a living organism/system

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3
Q

what 2 disciplines is pharmacology divided into

A

pharmacodynamics
pharmacokinetics

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4
Q

what are the 7 ways drugs are classified (named)

A
  1. chemical structure
  2. source
  3. target organ/site of action
  4. mode of action
  5. therapeutic uses
  6. physiological system
  7. physical effects
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5
Q

what are the 3 types of names a drug has

A

chemical e.g hydroxyphenyl acetamide
non-proprietary (generic) e.g paracetamol
proprietary (brand) panadol

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6
Q

define pharmacodynamics

A

discipline studying the effects of a drug on various systems in the body

(looks at how drug binds to target site and initiates change)

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7
Q

what are 3 characteristics of a drug as they bind to receptors to initiate change

A

agonist
partial agonist
antagonist (competitive or non-competitive)

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8
Q

explain the what agonist partial agonist and antagonist characteristics of drugs are

A

agonist = fully activates the receptor

partial agonist = partial activates the receptor (not to maximum) (despite agonist being present, so long as the partial agonist is bonded, the receptor can only be partially activated)

antagonist = causes no action of receptor when bonded but if agonist and partial agonist is present, it prevents them from activating the receptor (as it is bonded)

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9
Q

define pharmacokinetics

A

fundamental scientific discipline that underpins the administration of drugs

(follows drug from moment its administered to when its eliminated from body)

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10
Q

Pharmacokinetics = what body does to drug
pharmacodynamics = what drug does to body

A
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11
Q

what are the 4 principles/processes of pharmacokinetics

A
  1. absorption
  2. distribution (drug spreads thru body)
  3. metabolism (process of body converting drug into metabolites being easy to eliminate)
  4. elimination (drug eliminated from body)
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12
Q

what is mean by absorption in PK

A

amount of drug in general circulation

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13
Q

what is bioavailability and how is it calculated

A

fraction of drug available to produce effect
F = (amount of drug in general circulation / amount of drug administered)

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14
Q

what are 3 concepts related to PK

A
  1. drug transfer
  2. drug properties
  3. effect of pH
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15
Q

what is drug transfer

A

drug must cross several barriers to be absorbed, distributed and eliminated from body

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16
Q

what are the 3 mechanisms of drug trasnfer

A

passive diffusion
active transport
facilitated transport

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17
Q

what are characteristics of drug properties

A

drug formulations e.g solid, liquid, polymer
drug chemistry e.g molecular shape/size, state of ionisation

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18
Q

what is water partition coefficient

A

a measure of the relationship between lipophilicity (fat solubility) and hydrophilicity (water solubility) of a substance.

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19
Q

what are most drugs in term of the pH scale

A

most drugs are weak acids or bases
in solution they present as a mix of ionised and nonionised forms

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20
Q

what are 2 things the degree of dissociation (of drugs in solution) dependant on

A
  1. pH of solution
  2. pKa of drug (dissociation constant)
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21
Q

whats the Henderson-hasselback equation

A

equation used to determine pH of a buffer

22
Q

how do ionised drugs affect dosage

A

ionised drugs become trapped in certain area and cant diffuse anymore thus reducing amount of drug available to produce an effect

23
Q

different routes of administration can maximise drug bioavailability

A
24
Q

what 2 things can differ due to change in bioavailability

A
  • loss of drug effectiveness
  • drug toxicity
25
Q

give examples of the different routes of administratin

A

oral
rectal
buccal

26
Q

which form of administration gives 100% bioavailability

A

intravenous

27
Q

what is used as an index of drug concentration in tissue

A

plasma concentration

28
Q

what 2 things are considered in distribution

A

1.initial drug distribution, depending on regional blood flow

  1. drug redistribution, depending on drug affinity for a particular tissue
29
Q

what is the volume of distribution

A

theoretical volume (in L) into which a drug dissolved to produce the plasma concentration observed at steady state

30
Q

what is the equation for volume of distribution

A

Vd = (amount of drug given / steady state plasma concentration )

31
Q

what is the clinical importance of volume of distribution

A

changes in Vd influence plasma concentration of drug and dose may need adjusting

32
Q

where is the major site of metabolism

A

liver
(can occur in kidney, lungs, gut)

33
Q

what type of molecules can be eliminated from body

A

only water soluble molecules

34
Q

most drugs are lipophilic (lipid soluble)

A
35
Q

what is the clinical importance of metabolism

A
  • converts drugs to inactive metabolites
  • converts drugs to active metabolites
  • convertes inactive metabolites to active metabolites
  • converts drugs to toxic molecules
36
Q

what 4 things influence metabolism

A
  • interaction with other drugs
  • ageing
  • disease (live disease mainly)
  • genetic polymorphism (presence of two or more variant forms of a specific DNA sequence)
37
Q

what are the 5 routes of elimination

A

renal
pulmonary
biliary
sweat, tears
breast milk

38
Q

what is the clinical importance of drug excretion/elimination

A

changes in elimination will trigger changes in drug administration

39
Q

generally only hydrophilic molecules can be excreted

A
40
Q

what 2 types of time dependant patterns does drug elimination occur at

A

1st and zero order kinetics

41
Q

what is zero order kinetic pattern

A

-constant amount of drug eliminated per unit time
- rate of drug elimination independent of drug plasma concentration

42
Q

what is 1st order kinetics

A
  • constant fraction of drug eliminated per unit time
  • rate of drug elimination proportional to drug plasma concentration
43
Q

clinical importance of 1st order kinetics

A
  • time to eliminate drug is INDEPENDENT of dose
  • increasing dose/frequency of administration produces PREDICTABLE rises in plasma conc
  • most drugs use 1st order kinetics
44
Q

clinical importance of 0 order kinetics

A
  • time to eliminate drug DEPENDENT of dose
  • increasing dose/frequency of administration produces UNPREDICTABLE rises in plasma conc
  • makes drug administration complicated
45
Q

what is the elimination rate constant

A

describes the fraction of drug eliminated per unit time

46
Q

what is half life

A

interval of time to reduce the plasma concentration by half

47
Q

HALF LIFE IS INDEPENDENT OF DOSE

A
48
Q

What is half life parameter useful to estimatet

A
  • time to clear drug from body
  • duration of action
  • time to achieve steady state
  • dosage interval to maintain steady state
49
Q

what 4 types of contrast media is used in PK

A

iodine based
barium based
gadolinium based
saline and gas

50
Q

what are some adverse drug reactions found in pharmacology

A
  • reactions to contrast media alone
  • interactions with drugs
51
Q

what are some forms of drug and contrast media interactions

A
  1. reduced feral function with reduced drug excretion e.g metformin
  2. enhanced contrast medial renal effects e.g diuretics
    3.enhanced allergic-like reactions to contrast media e.g alpha receptor blockers
  3. enhanced contrast media cardiac effects e.g calcium blockers
  4. interference with haematological effects of contrast media (coagulation and fibrinolysis) e.g anticoagulants
  5. contrast media and neuroleptic drugs e.g antidepressants
52
Q
A

RAD 415 (19 decks)

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