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BDS2 BAMS Pharmacology > Pharmacokinetics and pharmacodynamics > Flashcards

Pharmacokinetics and pharmacodynamics Flashcards

1
Q

what is pharmacodynamics

A

branch of pharmacology concerned with the effects of drugs and the mechanism of their action

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2
Q

what is pharmacokinetics

A

branch of pharmacology concerned with the movement of the drug within the body

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3
Q

what are the 4 phases to drugs

A

Absorption
Clinical effect
Metabolism
Excretion

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4
Q

what are the different ways to administer drugs

A 
oral
intravenous
intramuscular 
subcutaneous
inhalation
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5
Q

what are the advantages to oral administration

A

socially acceptable

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6
Q

what are the disadvantages to oral administration

A

slow onset
variable absorption
gastric acid may destroy drug

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7
Q

what do we mean when we say there is variable absorption of oral administered drugs

A

we do not know how much of the drug is going to be absorbed as there are so many variables that affect the absorption

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8
Q

what are other factors that affect oral absorption of drugs

A 
lipid solubility and ionisation
drug formulation
gastrointestinal motility
interactions with other substances
gi tract disease
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9
Q

how does lipid solubility and ionization affect the absorption of an orally administered drug

A

we can only absorb it if it is lipid soluble as because the cell membrane is lipid, lipid soluble drugs diffuse most rapidly. We can only hold the drug in the gut if it is not in ionic suspension

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10
Q

how does GI tract disease affect the absorption of an orally administered drug

A

if the gut is static for a while you will not move solutions through so you cannot move the drug to where it needs to be absorbed

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11
Q

what is first pass metabolism

A

blood of the gut is drained by hepatic portal vein and takes it to the liver

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12
Q

what happens in first pass metabolism

A

drug goes through hepatocytes and must be metabolized before going through circulation meaning that we will lose some of the drug in the liver

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13
Q

why do drugs that are absorbed through the mouth or top of the oesophagus have a quicker effect

A

do not go through HPV

bypass first pass metabolism

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14
Q

what veins do not drain into the hepatic portal veins

A

sublingual and rectal

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15
Q

when the drug goes through the liver it can have 1 of 2 effects, what are they

A

inactivate drug

activate drug

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16
Q

what does inactivation of drug by the liver mean

A

more is needed by oral route to get the desired clinical effect

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17
Q

what does activation of the drug by liver mean

A

makes an active form from an inactive drug

less is needed by oral route

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18
Q

what is an example of a drug that the liver inactivates during FPM

A

glyceryl trinitrate

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19
Q

what is an example of a drug that the liver activates during FPM

A

aciclovir

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20
Q

why is it important to know if a patient has abnormal liver function in respect to first pass metabolism

A

If the patient has abnormal liver function then there is a problem as the patient may not lose as much of the drug to first pass metabolism

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21
Q

when is abnormal liver function most common

A
  • Extremes of life
  • Liver disease
  • Drug interactions changing drug metabolism
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22
Q

what are the advantages to non-oral administration

A
  • It has predictable plasma levels
  • No first pass metabolism – injections bypass first pass metabolism and it means you know the drug is where it needs to be and you know it is working know and you know its dose
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23
Q

what are the disadvantages to non-oral administration

A

allergic reactions are more severe
access difficulity
cost is higher

24
Q

what is bioavailability

A

Bioavailability is the proportion of an ingested drug that is available for clinical effect

25
why can the bioavailability of oral drugs be low
variables may change the bioavailability of medicine and it changes day to day depending on what is happening inside the body
26
what is bioavailability modified by
* Dosage form * Destruction in the gut * Poor absorption * First pass metabolism
27
what is volume of distribution
Defined as the arrangement or rate of incidence of a drug in the body in relation to the measured plasma concentration Depends on blood flow to the different compartments and the ease of drugs going from the blood to the circulation
28
describe how we carry more drugs in the circulation than we can dissolve
can bind to lipids | can bind to plasma proteins
29
describe how drugs can bind to lipids
they are bound to lipids in the plasma and there is a slow release from accumulation
30
describe how drugs bind to plasma proteins
o The bound drug is inactive o This can act as a reservoir – the drug in the plasma will move into the tissues and then the drug in the plasma proteins will move into the plasma creating a reservoir
31
how can drug binding to plasma proteins be effected by competitive binding
different things bind to the same protein and this can change the way that drugs work
32
describe drug metabolism
prepare the drug for elimination from the body
33
describe phase 1 of drug metabolism
inactivate the medicine oxidation reduction hydrolysis
34
describe phase 2 of drug metabolism
``` get drug out of the body glucoronidation sulphation methylation acetylation glutathione ```
35
what is p450 monoxygenase system
variety of changes happen to the drug for excretion | the metabolism process can be interfered
36
what are the different ways the drugs can be excreted
``` Renal – urine Liver – bile Lungs – exhale gas sweat saliva ```
37
what is renal excretion
The kidney has a complex mechanism where it modifies the urine – the urine solution in the glomerulus mimics the amount in plasma. It changes in tubules as they add more drug or leave the drug
38
why is renal disease significant
impacts the ability to get rid of the drug and the drug can build up in circulation
39
what can changing pH of urine do
enhance excretion of acidic compounds and can help get rid of excess drug
40
what are disorders of excretion
``` Renal disease (chronic renal failure) Liver disease (liver failure) means that drug doses must be reduced ```
41
what is planning drug use based on
idea of body compartments
42
what are the 2 compartment models
single compartment model | two compartment model
43
what is the single compartment mode
the drug behaves as if it is evenly distributed throughout the body
44
what is the two compartment model
drug behaves as if it is in equilibrium with different tissues in the body
45
what is the plasma half life of a drug
Period of time required for the concentration of a drug in the body to be reduced by one half. We usually consider the half life of a drug in relation to the amount of drug in plasma – its half life depends on its clearance
46
what are the two ways drugs can be cleared
first order kinetics | zero order kinetics
47
describe first order kinetics
Drug elimination or absorption is by passive diffusion only – the drug goes into circulation and is removed from the body at a rate proportional to the concentration of a drug
48
what is the logarithmic graph of elimination by first order kinetics like
straight line | half life is constant
49
what is zero order kinetics
* Drug elimination is an active process and can be saturated by high concentrations * You can only remove a certain amount of a drug per hour
50
what is the graph of first order kinetics like
linear
51
what drugs use zero order kinetics
alcohol | paracetamol
52
what is drug accumulation
how the plasma concentration builds if repeated doses of a drug are given
53
what happens if the dosing schedule is too frequent
result in plasma levels that may be toxic | depends on the drug therapeutic index
54
what happens if the dosing schedule is too infrequent
result in sub-therapeutic plasma levels and no clinical effect
55
What do you need to know to calculate the dosing schedule
HALF LIFE, how its eliminated and how it accumulates

BDS2 BAMS Pharmacology (4 decks)

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