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Clinical > drug routes (pharmacology 2 bds2) > Flashcards

drug routes (pharmacology 2 bds2) Flashcards

1
Q

what are the routes of drug administration

A

enteral or parenteral ( ie via the gut or not via the gut) with subcategories

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2
Q

what is first pass metabolism

A
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3
Q

how is a drug transported in the blood

A
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4
Q

describe the stages of drug metabolism

A
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5
Q

what are the routes of excretion for drugs

A
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6
Q

what are the steps the drug takes from administration to excretion

A

administration
absorption
transport
clinical effect
metabolism
excretion

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7
Q

what are the routes of administration classified as enteral

A

this means via the gut and include
- oral
- rectl
- nasogastric
- nasointestinal
- PEG

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8
Q

what are the routes of administration under the parenteral classification

A

this means not via the gut and includes
- transdermal
- transmucosal
- intravenous
- intramuscular
- subcutaneous
- inhalation

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9
Q

what are the advantages of oral route drug administration

A

convenient
portable
painless
non invasive
cost effective
patient can self administer

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10
Q

what are the disadvantages of oral route drug administration

A

slow onset
may be inefficient
variable absorption
first pass metabolism

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11
Q

what is first pass metabolism

A

drugs entered via the gut can only enter circulation after passing through the liver, where it is metabolised. this means a portion of the drug can either be inactivated or activated, which is something that varies with liver disease and age.

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12
Q

what happens if the liver inactivates the drug via first pass metabolism

A

means that more will be needed by oral route to get the desired clinical effect

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13
Q

what happens if a drug is activated by the liver

A

less will be needed to be taken via the oral route if the liver can make an active form from an inactive drug

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14
Q

what are the advantages of intravenous// intramuscular drug administration

A

very rapid onset, predictable plasma levels and there is no first pass metabolism. this is because the drug is administered straight to the muscle or to circulation and will not have to pass through the liver first

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15
Q

what are the disadvantages of intravenous/ intramuscular drug administration

A

allergic reactions are more severe and the action duration is shorter
trained staff will have to administer it, it is more painful and the cost of the drug is higher

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16
Q

how does transdermal and subcutaneous drug administration work

A

this is when the drug is absorbed through the skin into the bloodstream and is usually just patches on the skin

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17
Q

what are the advantages of transdermal and subcutaneous drug administration

A

there is no first pass metabolism
allergic reactions can be very localised
action is prolonged, can stretch over days with patches
can be self administered

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18
Q

what are the disadvantages of transdermal and subcutaneous drug administration

A

the onset is very slow and the drugs cost is higher
the effect varies from person to person and from site to site

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19
Q

what is drug bioavailability

A

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

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20
Q

how can bioavailability of drugs be modified

A

pharmaceutical factors: dosage, formulation, route of administration

physiological factors: destruction in the gut, poor absorption, first pass metabolism

21
Q

what is drug distribution

A

this is the movement of a drug to and from the blood and various tissues

22
Q

describe the route of drug distribution

A
  • drug is dissolved in the blood and transported bound to carriers
  • carries are usually plasma proteins like albumin
  • bound drug is inactive but competitive binding could lead to drug interactions
23
Q

which factors can impact the speed of diffusion into tissues from the blood

A
  • blood flow to the area
  • membrane characteristics
  • pH
  • active secretion of the drug into the tissue
24
Q

what is planning drug use based on the idea of

A

body compartment model

25
Q

describe the single compartment model for planning drug use

A

this is when the drug behaves as if it is evenly distributed throughout the body
body described as a single uniform compartment and there is rapid and homogenous distribution of the drug

26
Q

describe the two compartment model for planning drug use

A

this is when the drug behaves as if it is in equilibrium with different tissues in the body
central and peripheral compartment - central is the highly perfused tissues with rapid drug distribution and the peripheral compartment has slower distribution because the tissues are not as well perfused

27
Q

explain volume of distribution

A

different parts of the body receive different drug levels compared with plasma (relate to the compartment model)

drug selection may depend upon the preference of some drugs for some areas of the body, and some drugs are actively secreted into tissues or fluid rather than just simple diffusion

volume of distribution reflects the relationship between the amount of drugs in the body and plasma drug concentration. it is the apparent volume at which the current amount of drug in the body must be dispersed in order to give the current drug concentration and does not actually represent a physiological volume

28
Q

advantage of drugs with lipid binding in tissues

A

slow release from accumulation gives the drug a more prolonged effect

29
Q

describe how drugs are prepared for elimination from the body

A

phase 1 reactions are modification, including oxidation reduction and hydrolysis

phase 2 reaction are conjugation, ie when a compound is formed from combining two or more substances, including glycuronidation, sulphating, methylation and acetylation

30
Q

what is the name for the super family of enzymes found mainly in the liver involved in the metabolism of drugs through a series of oxidation and reduction reactions

A

cytochrome p450 mono-oxygenate system

31
Q

why is the basis for drug testing in the police usually some form of body fluid

A

this is how drugs are excreted from the body

32
Q

what does the most extensive secretion if drugs occur through

A

renal excretion of water soluble metabolites via urine

liver metabolism and excretion via bile

lungs via inhaled gases and volatile fractions of other drugs

33
Q

what are the drugs related to plasma concentration excreted through

A

sweat
saliva
tears

34
Q

what are the three stages to drug elimination through the kidneys

A

glomerular filtration
reabsorption
secretion

35
Q

how can renal disease interfere with drug excretion

A

chronic renal failure meaning filtration of blood is not efficient
in these cases the drug doses must be reduced

36
Q

how can liver disease interfere with drug excretion

A

liver failure resulting in improper metabolism of drugs, again the drug doses must be reduced

37
Q

when reducing drug use in an individual case of renal or liver disease, which factors can impact how much the drugs are reduced

A

depending on the organ function and which drug is being used

38
Q

what is the plasma half life of a drug

A

this is the time taken to eliminate half of the drug

39
Q

describe first order kinetics in relation to drugs

A

drug elimination increases as the drug concentration increases, excretion is through passive diffusion

40
Q

describe zero order kinetics in relation to drugs

A

drug elimination is at a fixed rate, and is an active process irrespective of drug concentration. there can be drug accumulation if the saturation is exceeded

41
Q
A

first order kinetics

42
Q
A

first order kinetics

43
Q
A

zero order kinetics

44
Q
A

zero order kinetics

45
Q

describe elimination of blood alcohol

A

zero order process where alcohol is removed from the body at a constant rate independent of its concentration, but this relationship does not exist at a lower blood alcohol concentration and will switch to a first order process

46
Q

what happens if drug dosing is too frequent

A

plasma levels that may be toxic, depending on the drugs therapeutic index

47
Q

what happens if drug dosing is too infrequent

A

will result in sub therapeutic plasma levels and no clinical effect

48
Q

summarise paracetamol overdose

A
  • manufacturer recommended safe dose of 4g over 24 hour period
  • toxicology of these drugs arises from metabolic processes
  • metabolism occurs mainly in the liver
  • formation of toxic metabolites can cause liver damage, acute hepatotoxicity and liver failure
49
Q

which route of drug absorption is the least reliable

A

oral route

Clinical (27 decks)

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