drug routes (pharmacology 2 bds2)

Question 1

what are the routes of drug administration

Answer 1

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

Question 2

what is first pass metabolism

Question 3

how is a drug transported in the blood

Question 4

describe the stages of drug metabolism

Question 5

what are the routes of excretion for drugs

Question 6

what are the steps the drug takes from administration to excretion

Answer 6

administration
absorption
transport
clinical effect
metabolism
excretion

Question 7

what are the routes of administration classified as enteral

Answer 7

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

Question 8

what are the routes of administration under the parenteral classification

Answer 8

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

Question 9

what are the advantages of oral route drug administration

Answer 9

convenient
portable
painless
non invasive
cost effective
patient can self administer

Question 10

what are the disadvantages of oral route drug administration

Answer 10

slow onset
may be inefficient
variable absorption
first pass metabolism

Question 11

what is first pass metabolism

Answer 11

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.

Question 12

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

Answer 12

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

Question 13

what happens if a drug is activated by the liver

Answer 13

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

Question 14

what are the advantages of intravenous// intramuscular drug administration

Answer 14

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

Question 15

what are the disadvantages of intravenous/ intramuscular drug administration

Answer 15

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

Question 16

how does transdermal and subcutaneous drug administration work

Answer 16

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

Question 17

what are the advantages of transdermal and subcutaneous drug administration

Answer 17

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

Question 18

what are the disadvantages of transdermal and subcutaneous drug administration

Answer 18

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

Question 19

what is drug bioavailability

Answer 19

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

Question 20

how can bioavailability of drugs be modified

Answer 20

pharmaceutical factors: dosage, formulation, route of administration

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

Question 21

what is drug distribution

Answer 21

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

Question 22

describe the route of drug distribution

Answer 22

• 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

Question 23

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

Answer 23

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

Question 24

what is planning drug use based on the idea of

Answer 24

body compartment model

Question 25

describe the single compartment model for planning drug use

Answer 25

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

Question 26

describe the two compartment model for planning drug use

Answer 26

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

Question 27

explain volume of distribution

Answer 27

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

Question 28

advantage of drugs with lipid binding in tissues

Answer 28

slow release from accumulation gives the drug a more prolonged effect

Question 29

describe how drugs are prepared for elimination from the body

Answer 29

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

Question 30

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

Answer 30

cytochrome p450 mono-oxygenate system

Question 31

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

Answer 31

this is how drugs are excreted from the body

Question 32

what does the most extensive secretion if drugs occur through

Answer 32

renal excretion of water soluble metabolites via urine liver metabolism and excretion via bile lungs via inhaled gases and volatile fractions of other drugs

Question 33

what are the drugs related to plasma concentration excreted through

Answer 33

sweat saliva tears

Question 34

what are the three stages to drug elimination through the kidneys

Answer 34

glomerular filtration reabsorption secretion

Question 35

how can renal disease interfere with drug excretion

Answer 35

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

Question 36

how can liver disease interfere with drug excretion

Answer 36

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

Question 37

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

Answer 37

depending on the organ function and which drug is being used

Question 38

what is the plasma half life of a drug

Answer 38

this is the time taken to eliminate half of the drug

Question 39

describe first order kinetics in relation to drugs

Answer 39

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

Question 40

describe zero order kinetics in relation to drugs

Answer 40

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

Question 41

Answer 41

first order kinetics

Question 42

Answer 42

first order kinetics

Question 43

Answer 43

zero order kinetics

Question 44

Answer 44

zero order kinetics

Question 45

describe elimination of blood alcohol

Answer 45

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

Question 46

what happens if drug dosing is too frequent

Answer 46

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

Question 47

what happens if drug dosing is too infrequent

Answer 47

will result in sub therapeutic plasma levels and no clinical effect

Question 48

summarise paracetamol overdose

Answer 48

- 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

Question 49

which route of drug absorption is the least reliable

Answer 49

oral route