drug therapy

Question 1

discuss physio-chemical factors that affect the transfer of drugs across cell membranes

Answer 1

molecular size 
conc gradient
thickness of membrane
surface area 
type of transport

Question 2

factors that affect absorption of a drug from GI tract

Answer 2

gastric emptying
motility
surface area
passive/active transport

Question 3

medical importance of first pass metabolism

Answer 3

since liver metabolises many drugs, sometimes to an extent that only a small amount of the active drug leaves the liver to circulatory system. the first pass through liver may greatly reduce the bioavailability of the drug

Question 4

benefits of intravenous medication

Answer 4

being able to control dose and delivery speed

ensuring drug remains in system for longer period of time

Question 5

benefits of topical medication

Answer 5

fewer GI difficulties risks - diff individuals absorb med at diff rates
fewer risks of abuse
easy to administer
reduced hosp congestion

Question 6

benefits of inhaled medication

Answer 6

localised to target organ , allowing for lower dose - necessary with systemic delivery , therefore, fewer and less severe adverse effects

Question 7

processes of Phase 1 and 2 metabolism

Answer 7

phase I = oxidation, reduction or hydrolysis of parent drug, resulting in conversion to polar molecule
phase II = conjugation by coupling drug or metabolites to another molecule

Question 8

role of cytochrome P450

Answer 8

oxidise substances using iron and able to metabolise a large variety of xenobiotic substances - plants, drugs, pesticides etc
clearance of various compounds
hormone synthesis and breakdown

Question 9

discuss factors, including drugs, which may inhibit or induce drug metabolism with medically relevant examples

Question 10

pharmacogenetics

Answer 10

how genes affect the way a person responds to meds

Question 11

pharmacokinetics

Answer 11

what body does to drug

Question 12

factors that affect absorption

Answer 12

gastric emptying - slower in older person
motility - reduced for older person
surface area - unchanged
diffusion/active transport -

Question 12

factors that affect absorptionp

Answer 12

gastric emptying - slower in older person
motility - reduced for older person
surface area - unchanged
diffusion/active transport -

Question 13

factors affecting distribution

Answer 13

blood volume - reduced by 8% in older person
blood flow - reduced CO
transport proteins - reduced albumin
body mass composition - significant increase in fat by 35% , decrease in lean muscle mass , TBW reduced
vol. distribution of polar drugs is reduced
vol. distribution of lipophilic drugs is increased

Question 14

factors affecting metabolism

Answer 14

metabolism can happen in kidney, skin, brain and liver (predominantly)
liver blood flow - reduction by 20-50%, reduction in hep. mass
liver clearance - enzymes CYP450 reduced

Question 15

factors affecting excretion

Answer 15

GFR - glomerular filtration rate

reduced in elderly by 50%, reduction by 60% glom.

Question 16

pharmacodynamics

Answer 16

what drug does to body

Question 17

absorption

Answer 17

way drug goes from administration and into the blood

Question 18

distribution

Answer 18

once drug in blood where is it distributed - pathway

Question 19

metabolism

Answer 19

how does it chemically alter the drug - activation/inactivation

Question 20

excretion

Answer 20

way drug moves out of the body

Question 21

transportation methods of drugs into blood

Answer 21

passive - fat soluble drug, water soluble via aquaporins
facilitated - water soluble (larger) via channel
active - transport system with ATP
bulk / endocytosis - membrane engulfs and passes through

Question 22

routes of admin.

Answer 22

GI tract - capsules, syrups, tablets

Question 23

first pass metabolism

Answer 23

drug has to firstly pass through liver to be metabolised before being distributed
happens via portal venous system

Question 24

bioavailability

Answer 24

from dose how much makes it into the plasma

Question 25

GTN absorption method

Answer 25

sub-lingually

higher bioavailability

Question 26

topical administration

Answer 26

fat-soluble drugs

steroids ,

Question 27

subcutaneous route

Answer 27

fat = not good blood supply (5%)

slow absorption drugs

Question 28

intramuscular

Answer 28

75% bioavailability

10-15% of blood flow goes to muscle

Question 29

intravenous

Answer 29

complete bioavailability

Question 30

elimination

Answer 30

primary organ = kidney

1. glomerular filtration - once water soluble can be excreted out
2. tubular secretion - blood -> urine
3. reabsorption - any molecule in urine -> lipid soluble be put into blood via nephron

also, via skin, breast milk, breathing and bile…