pharmacokinetics

Question 1

what is pharmacokinetics

Answer 1

processes that affect the bioavailability of a drug to its target

Question 2

what are the areas that affect the pharmacokinetics

Answer 2

Absorptions from site of administration
Distribution
Metabolism
Excretion

Question 3

what does bioavailability mean

Answer 3

the fraction of administered dose that reaches the system

Question 4

what are different enteral routes for administration

Answer 4

• oral
• sublingual
• rectal

Question 5

what is first pass metabolism

Answer 5

drugs passing through the GIT pass through the liver and are partially metabolized reducing drug for distribution

Question 6

what are the parenteral routes of administration

Answer 6

• IM
• subcutaneous
• IV

Question 7

what are additional routes of administration

Answer 7

• epithelial surfaces
• transdermal
• inhalation
• IO

Question 8

what effects the rate of absorption

Answer 8

• route of administration
• environment where the drug is absorbed
• physiochemical nature of the drug

Question 9

how does blood flow affect absorption

Answer 9

increased blood flow increases absorption causing immediate effect

Question 10

how does food affect absorption

Answer 10

• after a meal slower absorption from small intestine delay
• increase splanchnic blood flow increase rate of absorption

Question 11

how does pH affect absorption - acidic

Answer 11

acidic drug going into an acidic area needs to be unionized as this makes them lipid soluble to be absorbed

Question 12

how to ph affect absorption - weak base drug in acidic

Answer 12

weak base drugs in acidic area for salts (ionised which cant bas through the bilayer - absorption needed in intestine

Question 13

how does drug solubility affect absorption

Answer 13

different drug forms are absorbed faster eg aqueous is faster and more completely than tablet or suspension

Question 14

what is the affect of chemical instability in absorption

Answer 14

different drugs are unstable in different ph concentrations

Question 15

what is distribution

Answer 15

delivery of drugs from the systemic circulation to extracellular fluids/ tissue

Question 16

what is the blood brain barrier

Answer 16

tightly joined endothelial cells that stop drug access to the brain

Question 17

how do drugs become pharmacologically active

Answer 17

• drugs are bound to plasma proteins others are unbound
• unbound drugs are pharmacologically active as they can access different organs and leave the blood stream

Question 18

what occurs at drug competition for protein binding

Answer 18

• higher affinity for plasma are administered displacing other drugs attached
• what is attached becomes pharmacologically active

Question 19

drug distribution calculation

Answer 19

Vd = Q/Cp
Q = amount of drug
Cp = plasma concentration

Question 20

what does the drug distribution show

Answer 20

• small Cp, Vd is high so drugs widely distributed
• high Cp, Vd is small so drug no widely distributed

Question 21

what is phase 1 metabolism

Answer 21

conversion of lipophilic molecules into more polar molecules by the cytochrome system

Question 22

what is phase II metabolism

Answer 22

conjugation of the drug of it metabolites with glucuronyl sulphate, methyl, acetyl moiety

Question 23

what is the purpose of phase I and II metabolism

Answer 23

lipophilic drugs becoming more polar and are conjugated with other metabolised to become more water soluble for excretion

Question 24

what happens to active drugs in metabolism

Answer 24

entering phase I and II they become less active

Question 25

what happens to non active drugs in metabolism

Answer 25

entering phase I and II they become more active

Question 26

what physiological factors affect microsomal enzyme activity

Answer 26

- age - sex - hormones - nutrition

Question 27

how does nutrition affect microsomal enzyme activity

Answer 27

some foods act as an enzyme inhibitor so the drug accumulates leading to toxic effects

Question 28

how do environmental factors affect microsomal enzyme activity

Answer 28

- stress - foreign compound - drugs

Question 29

how do enzyme inhibitors affect microsomal enzyme activity

Answer 29

- competition for CYP enzyme active site - drug with a greater affinity inhibits its own metabolism and decrease metabolism of unrelated drugs

Question 30

how do enzyme inducers affect microsomal enzyme activity

Answer 30

- enhance enzyme activity - accelerating metabolism and activity of enzyme and drug - causing therapeutic failure

Question 31

what is non-microsomal oxidations

Answer 31

metabolism of enzymes outside of the liver

Question 32

what causes the oxidation of noradrenaline

Answer 32

monoamine oxidase - forming noradrenaline aldehyde

Question 33

what is excretion

Answer 33

process of drug removal from internal to external environment

Question 34

what does the kidney excrete

Answer 34

water and soluble drugs as the kidney also absorbs water

Question 35

how does kidney failure affect excretion

Answer 35

drug accumulation as less processing

Question 36

what is an ionized drug

Answer 36

a drug composed of ions

Question 37

what is an unionized drug

Answer 37

a drug with no charge

Question 38

how are ionized drugs excreted

Answer 38

they are unable to pass through the phospholipid bilayer so are excreted

Question 39

how are unionized drugs excreted

Answer 39

they are reabsorbed by passive diffusion back into the body

Question 40

where would a drug be ionised

Answer 40

a weak base areas with an acidic drug

Question 41

where would a drug be unionised

Answer 41

a weak base area with a weak drug

Question 42

what are extra renal routes of excretion

Answer 42

- lungs - milk - biliary system and faecal route - skin - hair - tears - saliva - sweat

Question 43

what is medication half life

Answer 43

the time required for a drug to be eliminated by half of its blood concentration level

Question 44

what affects the medication half life

Answer 44

metabolization

Question 45

when is a steady state reached in half life

Answer 45

around 5 times the half life

Question 46

what is clearance

Answer 46

the volume of plasma apparently cleared of drug in unit time

Question 47

what is the cause of slow clearance

Answer 47

these drug will accumulate so needed a less frequent lower dose

Question 48

what is the cause of a high clearance drug

Answer 48

removed faster so need a higher dose with a therapeutic dose given

Question 49

what is ion trapping

Answer 49

trapping the drug in the form of ions making it more soluble to be easily excreted

Question 50

how does urine ph affect excretion

Answer 50

a weak acid or base can be more ionised in urine so easily excretion

Question 51

when does ion trapping occur

Answer 51

intoxication to increase renal excretion of certain drugs and toxins