Pharmacology - drug ADME

Question 1

what is pharmacodynamics

Answer 1

what a drug does to the body

Question 2

what is pharmacokinetics

Answer 2

what body does to a drug eg absorption, distribution, metabolism

Question 3

what is medicine

Answer 3

a combo of drugs and other substances for healing

Question 4

what are receptors

Answer 4

macromolecules on/ in cells that mediate hormones

Question 5

what is an agonist

Answer 5

binds to receptor and produces cellular response

Question 6

what is an antagonist

Answer 6

reduces/ blocks the actions of an agonist by binding to same receptor

Question 7

what is affinity

Answer 7

the strength of bond between receptor and agonist (slow dissociation rate = high affinity_

Question 8

what is efficacy

Answer 8

ability to evoke a cellular response

Question 9

what do antagonists have

Answer 9

affinity but not efficacy

Question 10

what is EC50

Answer 10

agonist % when the response is half of it’s maximum

Question 11

what is potency

Answer 11

lower conc = higher potency. less needed to do the job

Question 12

in competitive agonists and antagonists, what does this have on EC50

Answer 12

shifts curve to right, more is needed to get response

Question 13

in non-competitive antagonists what effect is there on EC50 if you increase conc

Answer 13

none, cannot increase active receptors

Question 14

what is absorption

Answer 14

process by which a drug enters the body from it’s site of administration

Question 15

what is distribution

Answer 15

process by which drugs enter blood and tissues

Question 16

what is metabolism

Answer 16

conversion of drug to less active form

Question 17

what is excretion

Answer 17

process which removed drug from body

Question 18

what factors affect absorption (4)

Answer 18

solubility, stability (not destroyed in acid stomach), lipid to water partition coefficient (lipid soluble), degree of ionisation (unionised)

Question 19

when pKa = pH what does this mean for the drug

Answer 19

it is 50% ionised 50% not

Question 20

what is the equation for week acids

Answer 20

pH = pKa + log ([A-]/[AH])

Question 21

what is better absorbed weak or strong acids and bases

Answer 21

weak

Question 22

where are weak acids normally absorbed

Answer 22

stomach lumen

Question 23

where are weak bases normally absorbed

Answer 23

small intestine

Question 24

what is oral availability

Answer 24

fraction of drug that enters blood stream after ingestion

Question 25

what is systemic availability

Answer 25

fraction that enters systemic circulation after absorption

Question 26

what are some enteral drug routes

Answer 26

oral, sublingual, rectal

Question 27

what are some parenteral drug routes

Answer 27

IV, IM, topical, inhalation

Question 28

which drugs are more able to move around water compartments by diffusion

Answer 28

unionised

Question 29

what is volume distribution (Vd)

Answer 29

volume in which a drug is dissolved (dose/ plasma conc)

Question 30

a Vd of less than 10 indicates the drug is where

Answer 30

vascular compartment

Question 31

a Vd of 10-30 means what

Answer 31

drug is in extracellular compartment

Question 32

Vd of more than 30 indicates what

Answer 32

drug is in total body water

Question 33

what is the MEC

Answer 33

minimum effective concentration

Question 34

what is the MTC

Answer 34

maximum tolerated concentration

Question 35

what is the therapeutic ratio

Answer 35

MTC/MEC, safe drugs have a high ratio, unsafe have a low ratio

Question 36

why does a low MTC/MEC mean a drug is unsafe

Answer 36

because there is a risk of poisoning the patient

Question 37

how is the initial concentration for a drug determined (Co)

Answer 37

D/Vd | mass / volume of blood

Question 38

what to later concentrations depend on

Answer 38

elimination rate constant (Ke)

Question 39

what is Ke

Answer 39

elimination rate constant, the fraction of a drug eliminated per unit time

Question 40

what is first order kinetics

Answer 40

rate of elimination is proportional to drug conc (half life)

Question 41

what is this half life

Answer 41

the time it takes for a drugs conc to half

Question 42

what is the equation for t1/2

Answer 42

0.693/Kel

Question 43

does first order kinetics change half life or Ke of a drug

Answer 43

no and no

Question 44

what is clearance (CL)

Answer 44

volume of plasma cleared of a drug per unit time (norm = L/hr)

Question 45

what is Cp

Answer 45

plasma absorption

Question 46

what is the equation for the rate of elimination

Answer 46

CL x Cp

Question 47

what is steady state

Answer 47

rate of drug admin = rate of drug elim

Question 48

what is Css

Answer 48

steady state concentration of a drug

Question 49

after how many half lives is Css normally achieved

Answer 49

5

Question 50

in oral dosing what should plasma conc fluctuate around

Answer 50

average steady state value

Question 51

what is a loading dose

Answer 51

an originally higher dose given at the beginning of a course to increase time to reach steady state for drugs with long half life

Question 52

what is zero order kinetics

Answer 52

drugs eliminated at a constant rate, changes to first at low concs

Question 53

what are drugs (x..)

Answer 53

xenobiotics, foreign chemicals

Question 54

what does metabolism do

Answer 54

coverts parent drugs to more polar metabolites that are not as readily absorbed in renal tubules and so excreted

Question 55

what organ carries out most drug metabolism

Answer 55

liver

Question 56

what are the 2 faces of drug metabolism

Answer 56

``` 1 = oxidation, reduction, hydrolysis 2 = conjunction ```

Question 57

where does phase 1 occur

Answer 57

Right hand side of liver

Question 58

where does phase 2 occur

Answer 58

left hand side of liver

Question 59

what is the purpose of phase 1

Answer 59

makes it more polar (ionised) by adding a reactive group

Question 60

what is the purpose of phase 2

Answer 60

adds an endogenous compound (carbon) to increase polarity

Question 61

what do CYP450 proteins do

Answer 61

haem proteins that oxidate drugs in phase 1 by monooxygenase cycle

Question 62

what is a common phase 2 reaction and what enzyme carries it out

Answer 62

glucuronidation, UDP-glucuronyl transferase

Question 63

what are the major organs involved in drug excretion

Answer 63

kidneys

Question 64

what are the 3 main processes involved in excretion

Answer 64

glomerular filtration, active tubular secretion and passive reabsorption by diffusion

Question 65

drugs must be in what state to enter filtration via glomerular filtration

Answer 65

unbound

Question 66

a drugs molecular weight (MW) must be under what to be excreted via glomerular filtration

Answer 66

less than 20,000

Question 67

in tubular excretion, what 2 transporter systems actively secrete drugs into nephron lumen

Answer 67

organic anion transporter (OAT - acidic drugs) and organic cation transporter (OCT - basic drugs)

Question 68

why is tubular excretion potentially the most effective (3)

Answer 68

1) max clearance even in bound proteins (to plasma), 2) can concentrate drugs against electrochemical gradient 3)each transporter has maximum Tm for drug

Question 69

what is passive reabsorption

Answer 69

concentration of urine favours passive reabsorption across distal tubule by diffusion

Question 70

what factors affect rate of reabsorption

Answer 70

lipid solubility, polarity, urine flow rate, urine pH