Quantitative Aspects of Drug Action Flashcards

1
Q

Drug definition

A

A chemical compound that when applied to a biological system alters its function in a specific manner

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

affinity definition

A

chemical forces involved in the association of a drug with the receptor. Determine occupation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

efficacy definition

A

ability of a drug to activate the receptor and produce a response. Determines activation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

agonist definition

A

molecule that binds to receptor and produces a response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

antagonist definition

A

molecule that binds with high affinity but zero efficacy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

therapeutic window definition

A

a range of doses that produce a therapeutic response without causing significant adverse effect in patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is above the therapeutic window + below?

A

above- side effects

below- sub-therapeutic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

therapeutic index definition

A

Ratio between the minimum effective concentration and the minimum toxic concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

EC50 definition

A

the minimum effective dose for 50% of the population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

LD50 definition

A

the lethal dose of a drug for 50% of the population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

four main processes of pharmokinetics when a drug is taken +

A

ADME

Absorption- process of drug entering the systemic circulation

Distribution- movement from body fluids to organs/compartments

Metabolism- breakdown of drugs

Excretion- removal of drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

different factors that affect absorption

A

charge, lipophilicity, size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why is lipid solubility important?

A

need to diffuse through lipid bilayer of epithelia to enter circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

are drugs generally acidic or basic + why is this important?

A

generally weak acids and bases so equilibrium is weighted towards non-ionised forms at 7.4 pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

pKa definition

A

the pH were the drug exists as 50% ionised and 50% unionised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

where are acidic drugs absorbed? why?

A

stomach, were the pH is 3 so less likely to become ionised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

where are basic drugs absorbed + why?

A

small intestine, where the pH is 9 so less likely to become ionised

18
Q

partition coefficient definition

A

measure of the relative solubility of a compound in aqueous and lipid environments, critical determinant of drug absorption

ratio of lipid solubility to aqueous solubilty

19
Q

what does a high partition coefficient mean? + what can it lead to?

A

more membrane soluble

some drugs remain trapped in body fat

20
Q

distribution definition

A

how drugs equilibrate after entering the body

21
Q

at equilibrium what can be said about the distribution of the drug?

A

concentration of the nonionised molecules is the same in each compartment

there is more drug in larger body compartments

22
Q

volume of distribution definition

A

the volume of fluid required to contain the total amount of drug in the body at the same concentration as that is present in the plasma

23
Q

volume of distribution formula

A

dose/plasma concentration

24
Q

what does the volume of distribution represent?

A

the degree to which a drug is distributed in body tissue rather than plasma

25
what does a higher Vd mean?
greater amount of tissue distribution
26
plasma protein effect
bind to free drugs reduce their ability to diffuse into tissue fluid, reducing renal clearance of drugs
27
where does drug metabolism mainly take place?
liver
28
two phases of metabolism + briefly processes that occur
phase 1- oxidation and reduction, hydrolysis phase 2- conjugation using glycine, glutathione, methylation, acetylation, sulfation
29
clearance definition
volume of plasma that is cleared of drug per unit of time does not say how much drug is cleared, as this depends on volume of distribution
30
clearance equation
rate of elimination/plasma concentration
31
what does chemical modification do to the drug?
inactivates it
32
half life definition
the period of time required for the concentration or amount of a drug in the body to be reduced by half
33
what does a drug's plasma half life depend on?
how quickly it is excreted or translocated to another compartment of destroyed governed by clearance and distribution
34
elimination is first order, what does this mean?
the time taken for half the drug to be eliminated is constant
35
what is done to maintain prolonged therapeutic activity?
repeated oral dose regimens
36
what does the time profile for repeated oral dose regimens look like?
concentration of drug drops after each dose but no longer drops as far as it did before eventually begins to plateau
37
time profile for continuous intravenous infusion described
drug is infuesed for a long period of time at a constant rate concentrations increase until they approach a constant concentration this is where the rate of elimination is equal to the infusion rate
38
why must drugs be metabolised?
need to be made polar so they can be excreted from the body (prevents reabsorption)
39
where may drugs be uptaken? + found in main two excrements
gut bile and urine
40
renal effect
lipid solubility and pKa can effect excretion at the kidneys if the urine is acidic/alkaline the drugs may become non ionised or ionised and thus reabsorbed or excreted