Issar- Pharmacokinetics 1 and 2 Flashcards

1
Q

what reaction proceeds at a constant rate and is independent of concentration of drug A present in the body?

A

zero order rate (ex. alcohol)

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

describe first order rate constant.

A

describes a proportional rate of change of drug A with time (linear)

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

what makes up the characteristics of a compartment?

A

not real anatomic region, uniform distribution within each, open system, well-stirred, rates constants represent drug entry or exit

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

what type of drugs show/demonstrate nonlinear pharmacokinetics or zero-order reactions?

A

drugs with accumulation in the plasma levels

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

what do most processes of ADME follow?

A

first-order reactions

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

what happens to first-order drugs if you increase the amount of drugs until system is saturated (ex. overdose)?

A

drug will change from first-order to zero-order (mixed-order kinetics) - phenytoin and salicylic acid

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

what happens to a drug in a one-compartment model?

A

achieves instantaneous distribution throughout body and between tissues and follows first order kinetics

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

what happens to a drug in a two-compartment model?

A

drug distributes between central and peripheral compartment - but not instantaneous distribution (biphasic response)

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

what is the equation for Vd? and what is it used for clinically?

A

Vd = amount of drug in body/concentration in plasma; calculate appropriate blood concentration of drug in patient

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

what is the equation to calculate an appropriate dose of a drug?

A

Dose = Cp x Vd

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

what is drug clearance?

A

the volume of plasma fluid that is cleared of drug per unit of time (not how much drug is being removed)

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

what is the equation for body Cl?

A

Cl body = elimination rate/plasma concentration

(dDb/dt)/Cp or -kelim x Vd

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

what is half-life?

A

time it takes for plasma concentration of drug to fall by 50% regardless of initial value - meaningful if drug follows first-order kinetics

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

How do you calculate half-life?

A

half-life = 0.693/Kelim
T 1/2 = (0.639 x Vd)/Cl
Kelim = Cl/Vd

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

what happens to half-life if there is a decrease in Vd and an increase in clearance?

A

half-life will be shortened

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

What is it called when the infusion rate matches the elimination rate for a drug?

A

steady state (Css = rate of infusion/clearance)

17
Q

why would you use a loading dose?

A

to achieve steady state faster with an infusion (loading dose = target concentration x Vd) - drugs with long half lives

18
Q

what is the relationship between accumulation period and half life?

A

after the time for the first half life has occurred to drug will be at half the projected Css (Css takes about 3-4 half lives)

19
Q

what is pharmacokinetic accumulation?

A

occurs when a dose is given while there is a large residue still present in the body (drug has slower elimination rate)

20
Q

why does pharmacokinetic accumulation not happen indefinitely?

A

dosing intervals - the drug has reached Css and elimination = incoming dose

21
Q

What is the equation for Css Average?

A

Css,Avg = (F x D)/ Cl x tau

22
Q

what are the 3 factors that influence extent of fluctuation?

A

half-life, dose division, and dosage form (Half-life is the most influential)

23
Q

why are short half-life drugs problematic? and what are 2 ways to moderate it?

A

produce more fluctuations and brings risk of complications - dose division and slow release formulas

24
Q

why does dose division reduce drug fluctuations?

A

giving the dose at more frequent intervals and smaller doses keeps concentration in desirable range instead of oscillating between toxic and effective (be careful with non-compliance)

25
Q

how do slow release formulas help decrease drug fluctuations?

A

slow release gives a shorter period of decline and the low troughs are eliminated