Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biopharmaceutics > pharmacokinetics > Flashcards

pharmacokinetics Flashcards

1
Q

what is pharmacokinetics

A

relationship between dose and time course of drug concentration attained in different regions of the body during and after dosing

(what the body does to the drug basically)

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

what is pharmacodynamics

A

relationship between drug conc/time profile and therapeutic and adverse effects

(basically how the drug affects the body)

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

why is pharmacokinetics relevent

A

allows prediction of time course of drug action

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

why are drugs with a narrow therapeutic range not good

A

difficult to use, patient might need to be monitored frequently (therapeutic effects, side effects, blood level)

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

what does ADME stand for

A

absorption- movement of drug form site of administration to site of measurement

distribution- reversible transfer of drug within body

metabolism- loss of drug from body by chemical conversion

excretion- loss of unchanged drug from body

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

what is elimination in ADME

A

irreversible loss of drug from body (metabolism and excretion) (ME)

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

what is disposition in ADME

A

process of elimination and distribution (distribution, metabolism and excretion) (DME)

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

name things that affect absorption

A

passive diffusion- ficks first law

lipophilicity (partition coefficient)- lipid soluble drugs have higher permeability and polar ionised compounds have lower permeability

size- small water soluble drugs can pass between cells easily, size affects diffusion rate

ionisation- pH affects ionisation and lipophiliicty, charged drugs are slower

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

what is bioavailability

A

fraction of administered dose reaching systemic circulation in an unchanged form

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

describe the causes of reduced bioavailability in oral administration

A

loss in faeces, decomposition in lumen, destruction within walls of GI tract (intestinal first pass metabolism), destruction within liver (hepatic first pass metabolism)

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

how is drug transported

A

blood

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

what is volume of distribution and its equation

A

Vd= total amount of drug in body/plasma drug concentration

describes relationship between amount of drug in body and the concentration in blood

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

name 1 thing that majorly determines Vd (volume of distribution)

A

strength of drug binding to tissue components compared to plasma proteins

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

name 2 main routes of elimination of drugs and where it mostly occurs

A

excretion and metabolism

mostly in kidney and liver
kidney- excreted unchanged
liver- metabolised then excreted

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

difference between drug elimination in kidney and liver

A

kidney- drug is excreted unchanged
liver- drug gets metabolised then excreted

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

name 2 major independent pharmacokinetic parameters

A

volume of distribution and clearance

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

what is clearance

A

volume of blood cleared of drug per unit time (L/hr, mL/min)

describes efficiency of irreversible elimination of a drug molecule from systemic circulation, can be through excretion or metabolic conversion to a metabolite (metabolite in body but parent molecule is cleared)

(uptake into tissue isnt clearance if unchanged drug eventually returns to circulation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is extraction ratio and its equation

A

E=1-(Cv/Ca)

0<E<1
0=no extraction 1=complete extraction

an organs efficiency in eliminating drug from the systemic circulation over 1 pass through the organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the equation for clearance

A

clearance= Q x E

Q=blood flow to organs
E= extraction ratio of organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is clearance

A

volume of blood completely cleared of drug per unit of time, (can be hepatic clearance, renal clearance, pulmonary clearance etc.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the equation for rate of elimination and the units

A

rate of elimination (mg/hr) = clearance (L/hr) x plasma drug conc (mg/L)

for most drugs the rate of elimination is directly proportional to drug concentration

22
Q

what is the equation for elimination rate constant (K) and what does it depend on

A

K=CL/Vd

elimination rate constant depends on clearance and volume distribution

23
Q

name 2 categories of iv administration

A

bolus (single dose) and infusion (constant rate)

bolus= injection into bloodstream

24
Q

what assumptions are made for the one compartment model for iv bolus

A

body acts as a single and uniform compartment, entire does of drug is injected at once, drug distributes through entire body instantaneously, volume of compartment remains constant, drug elimination starts immediately

25
Q

describe a blood concentration time profile for a one compartment model of iv bolus

A

most drugs show first order elimination kinetics, conc time data show a straight line going down on a semi log plot, on normal plot it curves down

semi log plot= one axis is logarithmic and one is linear

26
Q

what is the unit for elimination rate constant

A

h^-1 (per hour)

27
Q

what is the equation for a plasma concentration at a specific time (t) in single dose iv administrations

A

Ct=C0e^(-kt)

Ct= plasma conc at time t
t= time
C0= initial conc
K= elimination rate constant

28
Q

what is half life and how to calculate it

A

time take for plasma conc to fall by a half

t1/2=0.693/k

(could be worked out from Ct=C0e^(-kt) by setting t as 0.5 and C0 as 1)

29
Q

how to find clearance

A

take frequent blood samples after a single (bolus) iv dose and measure the drug conc in plasma and plot against time, calculate area under drug conc

clearance= dose/auc

30
Q

how to find area under conc/AUC

A

split the graph into trapeziums and use 0.5(a+b)h

31
Q

what is the equation for volume distribution

A

clearance/k

find k using t0.5=0.693/k on graph

32
Q

describe the kinetics of oral absorption

A

mostly first order (curves down), rate of absorption is proportional to the amount remaining to be absorbed

33
Q

the amount of drug in intestinal lumen will decrease with time, the rate of emptying of the lumen will also decrease but why

A

rate of emptying decreases over time because it depends on the amount of drug remaining in the intestinal lumen, rate of emptying is proportional to the amount of drug remaining and the efficiency of absorption

34
Q

what is the equation for rate of absorption in first order oral absorption kinetics and its half life

A

rate of absorption= ka x Aa

Ka= absorption rate constant
Aa= amount remaining to be absorbed

t0.5a= 0.693/ka

35
Q

how to calculate total bioavailability (F)

A

F= Ff x Fg x Fh

Ff= fraction entering intestinal wall tissue
Fg= fraction that survives destruction in intestinal wall
Fh= fraction that survives destruction in liver

x100 if u want %

36
Q

what equation is used to compare the bioavailability of 2 drugs (A and B) and an assumption of it

A

F= (AUC A x Dose B) / (AUC B x Dose A)

assume clearance will be the same

37
Q

if the dose/fraction of dose absorbed was increased while the other factors remained constant what would happen and how it would show on a graph

A

produces a proportional increase in plasma concentrations at all times

graphically the line goes taller/ increased Cmax and AUC while tmax is the same

38
Q

what happens to the graph if everything remains the same but the absorption is slower

A

AUC remains the same, Cmax will be lower and tmax will be higher

39
Q

for constant rate intravenous infusion, what happens to the amount in body (Ab) when
1) input rate < elimination rate
2) input rate> elimination rate
3) input rate=elimination rate

A

1) input rate < elimination rate= Ab decreases
2) input rate> elimination rate= Ab increases
3) input rate=elimination rate= Ab remains constant

40
Q

what is steady state

A

when input rate= output rate

(when graph plateus)

41
Q

how to calculate rate of elimination for constant rate iv infusion

A

rate of elimination= elimination rate constant (Kab) x amount in body (Ab)

42
Q

how to calculate rate of change of drug in body for constant rate iv infusion

A

rate of change of drug in body= rate of infusion - Kab

43
Q

how to calculate volume of distribution at steady state

A

Vd= Ab/Cpss

Cpss= plasma drug conc at steady state

44
Q

how to calculate clearance at steady state

A

CL=K x Vd

45
Q

what is the plasma drug concentration at steady state directly proportional to

A

rate of infusion

46
Q

how to calculate infusion rate of iv infusion

A

Rinf= CL x Cpss

47
Q

how to calculate plasma conc at time t (build up to steady state)

A

Ct=Cpss(1-e^(-kt))

48
Q

when is a loading dose administered

A

to speed up time to target plasma conc (Cpss), useful for drugs with long half lifes if immediate effect is required, provides target Cpss from a single bolus injection

49
Q

how to calculate bolus dose

A

plasma conc (Cpo) x v

50
Q

how to calculate loading dose

A

target plasma conc (Cpss) x v

51
Q

what affects volume of distribution

A

renal/liver failure, dehydration, age, weight

renal failure- fluid retention, increases vd

liver failure- alters body fluid and plasma protein binding, increases vd

dehydration- lowers vd

age- body composition changes as age increases, decreases vd

weight- obese has more fat, vd is greater as drug diffuses into body fat

Biopharmaceutics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions