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Biopharmaceutics > pharmacokinetics cop (mostly equations) > Flashcards

pharmacokinetics cop (mostly equations) Flashcards

1
Q

how to calculate elimination rate constant from a graph

A

k= -(lnC2 - lnC1)/t2-t1

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2
Q

how to calculate half life

A

t1/2= ln2/k

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3
Q

what is the unit for elimination rate constant

A

h^-1 (or any per unit of time)

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4
Q

how to calculate the area under curve

A

AUC= dose/CL or dose/K x Vd

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5
Q

how to calculate clearance

A

CL= K x Vd

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6
Q

units for AUC

A

mg x h/L

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7
Q

how to find AUC on a graph

A

split graph into trapeziums
0.5(a+b)h for all then add conc of last/k

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8
Q

units for clearance

A

volume per unit time eg. ml/min, L/h

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9
Q

how to calculate clearance for IV bolus dose

A

CL= dose/AUC

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10
Q

how to calculate maintenance dose rate and units

A

maintenance dose rate (mg/h) = CL (L/h) x target concentration (mg/L)

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11
Q

how to calculate clearance for oral dosing

A

CL= (F x dose) /AUC

F=bioavailability

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12
Q

how to calculate clearance for intravenous infusion

A

CL = (R x Tinf)/AUC

R=rate of infusion
Tinf= duration of infusion

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13
Q

how to calculate volume of distribution (vd)

A

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

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14
Q

units of vd

A

L (volume)

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15
Q

how to calculate what amount of drug to give

A

amount of drug to give= vd x plasma drug concentration required
(basically vd rearranged)

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16
Q

things that affect volume distribution

A

renal/liver failure, dehydration, age, weight

17
Q

how to calculate vd for IV bolus dose on a graph

A

vd= dose/ C0

C0=conc at time zero

18
Q

how to calculate vd with clearance and elimination rate constant

A

vd= CL/K

19
Q

how to calculate vd for iv bolus

A

vd= dose / (AUC x k)

20
Q

how to calculate vd for oral dose

A

vd= (F x dose )/ (AUC x k)

21
Q

how to calculate vd for intravenous dose

A

vd= (R x Tinf )/ (AUC x k)

22
Q

how to calculate vd with steady state concentration

A

vd = R/Css x k

Css= steady state conc

23
Q

what is bioavailability (F)

A

fraction of administered drug that enters systemic circulation unchanged

24
Q

how to calculate absolute bioavailability in non intravenous drugs

A

absolute bioavailability= (Dose intravenous x AUC non-intravenous) / (Dose non-intravenous x AUC intravenous)

25
Q

what is the bioavailability of any intravenous drug and why

A

1, the absolute bioavailability equation compares non IV routes bioavailability with an IV one

26
Q

how to calculate relative bioavailability and when to use it

A

relative bioavailability= (dose of formulation 1 x AUC of formulation 2) / (dose of formulation 2 x AUC of formulation 1)

use when IV data for bioavailability is not obtained

27
Q

explain what happens when bioavailability of a drug increases (graph)

A

peak time and rate of decrease stats the same, higher plasma drug conc

28
Q

why is bioavailability important

A

measures completeness of absorption of a drug

29
Q

factors that affect bioavailability

A

route of administration, drug formulation, drug metabolism, drugs physical properties, drug interactions with other drugs/food, patient factors

30
Q

how to calculate dose to give using absolute bioavailability

A

dose to give= dose in systemic circulation / absolute bioavailability

31
Q

how to calculate dose in systemic circulation

A

dose in systemic circulation= dose given x absolute bioavailability

32
Q

what is bioequivalence

A

when 2 drugs have similar bioavailability

33
Q

equation using bioavailability, AUC, CL and dose

A

bioavailability= (AUC x CL)/dose

34
Q

what is absorption rate constant (Ka) and its units

A

rate drug is absorbed from site of action into systemic circulation after administration

units= per unit time (eg. h^-1 or s^-1)

35
Q

what does a larger Ka mean

A

faster absorption, higher plasma drug concentration, peak plasma conc will increase, time to reach peak decreases, time for drug to be cleared decreases

36
Q

how to find absorption rate constant

A

Ka= ln2/t1/2 = 0.693/t1/2

37
Q

how to find residual graph from a plasma conc/time graph

A
  1. extrapolate linear part to time 0
  2. find actual conc and extrapolated conc of each time (already linear bits stay the same)
  3. extrapolated-actual conc
  4. plot new concs on same axis and add line of best fit (residual graph)

straight=first order kinetics

38
Q

how to find half life on a residuals graph

A
  1. choose any conc and its time
  2. half the conc and find the time
  3. t2-t1=t1/2

Biopharmaceutics (11 decks)

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