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Neuro II first Exam > Segars: Introduction to Pharmacokinetics > Flashcards

Segars: Introduction to Pharmacokinetics Flashcards

1
Q

What is pharmacodynamics?

A

-how the drugs affect the body

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2
Q

what is pharmacokinetics?

A

-how the body affects the drugs

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3
Q

What is ADME?

A
  • Absorption
  • Distribution
  • Metabolism
  • elimination
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4
Q

what is the most common way that the body absorbs drugs?

A
  • diffusion
  • through cell membranes
  • determined by concentration gradient
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5
Q

what 2 forms are the drugs that you take in when you take them?

A

-either ionized or unionized

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6
Q

do protonated drugs pass through the membrane easily?

A
  • no

- remember kid that has static energy… lots of protons

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7
Q

What are the 2 important areas of the body where pH varies and commonly impacts ionization status?

A
  • GI tract

- Kidneys

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8
Q

When PkA=pH, what is the ratio of ionized and unionized drug?

A
  • 50%:50%

- remember it will always add up to 100%

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9
Q

Which kinds of drugs get absorbed??

A

-unionized drugs

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10
Q

For base drugs, what state will it be in when the pH is high?

A

-unionized (then it can get absorbed)

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11
Q

for acid drugs, what state will it be in when the pH is low?

A

-unionized…. so it works at lower pH’s

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12
Q

What do active processes of absorption require?

A
  • Energy

- they can move across concentration gradients

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13
Q

What are the 2 states of drugs related to serum protein binding?

A
  • bound
  • unbound
  • we are talking about distribution now
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14
Q

Which kind of drug is active, bound, or unbound?

A
  • unbound

- if it is bound to ptn, it can’t work

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15
Q

What is alpha?

A
  • the opposite of % protein bound
  • represents the unbound fraction
  • the smaller the alpha, the smaller the unbound fraction… makes sense
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16
Q

In metabolism of drugs, what is the phase 1 reaction?

A
  • formation of new or modified functional group or cleavage

- CYP450 (oxidation)

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17
Q

What are phase 2 rxns?

A

-involve conjugation with an endogenous substance (covalent linkages; glucouronidation…etc)

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18
Q

3 main processes of elimination

A
  • Passive glomerular filtration
  • Passive tubular diffusion
  • Active tubular secretion
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19
Q

What is First order pharmacokinetics?

A
  • rate of elimination proprtional to Cp, OR
  • Amount of drug removed per unit of time will vary proportionately with Cp
  • the “linear” type of drug
20
Q

What is zero order pharmacokinetics?

A
  • saturable (Vmax)
  • Rate of elimination not proportional to Cp (concentration in plasma), OR
  • fraction of drug removed per unit of time stays the same over time
21
Q

Assuming first order pharmacokinetics, if you have 100mg/mL at max concentration, how much will there be halfway between that point of zero concentration?

A
  • 50mg/mL
  • the fraction lost per unit time never changes
  • remember, for first order, the percent lost is always the same
  • think of it as half-life! keeps’ halving itself
22
Q

What is cool about zero order kinetics?

A
  • we lose the same AMOUNT of stuff each time.

- but we lose a larger PERCENT with each time unit

23
Q

What is MEC

A
  • minimum effective concentration

- look at the drug concentration at the start of duration of action

24
Q

What is one of the key things that determines C min?

A

-dosing frequency

25
Q

What is C min?

A
  • the lowest concentration that your patient will have before you give another dose
  • this helps dictate how often we give a patient a drug
26
Q

How do we determine the amount of drug absorbed?

A

-Dose* Bioavalibility* Salt factor (usually 1)

27
Q

What do we have to know about the volume of distribution?

A
  • The high it is, the more places it can go in our body

- the smaller the number, the less it gets out of the blood vessels and goes other places

28
Q

How do you calculate Ideal Body Weight?

A
  • Women: 45kg+(2.3kg*(height in inches-60 inches))

- Male: same thing but with 50 kg at the beggining

29
Q

If their body weight is something crazy and huge, how do we calculate their adjusted body weight?

A

-(0.4* (ActualBW-IBW))+ IBW

30
Q

What is clearance?

A
  • represent the volume of blood per unit of time that is cleared
  • L/hr
31
Q

What units should Vd be in?

A
  • liters
  • (volume of distribution)
  • so if it is in L/kg, multiply by weight and go nuts
32
Q

What is Tau?

A
  • the dosing interval

- if you give a pill once a day, Tau=24hrs…. once every 24 hrs

33
Q

What is half life?

A
  • the time it takes for the drug concentration to drop by 50%
  • 1st order kinetics have this
34
Q

What is steady state dependent on?

A
  • TIME!!!

- it is when the metabolism starts equalling the amount of drug we put in

35
Q

how many half lives does it take to produce steady state?

A

-4-5 half lives

36
Q

what happens with the number of half lives we go through that progress we have on the steady state curve (it plateus)

A
  • 1 half life…. 50% to steady state

- 2 half lives…. 75% to steady state…. etc

37
Q

If we are AT STEADY STATE, what happens when we double the dose?

A
  • we will double the level
  • if we double the dose, we double the level in the blood… it’s proportional
  • D-D/D-L
38
Q

Amount of drug absorbed

A

-(S)(F)(Dose)

39
Q

Does of different dosage form

A

-amount absorbed from current form/(S)(F) of new dosage form

40
Q

Concentration in plasma (Cp)

A
  • the iced tea thing

- (S)(F)(Dose)/Vd

41
Q

Loading dose

A

-(Vd)(Cp)/(S)(F)

42
Q

Supplemental loading Dose

A

-(Vd)(Cpdesired-Cpinitial)/(S)(F)

43
Q

Clearance

A

-(S)(F)(Dose/tau)/Cp

44
Q

Maintenance Dose

A

-(Cl)(Cp)(tau)/(S)(F)

45
Q

Elimination rate constant (Kel)

A

-(Cl)/(Vd)

46
Q

Half life

A

0.693/Kel

47
Q

How do you calculate creatinine clearance?

A
  • (140-age)IBW (in kgs) / (72SCr)

- * 0.85 if patient is female

Neuro II first Exam (5 decks)

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