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PathoPhysiology > Exam Two - Introduction to PK > Flashcards

Exam Two - Introduction to PK Flashcards

1
Q

First Pass Metabolism (Effect)

A

liver breaks down absorbed meds (via portal circulation) BEFORE drug reaches systemic circulation, may significantly REDUCE concentration attainable in body. This may completely prevent some drugs via oral route. Reflected in reduced bioavailability (F)

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2
Q

F

A

Bioavailability

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3
Q

Bioavailability

A

fraction of PO reaching systemic circulation when compared to IV standard of 1

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4
Q

PO

A

oral meds

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5
Q

ADME

A

absorption
distribution
metabolism
excretion

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6
Q

Absorption factors affecting PK (ADME)

A
  • stomach pH, GI motility, GI blood flow, fed/fasted, drug solubility, drug dissociation, molecule charge, drug-food interactions
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7
Q

Distribution factors affecting PK (ADME)

A
  • patient’s Vd (volume of distribution) - (pregnancy, burns, cachexia), cardiac output, tissue perfusion (diabetics), limb loss
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8
Q

Metabolism factors affecting PK (ADME)

A

liver function (impacts of cancer, hepatitis), drug interactions, nutritional status, perfusion of liver

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9
Q

Excretion factors affecting PK (ADME)

A

renal function, some biliary considerations

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10
Q

Actual (total) BW

A
  • scale weight “as is”
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11
Q

Ideal BW

A

calculation based upon population averages, what we think someone should weigh for a given height/sex

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12
Q

Adjusted BW def

A

educated WAG. calculation to adjust dosing of some drugs in obese patients. attempt to prevent over and over dosing. often used in patients who are > 30% IBW

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13
Q

formula for adjusted BW

A

= IBW + 0.4(TBW-IBW)

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14
Q

formula for male ideal body weight

A

50 + 2.3(each in >60”) = _____kg

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15
Q

formula for female ideal body weight

A

45.5 + 2.3(each inch >60”) = __________kg

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16
Q

How does losing a limb affect BW?

A

lose a percentage of weight

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17
Q

How do you adjust IBW for paraplegia?

A

subtract 5-10%

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18
Q

how do you adjust IBW for quadriplegia?

A

subtract 10-15% from IBW

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19
Q

Why do we adjust IBW for para/quadriplegia?

A

loss of muscle tone in limbs

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20
Q

What is the most common reason for LE amputations?

A

Diabetes

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21
Q

Obesity def

A

BMI of 30 or higher

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22
Q

What does BMI measure?

A

measure of an adult’s weight in relation to height

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23
Q

BMI formula

A

BMI = weight (kg)/ height (m^2)

24
Q

1 kg = _____ lbs

A

2.2

25
Q

1 in = _____ cm

A

2.54

26
Q

PK implications of obesity for distribution

A

-higher % of body fat could make a drug resevoir
- lower % of lean tissue and body water

27
Q

PK implications of Obesity for metabolism

A
  • higher cardiac output
  • enlarged liver with variable effect on metabolic pathways
28
Q

PK implications of Obesity for excretion

A
  • high renal blood flow
  • higher GFR
29
Q

GFR

A

glomerular filtration rate

30
Q

What is GFR important for?

A

dosing drugs with renal clearance
important in elderly
impacts clearance and excretion

31
Q

CrCl

A

creatinine clearance

  • typically estimated, need 24 hr urine to measure
32
Q

compare GFR with CrCl

A

CrCl usually higher

33
Q

What formula is used to estimate CrCl?

A

cockcroft-Gault eq

34
Q

male cockcroft-gault eq

A

((140-age in years)weight kg)/(72 x SCr)

35
Q

female cockcroft eq

A

male * 0.85

36
Q

Css

A

drug concentration in the body at steady state. takes 3-5 drug half-lives to attain steady state

37
Q

Half-life (T1/2)

A

time for drug level to decay by half. half life affects dosing interval

38
Q

peak

A

css max, or “high point” after infusion

39
Q

trough

A

css min, or “low point” just PRIOR to next influsion

40
Q

AUC

A

area under curve
- calc or trapezoidal rule! drug exposure

41
Q

fist order kinetics

A

amount eliminated over time changes, but fraction eliminated is constant (8,4,2,1mg…)

42
Q

zero order kinetics

A

amount of drug eliminated does not change with concentration remain, but fraction eliminated does

43
Q

pro-drug

A

administered in inactive form, need the liver to activate it! convert to active form in body via metabolic process, may avoid destruction in GI tract, avert first-pass metabolism, reduce toxicity, etc.

43
Q

CYP 450 system

A

inhibition and induction
- major factor in drug-drug interactions.
-leads to sub-therapeutic response or potential toxicity

43
Q

inhibition CYP 450

A

enzyme inhibitors block metabolism of substrate which leads to increased concentration of said substrate in body (EX- nirmatrelvir/ritonavir )

43
Q

Vd

A

volume of distribution

43
Q

induction CYP 450

A

enzyme inducers accelerate metabolism of substrate which leads to decreased concentration of said substrate in body

44
Q

volume of distribution

A

fake number
- a volume that would be required to account for all drug in body if it were present in same concentration as plasma
- expressed in L/kg

45
Q

Drugs with ______ Vd readily distribute in body

A

large

46
Q

Drugs with ______ Vd tend to keep significant amounts in circulation and ____ easily distribute in tissues

A

large, less

47
Q

MD

A

maintenance dose

48
Q

Maintenance dose

A

ongoing dose required to maintain a given plasma level accounting for drug LOSS.removal from body via metabolism/excretion. Greatly impacted by drug clearance

49
Q

LD

A

loading dose

50
Q

loading dose

A

dose to rapidly initally achieve a desired plasma concentration

51
Q

formula for LD

A

= (concentration desired x Vd)/(F)

52
Q

LD impacted by ____________, MD impacted by _____________

A

volume, clearance

PathoPhysiology (29 decks)

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