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BB Pharmacology > 1 Pharmacokinetics > Flashcards

1 Pharmacokinetics Flashcards

1
Q

Pharmacokinetics

A
  • what the body does to the medication

- body wants gone, ASAP, sees meds as poison

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2
Q

Absorption

A
  • movement of a medication to the blood stream/site of action
  • dependent upon route of admin
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3
Q

ionization

A

dissociation

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4
Q

lipophilicity

A
  • “fat loving”

- less ionized (not changing charge), move across lipid bilayers more easily

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5
Q

hydrophilicity

A
  • “water loving”

- more ionized, more likely to stay in solution/blood

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6
Q

bioavailability

A
  • % of med that reaches systemic circulation
  • IV meds = 100%
  • useful when converting between forms
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7
Q

Salt form

A
  • med + salt = ionized form of drug –> increased solubility

- hydrochloride, sodium, sulfate

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8
Q

Considerations for oral administration

A 
pH
contents
surface area
blood flow
GI motility
gut flora
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9
Q

Sublingual/Buccal dosing

A
  • drains directly into vena cava (ideally 100% bioavailability)
  • must be highly lipid soluble & potent
  • lipophillic, less ionized
  • no first pass
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10
Q

First Pass Metabolism

A
  • drug concentration greatly reduced prior to reaching systemic circulation
  • small intestine –> hepatic circulation –> detox
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11
Q

Topical Administration

A

-must be highly lipophillic for systemic effect

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12
Q

Eye administration

A

careful of nasolacrimal duct –> systemic

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13
Q

Inhalation admin

A
  • large surface area, high blood interaction

- avoid first pass

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14
Q

IV, SQ, IM

A

-same bioavailability, different rates of onset

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15
Q

Simple Diffusion: Rate Limits

A
  • amount of capillaries
  • solubility
  • molecular size
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16
Q

Distribution

A
  • drug moving in blood and through compartments

- ASSUME there is a homogenous mixture throughout all compartments since we only collect blood sample (dumb, but true)

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17
Q

Loading Dose

A

-dose required to reach desired concentration based on calculated volume of distribution
-will not decrease time to steady state
Loading Dose = (Volume of distribution)(desired concentration)

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18
Q

Multi-compartment Model

A

med admin –> compartment 1 (blood) where it can then travel to compartment 2 (major organ systems) OR compartment 3 (fatty tissue)
-moves back to compartment 1 for elimination

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19
Q

Protein Binding

A
  • required for some meds to travel across membraines
  • results in 2 forms of circulating med - bound and unbound
  • competitive - can result in interactions
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20
Q

How does low albumin relate to protein binding meds?

A
  • low albumin –> increased free drug and potential for toxicity
  • ex.) burns, malnutrition, liver/kidney disease
  • change dose
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21
Q

Tissue Binding

A

Fat: reservoir for lipid soluble
Bone (tetracyclines)
Heart (digoxin)

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22
Q

Membrane Permeability

A

-med must permeate all levels of membrane to permeate target organ

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23
Q

Blood Brain Barrier

A

-very protective, difficult to cross

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24
Q

Placental Transfer

A
  • essentially everything mom takes, baby gets
  • fetal plasma is acidic –> ion trapping
  • P-glycoproteins
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25
Q

Qualities of molecules that have a high likelihood to absorb into fetal circulation

A
  • low molecular weight
  • high lipid solubility
  • unbound
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26
Q

P-glycoproteins

A
  • protective, limit transport into cells
  • found all over body (BBB)
  • requires ATP
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27
Q

Passive Diffusion

A
  • no energy required
  • no carrier required
  • slides across
  • rapid for lipophilic, small, nonionic molecules
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28
Q

Facilitated Diffusion

A
  • no energy required
  • NEEDS carrier
  • bond to carrier by noncovalent mech.
  • chemically similar drugs will compete
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29
Q

Aqueous Channels

A
  • no energy required
  • no carrier required
  • small, hydorphilic drugs diffuse along concentration gradient by channels/pores
30
Q

Active Transport

A
  • NEEDS energy
  • NEEDS carrier
  • just like facilitated diffusion except ATP powers drug transport against concentration gradient
31
Q

Metabolism

A
  • breakdown of medication
  • reduces size, increases hydrophilicity (increases ionized)
  • can make drug more or less active
32
Q

Metabolites

A
  • products of metabolism

- may be toxic, active or inactive

33
Q

Metabolism: Phase 1

A
  • exposes functional group (often more ionized)
  • goal is to increase ionization
  • then, hydrolyzed or ester linked for rapid elimination
34
Q

Oxidation

A
  • type of phase 1 metabolism

- loss of electrons via split of O2 molecules

35
Q

Reduction

A
  • type of phase 1 metabolism

- gain electrons via electron transfer

36
Q

Hydrolysis

A
  • type of phase 1 metabolism

- addition of water to break bonds

37
Q

Metabolism: Phase 2

A
  • addition of functional group
  • conjugation reactions- attachment of small hydrophilic endogenous molecule to form water-soluble compound
  • results in larger molecular weight and increased hydrophilicty
38
Q

Enzymes

A
  • catalyst for bio-reactions

- largely produced in liver

39
Q

Cytochrome P450

A

largest family of enzymes responsible to breakdown

40
Q

Subfamilies of CYP450

A

family –> CYP1, CYP2, CYP3, etc
subfamily –>CYP3A, CYP2D
isoforms–> CYP3A4, CYP2D6

41
Q

CYP3A4 & CYP3A5

A

-not the highest amount in the body, but metabolize the greatest amount

42
Q

Inhibition of enzymes

A
  • prevents enzyme from working properly

- cannot give inhibitor & substrate = increased substrate

43
Q

Induction of enzyme

A
  • enhances enzymes ability to work

- cannot admin inducer & substrate = less substrate d/t increased metabolism

44
Q 
ex.) administration of carbamezepine (CYP3A4 inducer)
with midazolam (substrate) will create...
A

difficult induction or early awakening

45
Q

ex.) administration of ketoconazole (CYP34 inhibitor) with midazolam (substrate) will create…

A

prolonged sedation

46
Q

Factors Affecting Metabolism

A

Genetics
Disease- kindey & liver
Age

47
Q

Elimination

A
  • body riding of material
  • unchanged, metabolite or mix of the two
  • easier to eliminate polar, hydrophilic, ionic compounds
48
Q

Renal Elimination

A
  1. ) Glomerular Filtration
  2. ) Active Tubular Secretion
  3. ) Passive Tubular Reabsorption
49
Q

Glomerular Filtration

A
  • renal elimination
  • determined by renal blood flow, GFR, plasma protein binding
  • only free drug is filtered
50
Q

Active Tubular Secretion

A
  • transfer of materials from peritubular capillary to renal tubular lumen
  • opposite of reabsorption
  • active & passive transport
  • important for highly protein bound drugs
51
Q

Passive Tubular Reabsorption

A
  • lipophilic drugs
  • modulated by urine pH & drug pKa
  • attempting to remove water, sometimes get extra
52
Q

First Order Kinetics

A

-constant fraction of drug is removed per unit of time

53
Q

Zero Order Kinetics

A

-predictable, set constant rate

54
Q

Elimination Rate

A

fraction or % of total amount of drug in the body removed per unit of time (hrs)

55
Q

Half Life

A

-amount of time it will take until concentration in the body is half original amount

56
Q

Steady State

A

rate in = rate out

  • drug will be effective at max effect
  • not affected by loading dose
  • requires 5 half lives
57
Q

Interpreting drug levels….

A
  • never take just one value, acknowledge trends

- pt status!

58
Q

Serum Concentations

A

measure trough –> efficacy
measure peaks –> toxicity
*supply staff with painfully precise directions on timing

59
Q

Context Sensitive Half Life

A
  • time it takes after a continuous infusion, at desired concentration, takes to reach half life after stopping medication
  • specific to anesthesia
60
Q

CSHT < half life at time of d/c…

A

med did not have enough time to fully distribute

61
Q

Creatinine Clearance

A

female: 88-128 mL/min
male: 97-137 mL/min
* measure of kidneys ability to breakdown creatine (normal biproduct) and indicative of GFR
- use lower weight when calculating

62
Q

Ideal Body Weight

A

Female:
IBW = 45.5 + (2.3 x inches > 5 ft)

Male:
IBW = 50 + (2.3 x inches > 5 ft)

*measured in kg

63
Q

eGFR

A

estimated glomerular filtration rate

normal = >90 mL/min

64
Q

GFR

A

normal = >90

-adjusted based on sex, and if pt is black

65
Q

Modification of Diet in Renal Dysfunction Calculation

A
  • more accurate calculation for excessive body weight and renal dysfunction
  • female, black
  • better for chronic kidney dysfunction, not acute
66
Q

ABW

A

actual body weight

kg

67
Q

Adjusted body weight

A
  • for pts who are over 30% of IBW

- 0.4 (ABW - IBW) + IBW

68
Q

Estimated Creatinine Clearance d/t Dialysis?

A

30 ml/min

69
Q

Dialysis

A
  • removes same shit kidneys do

- unbound, small, ionic

70
Q

Elderly PK changes

A
  • reduced absorption
  • reduced first pass metabolism
  • increased fat %, reduced free water
  • reduced albumin –> increased alpha-1 glycoprotein
  • reduced phase 1 metabolism - CYP450
  • reduced kidney function
  • *increased parent compound in circulation
71
Q

Pediatric PK changes

A
  • higher gastric pH
  • higher water, less fat
  • immature enzymes
  • reduced protein binding
  • reduced renal clearance

BB Pharmacology (3 decks)

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