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BECOM II Exam 5 > Lee - Pharmacokinetics > Flashcards

Lee - Pharmacokinetics Flashcards

1
Q

pharmacokinetics

A

what body does to drug

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2
Q

pharmacodynamics

A

what drug does to body

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3
Q

pharmacogenetics

A

influence of one gene on drug

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4
Q

pharmacogenomics

A

influence of entire genome on drug

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5
Q

what are 2 ways to get toxic effects?

A

drugs going to unintended targets or overdose of therapeutic drugs

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6
Q

spermeation

A

movement through or around cells which limit size

-drugs have to be of certain size and shape to be absorbed and bind to certain receptors

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7
Q

efficacy

A

effect of drugs

  • same effect b/w 2 drugs –> same efficacy
  • nothing to do with []
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8
Q

potency

A

amount of drug to get an effect

-least concentration –> most potent

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9
Q

what is the best type of drug to give?

A

one with least potency and takes a higher dose to have effect
-easier to manipulate and regulate

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10
Q

steps in pharmacokinetics

A
  1. absorption
  2. distribution
  3. metabolism
  4. excretion
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11
Q

absorption

A
  • polar molecules more easily absorbed (biotransformation in liver)
  • no rxn with receptor if bound to carrier
  • tight junctions (fast), lipophilic, facilitated or active transport, or endo/exocytosis (slow)
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12
Q

distribution

A

volume of distribution = amount of drug in body relative to [] in blood - measure space available to house the drug

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13
Q

metabolism

A

biotransformation by the liver - more polar and water soluble through conjugation to be excreted in urine

  • phase 1 and 2 enzymes
  • some drugs not metabolized
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14
Q

excretion

A
  • elimination - rate of removal from circulation

- clearance - body’s ability in removing drug

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15
Q

agonist

A

bind to same site as ligand to have same effect

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16
Q

antagonist

A
  • competitive - binding to same site to block ligand (no response)
  • non-competitive - bind to other site to elicit effect
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17
Q

allosteric activator vs. inhibitor

A
  • activator - bind to other receptor site increasing receptor response
  • inhibitor - bind to other site decreasing response
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18
Q

partial agonist

A

sometimes called antagonist

  • agonist on its own
  • antagonist in presence of other substrate
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19
Q

therapeutic index

A

Toxic/lethal does divided by effective dose

-bigger number –> better drug

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20
Q

tolerance

A

down regulating receptors after therapeutic effect takes place

  • decrease receptor –> decrease effect
  • may have to increase dose
  • protective response
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21
Q

barriers to absorption

A
  • cell membrane - small (paracellular; lipophilic (diffuse); hydrophilic and charged (transporter)
  • capillaries - easier to get drugs across (larger pores)
  • blood/brain - protection; need transporter
  • placenta - only lipophilic drugs across
22
Q

1st pass metabolism

A

oral –> GI –> hepatic portal vein –> metabolized by liver (protection)

  • occurs before interacting with receptor
  • can decrease availability in circulation and less reaches active site
  • skip by using another method besides oral
  • bioavailability good indication
  • proteins and lipids have high 1st pass - do not take orally
23
Q

bioavailability

A

% of drug that ends up in circulation after 1st pass metabolism
-IV (most) > transdermal > IM and subQ > rectal > oral and inhalation

24
Q

large, polar, lipophilic drug

A

do not take orally

  • take IV or IM
  • harder to be absorbed, 1st pass metabolism, more broken down
25
Q

non polar, uncharged drugs

A

more easily absorbed - take orally

26
Q

henderson-hasselbach equation

A

pH = pKa + log10 ([A]/[HA])

  • uncharged molecules better absorbed than charged
  • more acidic –> more uncharged
  • more basic –> more charged
  • equal charged and uncharged when pH = pKa
27
Q

ion trapping

A
  • gastric juice (pH 2) –> convert to uncharged form –> better absorption
  • plasma (pH 7) –> reconvert to charged form –> ion trapping
  • ex. aspirin being absorbed in stomach
  • ex. methamphetamine in urine - can change pH of urine to excrete faster
28
Q

drug bound to protein

A

cannot exit to peripheral tissues or bind to receptor

  • acts as reservoir
  • drug maintained in central compartment
  • liver damage –> less albumin –> more free drug and higher effect
29
Q

lipophilic/fat soluble drugs

A

bypass 1st pass metabolism bc they enter lymphatic circulation then head to periphery 1st
-end up in adipose tissue compartment

30
Q

partition coefficient

A

ratio of solubility of a substance in water to a lipophilic, non-polar solvent

  • determine how hydrophilic/hydrophobic something is
  • larger number –> more hydrophobic
31
Q

volume of distribution

A

measure of space in body to contain drug
Vd = amount of drug/plasma []
-low # –> drug in central compartment
-high # –> drug in peripheral compartment and has longer half life (not metabolized or excreted)

32
Q

one vs. two compartment model

A

administer drug –> central –> peripheral –> metabolized and excreted by liver and kidneys in central increasing [] in peripheral (reservoir) –> drug reenters central to reach equilibrium

33
Q

what is the goal of phase 1 and 2 rxns

A

make something more polar –> better excretion

  • CYP enzymes in liver (can activate or deactivate drug)
  • phase 1 = oxidize
  • phase 2 = conjugate
34
Q

CYP enzymes

A

needed by phase 1 rxns

  • lipophilic, mainly in the ER membranes, Low specificity and react with a lot of molecules breaking them down
  • can inactivate a drug or activate a prodrug
35
Q

phase 2 rxns

A

conjugation

  • not CYP dependent
  • make more water soluble than phase 1
  • oxidative stress can decrease GSH levels
36
Q

what can hydrolysis during phase 1 lead to?

A

toxicity of drug - best to excrete it before reaching phase 1

37
Q

acetaminophen

A

broken down into metabolite –> excreted by GSH or other conjugators or go down toxic path

  • excess acetominophen –> induce CYP2E1 –> toxic pathway
  • EtOH also induces CYP2E1 –> immediate toxicity
38
Q

CYP3A/4

A

metabolize 50% of drugs in phase 1

39
Q

glucoronidation

A

metabolize 25% of drugs in phase 2

40
Q

competitive inhibition of drugs

A

reduce metabolism when 2 drugs competing for the same site

  • prodrug not metabolized fast enough to have effect
  • real drug not broken down into inactive –> toxic
  • can be substrate and inhibitor at same time
41
Q

inducers vs. inhibitors

A

inducers - increase CYP enzyme and metabolism
-ex. rifampin, carbamazepine, ethanol
inhibitors - downregurate CYP decreasing activity
-ex. erythromycin, grapefruit, cimetidine

42
Q

elimination vs. excretion

A 
elimination = remove drug by excretion or or biotransformation (drug --> metabolite) 
excretion = removal of intact drug
43
Q

ion trapping

A

pH changes across 2 different tissues that traps an ion in one of the tissues

  • weak acid - uncharged if pH below pKa –> can get across
  • weak base - charged if pH is above pKa –> cannot get across (trapped)
44
Q

enterohepatic circulation

A

where lipophilic drugs end up

  • another compartment, not much enter circulation
  • reservoir for lipophilic drugs that can leak back into circulation causing effect
45
Q

clearance

A

ability of organs to eliminate drug from the body

-region of body that is cleared of a drug

46
Q

half life (t1/2)

A

time required to reduce the drug in the body by half during elimination

47
Q

zero order rxn

A
  • elimination rate CONSTANT - not dependent on drug []
  • half life CHANGES - longer half-life with more drug
  • linear
  • ex. PEA (phenytoin, ethanol, aspirin)
48
Q

1st order rxn

A
  • elimination rate dependent on drug [] –> faster with more drug
  • half life CONSTANT
  • exponential
  • 95% of drug eliminated in 5 half lives
49
Q

impact of infusion and bioavailability

A
  • increase infusion rate –> increase []
  • equal infusion but half bioavailability –> lower [] but longer duration
  • half infusion rate, same bioavailability –> decrease [] and duration
50
Q

maintenance dose rate

A

plasma drug concentration x clearance x time divided by bioavailability
-maintain dose in plasma - keep at equilibrium

51
Q

loading dose

A

plasma drug concentration x Vd divided by bioavailability

-given to overcome lag period

52
Q

half life equation

A

0.7 x Vd divided by CL

BECOM II Exam 5 (24 decks)

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