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Pharmacology test 1 > Uptake and Distribution of IV agents > Flashcards

Uptake and Distribution of IV agents Flashcards

1
Q

Pharmacokinetic

A

what the body does to a drug

-absorption -distribution -metabolism -excretion

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2
Q

Volume of Distrubution

A

the volume in which the drug has effect before elimination
the drug moving from the central compartment to the peripheral
VD= drug given/ serum [ ]

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3
Q

Central compartment

A

highly perfused tissue
kidney, liver, lungs, heart, brain
receives 75% CO
represents only 10% of body mass

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4
Q

Peripheral compartment, what happens with age?

A

large calculated volume
extensive uptake of drug
?less well-perfused ex muscle, fat?
rate of transfer btwn compartments decrease with age—leading to greater plasma concentration in certain drugs

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5
Q

Distribution, how it happens

A
  • drug has systemic absorption then
  • drug goes to central compartment and the plasma concentration decrease
  • drug enters peripheral then
  • with continued elimination the drug plasma concentration decreased below the tissue concentration and the drug re-enters the plasma from the tissue
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6
Q

large dose or repeated doses

A

saturate inactive tissue preventing redistribution

  • prolonging duration of action
  • reduction of effect now depends on metabolism rather than redistribution
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7
Q

lung uptake

A

basic lipophilic drugs

acts as a reservoir to release drug back into the systemic circulation

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8
Q

blood brain barrier

A

prevents ionized, water soluble drugs from crossing

-can be overcome by large dose, head injury, and hypoxemia

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9
Q

Vd is influenced by: 3 physiochemical characteristics

A
  1. Lipid solubility- increase lipiophylic increase vd
  2. Binding to plasma protein– more binding less vd
  3. Molecular size–bigger less vd
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10
Q

Elimination Half-Time and its relationships

A

time needed for plasma [ ] of drug to decreased by 50%

  • directly proportional to vd
  • inversely to clearance
  • independent pf drug dose
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11
Q

Elimination Half-Life, fully eliminated when? Drug accumulation when?

A

time needed to eliminate 50% of drug from body

  • regarded as fully eliminated when approximately 98%? has been eliminated or 6 half lifes
  • drug accumulation occurs if dosing intervals are less than 4-5 half lifes
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12
Q

absorption oral

A

most convenient and economic

disadvantages:
- many conditions can change GI environment therefore lower bioavailability
- destruction by enzymes or acidic gastric fluid
- first pass effect

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13
Q

first pass effect

A

hepatic effect

  • drugs absorbed in GI tract enter the portal venous blood and pass through the liver first
  • liver metabolized drug before enter systemic circulation
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14
Q

sublingual absorption

A

rapid onset

bypass liver prevents first pass effect

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15
Q

transdermal

A

provided sustained therapeutic plasma [ ]

  • water soluble: penetrate hair follicles and sweat ducts
  • lipid soluble: once in system transfers skin
  • rate-limiting step–diffusing across stratum corneum of epidermis
  • should apply to thing epidermis with sufficient blood supply
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16
Q

rectal absorption

A

proximal rectum–transported to portal system via superior hemorrhoidal veins—first pass
-distal rectum-bypass portal system, more predictable circulatory level

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17
Q

IV absorption

A

achieve therapeutic plasma levels precisely and rapidly

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18
Q

Ionization

A
  • most drugs are salts of either weak acids or weak bases

- present in both ionized (charged, water soluble) and Nonionized (uncharged, lipophilic)

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19
Q

Nonionized

A

Lipophilic, can diffused across cell membrane

ex: BBB, renal tubules, GI epithelium, hepatocytes, placenta
* pharm active
- absorbed from GI tract, metabolized by liver, reabsorbed across renal tubes

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20
Q

Ionized

A

poorly lipid soluble

  • cannot penetrate lipid cell membrane
  • is repelled by portions of the cell with similar charge
  • excreted by kidneys unchanged
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21
Q

Degree of Ionization

A

the higher the degree of ionization the less access the drug has to diffuse across tissue

  • depends of the pKa of the drug and in pH of the surrounding fluid
  • when pH=pKa 50% of the drug is ionized
22
Q

More Nonionized

A

weak base pH>pKa

weak acid pH<pKa

23
Q

More ionized

A

weak base pHpKa

24
Q

Ion trapping

A

[ ] difference of a drug/degree of ionization of drug can develop on either side of a membrane that separates fluids with different pHs
ex: placenta, fetus more Acidic, basic drug can cross membrane buy once on fetus side becomes ionized can cross back over, accumulates in fetus

25
Q

Protein binding: what proteins, VD, drugs effected

A

most drugs bind to plasma proteins in various degrees
Proteins: albumin
-a, acid glycoprotein-bases lipoproteins
**only free or unbound fraction of drug is easily and readily available to cross cell membrane and is metabolized, excreted more readily too.
-protein bound-too lg to cross membranes–trapped in circulation
**VD is inversely proportional to protein binding
**high protein bound: Warfarin, Propranolol, Phenytoin, Diazepam

26
Q

Clearance

A

Volume of plasma cleared of drug by metabolism and excretion per unit of time

27
Q

First-order kinetics

A

drugs administer in the THERAPUTIC dose ranges are cleared at a rate PROPORTIONAL to the amount to drug in the plasma (1/2 life thing)
-constant FRACTION of drug eliminated per unit of time

28
Q

Zero-order kinetics

A

drugs that exceed the metabolic or excretory capacity of the body to clear drugs

  • dose doesn’t make a difference
  • CONSTANT amount of drug is cleared per unit of time
  • ex: ASA, ETOH, Dilantin
29
Q

Hepatic clearance: ratio, 2 different types

A

ratio btwn hepatic blood Flow and hepatic Extraction

  • if ratio is high >0.7 clearance depends on blood flow **perfusion dependent elimination
  • if ratio is low <0.3 clearance depends on protein binding and enzyme activity and blood flow will have minimal effects (decreased pb or increase e to increased clearance) ** Capacity- dependent (enzyme-dependent)
30
Q

Renal Clearance

A

most important organ for the elimination of unchanged drugs or their metabolites

  • Water soluble compounds are excreted more efficiently
  • highly lipid soluble drugs are reabsorbed such that little or no unchanged drug is excreted in urine
31
Q

Metabolism: does what where, why

A

biotransformation to convert pharm Active LIPID soluble drugs to WATER soluble often Inactive drugs

  • liver is the main site with enzymes to break down drugs
  • some drugs have active metabolites
  • *metabolism is not always synonymous with Inactivation -some metabolites of certain drugs are active.
32
Q

Increased water solubility in a drug therefore….

A

Decreased VD and Increased Renal excretion

33
Q

Pathways of metabolism 4

A
  1. Oxidation 2. Reduction 3. Hydrolysis 4. Conjugation
34
Q

Phase 1 reactions

A

Oxidation: oxygen is introduced into molecule, lose electron
Reduction: gain of electron
(Oil Rig)
Hydrolysis: addition of water to an ester or amide to break the bond and form 2 smaller molecule, do not include CP450 and is often outside the liver
**phase 1 reactions: increased the drugs polarity and prepares it for phase 2

35
Q

Phase 2 reactions

A

Conjugation: covalently links the drug or metabolite with a highly polar molecule rendering it Water soluble

  • synthetic reaction
    sites: plasma, kidneys, lungs, GI tract, liver
  • *hepatic microsomal enzymes are responsible for metabolism of most drugs
36
Q

hepatic microsomal enzymes

A

located in hepatic smooth ER

  • Cytochrome P-450
  • large number of different protein enzymes involved in Oxidation and Reduction and Conjugation of lg # of drugs
37
Q

Enzyme induction

A

drugs and chemicals stimulates activity of these enzymes

*burn through drugs quickly

38
Q

Nonmicrosomal enzyme

A

metabolize drugs mostly by conjugation and hydrolysis

  • to lesser degree-also redox
  • mostly in plasma, GI also in: liver
  • responsible for hydrolysis of drugs that contain ester bonds (succs, esmolol)
39
Q

pharmacodynamics

A

what a drug does to the body

  • mechanism of effect
  • sensitivity
  • responsiveness
  • most common mechanism–interaction with Receptors
40
Q

Concentration of Receptors

A

up-reguate or down-regulate

in response to specific stimuli

41
Q

non receptor drug action

A

-not at common
-mechanisms of other that receptor-drug interaction
ex Chelating drugs form bonds with metallic cations that may be found in body
-antacids neutralize gastric acids by a direct action

42
Q

Agonist drug

A

mimic cell signaling, activating, causing similar effects

43
Q

Antagonist drug

A

bind to receptor, prevent agonist from binding, prevent effect

44
Q

Structure-activity

A

affinity of a drug for a specific receptor and its intrinsic activity are intimately related to CHEMICAL STRUCTURE!
-subtle change such as stereochemistry can result in a major change in pharmacological properties

45
Q

Stereochemistry

A

enantiomers: stereoisomers that are non-superimposable mirror images of each other
- chiral centers-carbon with 4 different asymmetric substituents–1 chiral carbon has 2 stereoisomer
* *interaction with biological recptors can differ greatly btwn 2 enantiomer to the point of no binder
* *some isomers may cause side effects or entirely different effects than its mirror image.

46
Q

Efficacy

A

ability of a drug to produce desired therapeutic effects

47
Q

potency

A

relationship btwn therapeutic effect of drug and dose necessary to achieve effect

48
Q

ED50 vs LD50

therapeutic index

A

ed-mean effective dose
ld-mean lethal dose
-ratio btwn the 2 indicates the therapeutic index of the drug for that effect.
-suggest how selective the drug is in producing its desired effects
-estimates the clinical therapeutic index **shorter is WORSE

49
Q

Hyper-reactive

A

low dose produces its expected pharm effect

50
Q

hypersensitivity

A

allergic

51
Q

Additive effect

A

2nd drug acting with 1st produce effect = to sum of both 1+1=2

52
Q

Synergetic effect

A

2nd drug acting with 1st produce effect Greater than their sum 1+1=3

Pharmacology test 1 (4 decks)

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