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Pharmacology- NURA 661 > Uptake and Distribution of IV Agents > Flashcards

Uptake and Distribution of IV Agents Flashcards

1
Q

synergetic effect

A
  • two drugs interact to produce an effect greater than their sum
    • 1+1 = 3
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2
Q

potency

A
  • how strong the drug is.
  • the dose necessary to achieve therapeutic effect
    • ex. hormones
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3
Q

Pharmacokinetics

A
  • what the body does to the drug
    • absorption
    • distribution
    • metabolism
    • excretion
  • Commonly measured:
    • elimination half-time
    • bioavailability
    • clearance
    • volume of distribution
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4
Q

bases bind to:

A

alpha acid glycoprotein

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5
Q

enzyme induction

A
  • drugs and chemicals stimulate activity of the hepatic microsomal enzymes
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6
Q

acids bind to:

A

albumin

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7
Q

Clearance

A
  • volume of plasma cleared of drug by metabolism and excretion
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8
Q

Hepatic clearance

A
  • equals the hepatic blood flow and hepatic extraction ratio.
  • if hepatic extraction for a drug is high (>0.7) the clearance will depend on hepatic blood flow.
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9
Q

Peripheral compartment

A
  • large calculated volume
  • extensive uptake of drug

**Rate of transfer between compartments decreases with aging, leading to greater plasma concentration in certain drugs

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10
Q

additive effect

A
  • second drug acting with the first will produce effect equal to the sum of both
  • 1+1 = 2
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11
Q

Non-ionized

A
  • usually lipid soluble and can diffuse across lipid cell membranes
    • BBB
    • renal
    • tubules
    • GI epithelium
    • hepatocytes
  • pharmacologically active
    • gets re-absorbed across renal tubules, is absorbed from GI tract and is metabolized by the liver
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12
Q

rectal

A
  • proximal rectum transports to the portal system via superior hemorrhoidal veins
    • therefore experiences first-pass effect
  • distal rectum bypasses portal system

**this is why rectal administration provides unpredictable responses.

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13
Q

Distribution

A
  • after systemic absorption of drug, the highly perfused tissues (heart, brain, kidneys, liver) receive a large amt of drug.
  • as plasma level of drug decreases below these tissues, drug leaves and is redistributed to less well perfused sites (muscle, fat)
  • plasma level decreases below these sites (muscle and fat) and drug leaves tissue to reenter circulation
  • tissues that accumulate drug act as reservoir and prolong effect
  • large or repeated doses saturate inactive tissue negating redistribution and prolonging action
    • b/c now reduction of effect depends on metabolism instead of redistribution
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14
Q

Renal clearance

A
  • water soluble compounds are excreted more efficiently than lipid soluble drugs
  • highly lipid soluble drugs are reabsorbed so little or no unchanged drug is excreted in urine
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15
Q

Lung uptake

A
  • lung uptakes basic lipophilic drugs and acts as a reservoir to release drug back into the systemic circulation
    • lidocaine
    • fentanyl
    • demeol
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16
Q

IV

A
  • achieve therapeutic plasma levels precisely and rapidly
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17
Q

First-pass effect re oral administration

A
  • drugs absorbed from GI system enter the portal venous blood and pass through the liver before entering the systemic circulation for delivery to tissue receptors
    • in GI system they are extensively extracted and metabolized.
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18
Q

Effect site

A
  • drugs exert their biological effect at the “biophase”
    • biophase aka “effect site”
  • the place where the drug acts upon the body
    • membranes
    • receptors
    • enzymes
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19
Q

First-Order Kinetics

A
  • almost all drugs administered in the therapeutic dose ranges are cleared at a rate proportional to the amount of drug in plasma
    • (Think about this like the enzyme chart when there are more enzymes than substrate)
  • most common
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20
Q

phase 2 metabolism

A
  • covalently links drug or metabolite with highly polar molecule, making a more water soluble conjugate
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21
Q

oxidation

A

losing an electron

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22
Q

Ion trapping

A
  • concentration difference of total drug can develop on two sides of a membrane that separates fluids with different pHs
    • ex: placenta
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23
Q

Protein binding

A
  • most drugs bind to plasma proteins
  • only free or unbound fraction of drug is easily and readily available to cross cell membranes
    • Vd is inversely proportional to protein binding
  • proteins are:
    • albumin
    • alpha acid glycoprotein
    • lipoproteins
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24
Q

Ionized drugs

A
  • poorly lipid soluble
  • can not penetrate lipid cell membranes
  • repelled from portions of the cell with similar changes
  • excreted by the kidneys unchanged
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25
Q

nonmicrosomal enzymes

A
  • metabolize drugs mostly by conjugation and hydrolysis
    • some oxidation and reduction too
  • present in liver, plasma, GI tract
  • responsible for hydrolysis of drugs that contain ester bonds
    • succhs, esmolol
  • some people dont have them, which cannot be affected by enzyme induction
    • determined genetically
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26
Q

Vd influenced by:

A
  • Volume of distribution
  • influenced by the physiochemical characteristics of the drug:
    • lipid solubility
    • binding to plasma proteins
    • molecular size
27
Q

antagonist drugs

A
  • bind to receptors and change the configuration of the agonist site or bind to it, preventing effect from cell signaling molecules
28
Q

transdermal

A
  • provides sustained therapeutic plasma [] of drug
  • absorption occurs along sweat ducts and hair follicles that function as diffusion shunts
  • rate-limiting step is diffusion across the stratum corneum of the epidermis (thick part of skin)
  • thickness and blood flow are factors reflected in the skin’s permeability for drugs
  • contact dermatitis can occur at the site.
29
Q

enantiomer

A
  • two stable forms of a molecule slightly differently shaped.
    • interaction with receptors can differ greatly
30
Q

Volume of distribution

A
  • sum of the volumes of the compartments
  • Vd = dose of IV drug/Plasma [] before elimination
31
Q

Sites of metabolism

A
  1. plasma (adenosine, esmolol)
  2. kidneys
  3. lungs
  4. GI tract
  5. liver
32
Q

hyper-reactive

A
  • people who have desired effect of drug from an unusually low dose
33
Q

how do drugs exert effects without using receptors?

A
  • antacids neutralize gastric acid by a direct action
    • adding a base to an acid to form a salt
34
Q

Ionization

A
  • most drugs are weak acids or bases
  • can be ionized and non-ionized
35
Q

context sensitive half time

A
  • the time required for plasma concentrations of a drug to decrease by 50% after discontinuation of drug administration
    • in reference to discontinuation of an infusion
    • depends on:
      • distribution
      • excretion
      • physiochemical properties of the drug
      • length of infusion
36
Q

Compartmental models

A
  • divides the body into compartments that represent theoretical spaces with calculated volumes
    • 2 compartments:
      • central
      • peripheral
37
Q

hydrolysis

A

water added to substance causes chemical reaction

38
Q

metabolism

A
  • transforms the drugs to make them water soluble and (often) inactive drugs
  • increased water solubility reduces the Vd for a drug and enhances its renal excretion
  • metabolism is not aways synonymous with inactivation or detoxification as some metabolites of certain drugs are active. (metabolite of versed)
39
Q

zero order kinetics

A
  • constant amount of drug is cleard per unit of time because the drug will exceed the metabolic or excretory capacity even at therapeutic doses
    • ex: aspirin, dilantin, ETOH
40
Q

phase 1 of metabolism

A
  • oxidation, reduction, hydrolysis
41
Q

efficacy

A
  • the ability of a drug to produce the desired effect
42
Q

elimination half time

A
  • time necessary for the plasma [] of drug to decline 50% during the elimination phase
  • directly proportional to its Vd and inversely proportional to its clearance
  • elimination half time is independent of the dose of drug administered.
43
Q

absorption

A
  • systemic absorption depends on the drug’s solubility
    • no matter how it is administered
44
Q

hepatic microsomal enzymes

A
  • located in hepatic smooth ER
  • cytochrome P-450: large amount of different protein enzymes involved in oxidation and reduction and conjugation of a large number of drugs
    • (enzymes in the liver)
45
Q

state of receptor activation theory

A
  • non-activated receptors are converted to active by the drug
46
Q

pathways of metabolism

A
  1. oxidation
  2. reduction
  3. hydrolysis
  4. conjugation
47
Q

perfusion dependent elimination

A
  • if the hepatic extraction for a drug is high (>0.7) the clearance of the drug will depend on hepatic blood flow
48
Q

Ke0

A
  • the rate constant of drug elimination from the effect site
49
Q

oral administration advantages vs disadvantages

A
  • advantages
    • most convenient
    • most economic
  • disadvantages
    • emesis
    • destruction by enzymes or acidic gastric fluid
    • irregular absorption with food or other drugs
50
Q

Degree of ionization

A
  • depends on its dissociation constant (pK) and the Ph of the surrounding fluid
  • changes in pH can result in large degree of ionization
    • i.e. acidic drugs are highly ionized at alkaline pH and vice versa
      • giving an acidic med to an acidic pt requires less drug b/c there will be less ionized
51
Q

Central compartment

A
  • highly perfused tissues
  • rapid uptake of drug
  • drug first introduced into the central compartment distributes to the 2nd compartment and returns to central compartment for clearance
    • kindney, liver, lungs, heart, brain
    • receives 75% of CO
    • represents only 10% of the body mass
52
Q

ED 50 vs LD 50

A
  • ED 50: median effective dose
  • LD 50: median lethal dose
  • ratio of LD 50 and ED 50 indicates the therapeutic indes of a drug
53
Q

Pharmacodynamics

A
  • What a drug does to the body
  • mechanism of effect
  • sensitivity
  • responsiveness
54
Q

receptor occupancy theory

A
  • the more receptors occupied by drug the more effect
55
Q

elimination half life

A
  • time necessary to eliminate 50% of the drug from the body
  • drug accumulation occurs if dosing intervals are ess than the elimination half times
  • elimination half-time and elimination half-life are not equal when the decrease in the drug’s plasma [] does not parallel its elimination from the body.
56
Q

hypersensitivity

A
  • allergy to drug
57
Q

how do drugs exert effects?

A
  • interaction with specific macromolecules in the lipid bi-layer of cell membranes called receptors
    • can increase or decrease in number in response to specific stimuli
58
Q

Sublingual, transmucosal

A
  • rapid onset
    • bypasses liver and prevents first pass effect
59
Q

reduction

A

gaining an electron

60
Q

CNS distribution

A
  • blood-brain barrier (BBB) prevents ionized, water soluble drugs from crossing the barrier into the brain circulation
  • BBB can be overcome with large doses of drug, in head injury, and hypoxemia
61
Q

Capacity dependent elimination

A
  • if hepatic exraction ratio is low (<0.3) a decrease in protein binding or an increase in enzyme activity will increase hepatic clearance
  • changes in hepatic blood flow will have minimal changes in its clearance
62
Q

agonist drugs

A
  • mimic cell signaling molecules by activating the same receptor sites and causing similar effects
63
Q

Therapeutic index

A

LD50/ED50

64
Q

Steady state plasma concentration of drug

equation

A

steady state plasma concentration of drug =

dose rate/clearance

Pharmacology- NURA 661 (5 decks)

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