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Pharmacokinetics Flashcards

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1
Q

definition of drug

A

a chemical entity that affects living protoplasm

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2
Q

definition of medicine

A

a chemical entity used to treat, cure, prevent, or diagnose disease

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3
Q

pharmacology definition

A

study of drugs

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4
Q

how do we achieve goal of drug therapy/medicine?

A

must get adequate amounts of the drug to tissues so that the effect of the drug can be achieved while limiting the toxicity of the drug

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5
Q

pharmacokinetics

A

describes what happens to a drug given to a patient. what the body does to the drug

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6
Q

pharmacodynamics

A

THE BODY’S RESPONSE TO A given drugs. what the drug does to the body

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7
Q

fundamentals of pharmacokinetics

A

AADME (administration, absorption, delivery, metabolism, excretion)

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8
Q

enteral drug administration

A

oral, rectal, sublingual

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9
Q

parenteral drug administration

A

IV, IM, Sub Q

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10
Q

advantages of oral administration

A

ease of use, outpatient care, low cost

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11
Q

disadvantages of oral administration

A

most complicated path and therefore most variable response, first pass effect

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12
Q

first pass effect

A

the concentration of a drug is greatly reduced before it reaches the systemic circulation (hepatic vein to IVC). It is the fraction of lost drug during the process of absorption which is generally related to the liver and gut wall

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13
Q

enteropathic circulation

A

instead of taking portal vein to liver, some drugs are recycled back and forth within GI

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14
Q

advantages of rectal administration

A

relative ease of use, outpatient care, low cost, no pH/food effects, tolerability

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15
Q

disadvantages of rectal administration

A

(less) complicated path/variable response. (less) first pass effect

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16
Q

advantages of sublingual administration

A

ease of use, outpatient care, *rapid onset of action (direct systemic absorption), bypasses stomach/intestine, *no first pass effect

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17
Q

disadvantages of sublingual administration

A

expensive, taste, limited available formulations

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18
Q

advantages of IV (IA) administration

A

bypasses stomach/intestine, no first pass effect, precise control of dose, rapid onset of action

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19
Q

disadvantages of IV (IA) administration

A

invasive (IA especially painful), expensive, unintentional overdosing, inpatient/supervised

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20
Q

advantages of IM/Sub Q administration

A

bypasses stomach/liver, aqueous solution=fast onset of action, non-aqueous solution=slow sustained response

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21
Q

disadvantages of IM/Sub Q administration

A

invasive, expensive, requires absorption, supervised, impossible to remove

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22
Q

transdermal administration

A

skin acts as rich absorptive SA, bypasses first effect, improved compliance, lipid solubility determines absorption

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23
Q

topical drug delivery

A

delivering drug directly to site of needed action

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24
Q

administration via inhalation

A

rapid delivery over large SA of respiratory tract, lung parenchyma is permeable to peptides, lower metabolism in lung tissue, molecular size must be small

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25
absorption definition
transfer of drug from the site of administration to systemic circulation
26
which type of administration has complete absorption?
IV (100%)
27
what does GI absorption depend upon?
blood supply, presence of food in stomach, presence of other meds in stomach, level of enterocyte metabolism, disease states, permeation principles, effect of pH
28
permeation principles
passive diffusion, lipid diffusion, special carriers, endo/exocytosis
29
ticks law of diffusion
movement from high to low areas of concentration
30
how do water soluble drugs penetrate membrane via diffusion?
through aqueous channels. increased size diminishes absorption
31
how of lipid soluble drugs penetrate membrane via diffusion?
through the membrane. size isn't an issue, but charge is
32
henderson hasselbach principle for lipid diffusion
tells what proportion of drug will be in uncharged state at any given pH. easier for uncharged to pass membrane so most drugs are weak acids/bases
33
where do weak acids vs bases generally get absorbed?
acids: stomach bases: intestine
34
carrier mediated absorption
energy dependent process requiring ATP. moves drugs against concentration gradient, saturable
35
bioavailability
the efficiency of absorption. fraction of the administered drug that reaches the systemic circulation in an UNCHARGED form
36
calculate bioavailability
area under curve for administration/area under curve for IV
37
how does first effect affect bioavailability
reduces it since amount actually absorbed in systemic circulation is decreased by gut enterocytes and liver
38
definition of distribution
process by which a drug REVERSIBLY leaves the blood stream and enters the interstitial and/or cells of a tissue
39
what happens once a drug distributes?
enters one of three compartments or is sequestered
40
where are drugs most commonly sequestered?
bone and adipose tissue (fetus if pregnant)
41
three compartments a drug can distribute into
plasma, interstitial fluid, intracellular fluid
42
ECF
plasma + interstitial fluid
43
total body water
plasma + IF + ICF =42L
44
what determines where a drug distributes?
blood flow, capillary permeability, hydrophobicity/lipophilicity of drug, binding to plasma proteins
45
blood brain barrier
brain capillary endothelial cells are continuous via tight junctions and prevent substances from entering interstitium
46
role of plasma proteins
sequester drugs in a nondiffusible form in the plasma. drugs bound to them are inactive, binding is reversible though.
47
volume of distribution
a hypothetical volume of fluid into which a drug is disseminated prior to elimination. (bioavailable dose)/(concentration in plasma)
48
small Vd after drug is displaced from plasma protein binding site...
concentration in plasma is high=increased risk of toxicity
49
large Vd after drug is displaced from plasma protein binding site...
drug can distribute into other compartments and risk of toxicity is low
50
value of Vd if drug is distributed throughout total body water
0.6 L/Kg
51
Large Vd tells drug is distributed...
throughout entire body (water soluble, easily distributed, small molecule)
52
Small Vd tells drug is distributed...
within plasma.
53
drugs only distributed in plasma
large molecular weight or binds tightly to plasma proteins, too big to pass into IF or not free to do so
54
drugs distributed to ECF
low molecular weight, hydrophilic, can move through endothelial slit junctions into IF.
55
drugs distributed throughout total body water
drug has low molecular weight, lipophilic, can move through cell membrane and slit junctions, distribute into huge volume, water soluble
56
drugs distributed to tissues
drug bound receptors or carrier mechanism, drug sequestered in bone or fat tissue
57
elimination
metabolism + excretion
58
metabolism/biotransformation primary purpose
inactivate drug. achieved by converting drug into more excitable form (polar compound)
59
prodrugs
require biotransformation to become activated
60
where does the majority of drug metabolism take place?
liver (but really any cell with mitochondria)
61
phase 1 drug metabolism
oxidation via cytochrom P450. primary mode of metabolism, difficult to saturate
62
phase 2 drug metabolism (not always sequential)
couples endogenous substrate to a drug or to its phase 1 metabolite. CONJUGATION. (acetylation, methylation, etc)
63
CYP
cytochrome P-450 system. major catalyst of drug and endogenous compound oxidations
64
most common CYP families
1,2,3
65
which specific CYP protein is responsible for many drug metabolisms
CYP3A4
66
rifampin
drug used in treatment of TB. side effect=orange fluid. increases activity of CYP3A4, therefore decreasing the efficacy of drugs dependent on phase 1 (breaks them down quicker, St Johns Wort too)
67
grapefruit juice
decreases activity of CYP3A4 in GI endothelial cells, thereby increasing timespan/concentration of dependent drugs
68
polymorphisms in CYP family genes
increased copies of genes leads to faster metabolism of dependent drugs (CYP2D6 example)
69
consequence of reduced metabolism
toxicity, death
70
consequence of increased metabolism
loss of efficacy
71
inhibition of gastric endothelial cell CYP3A4 activity results in...
increased absorption of orally administered drugs
72
enterohepatic circulation
biliary excretion
73
functional unit of the kidney
nephron
74
three processes of renal excretion
glomerular filtration, active tubular secretion, passive tubular reabsorption
75
amount of drug excreted by the kidney
the sum of the amount filtered and secreted minus the amount reabsorbed
76
elimination
metabolism & excretion. the process whereby the body terminates drug action
77
what is the rate of elimination called?
clearance
78
what is clearance proportional to?
concentration of the drug
79
first order kinetics
when clearance is DIRECTLY proportional to the concentration of the drug
80
zero order kinetics
capacity limited excretion, elimination is saturable.
81
kinetics at low drug concentrations
first order
82
kinetics at high drug concentrations
zero order (saturable)
83
half life of drug
the time required to eliminate half of the amount of drug in the body or to reduce the plasma concentration by 50%
84
how is half life of drug calculated?
from the plasma concentration curve following administration of a single dose of the drug
85
how many half lives for first order kinetics to eliminate >90% of drug?
4
86
steady state concentration
when rate of accumulation is equal to the rate of elimination
87
how long does it take to reach steady state?
4-5 half lives (think inverse of elimination: i.e. how long to reach >90%/plateau)
88
what is the steady state concentration directly proportional to?
drug dose administered per unit of time and the elimination half life
89
will a drug administered by continuous infusion reach steady state at different time than drug administered intermittently?
no, they will both reach it at the same time, but intermittent drug plasma level will just flucuate
90
loading dose
a dose that saturates. used when it is necessary to rapidly achieve a therapeutic plasma concentration. commonly used with antibiotics and anticoagulants
91
maintenance dose
given to establish or maintain a desired steady state concentration
92
impact of liver disease on pharmacokinetics
reduced phase 1 metabolism and reduced albumin
93
impact of renal failure on pharmacokinetics
reduced GFR and secretion
94
impact of heart failure on pharmacokinetics
volume expansion, reduced circulation

MDTI (42 decks)

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