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Pharmacology 1 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

pharmacokinetics

A

what the body does to the drug, dose-concentration relationship

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2
Q

pharmacodynamics

A

what the drug does to the body, concentration- effect relationship

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3
Q

4 pieces of pharmacokinetics

A

absorption, distribution, metabolism, excretion

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4
Q

why is understanding PK important

A

control therapeutic action of the drug, gives us information about dosage form, route of administration, dose, onset of action, efficacy, side effects, dosing interval

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5
Q

steps in PK

A

dose of drug administered –> drug conc in circulation –> distribution or elimination –> dose concentration at site of action –> pharmacodynamics

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6
Q

AUC

A

area under the curve, total drug absorption over time; increases as drug begins absorbing, decreases when excretion > absorption

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7
Q

Cmax

A

maximum concentration of drug in the blood, peak on the AUC curve, must be in therapeutic range between MTC (max toxicity conc) and MEC (min effective conc)

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8
Q

Vd

A

volume of distribution, Vd= total amount of drug (dose)/conc of drug in plasma; more in blood –> lower Vd

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9
Q

Cl

A

clearance

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10
Q

t1/2

A

elimination half life

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11
Q

Css

A

steady state concentration

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12
Q

factors that affect a drugs movement and availability at sites of action

A

molecular size and structure, degree of ionization, lipid solubility, protein binding

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13
Q

how polarity affects permeability

A

more polar drugs are hydrophilic, harder to get through the membrane

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14
Q

changes in ___ leads to changes of a drug from nonpolar polar

A

pH

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15
Q

absorption

A

transfer of a drug from its site of administration to the bloodstream

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16
Q

oral drugs must ___ to be absorbed

A

dissolve

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17
Q

most drugs dissolve in the ___ and are absorbed in the ___

A

stomach; Small intestines

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18
Q

enteric coated (EC) drugs

A

delayed release drugs, dissolve in small intestines

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19
Q

purpose of enteric coated (EC) drugs

A

to protect the stomach from the drug, to protect the drug from the stomach, to release the drug after the stomach

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20
Q

similarity between delayed release drugs and extended release drugs

A

cannot be chewed, crushed, or dissolved since it will destroy the mechanisms of action; could lead to potential overdose in ER drugs

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21
Q

differences between delayed release and extended release drugs

A

DR: released in small intestines all at once, ER: released immediately in small doses over the course of the day

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22
Q

most drugs are absorbed via ___ transport in the ___

A

passive; small intestines

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23
Q

passive transport of drugs from the instestines

A

go from high conc in the gut to low conc in the plasma (blood), microvilli provide large SA for absorption into bloodstream

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24
Q

factors related to the drug that affect rate and extent of absorption

A

molecular weight, lipid/water solubility, degree of ionization, dosage form, concentration, particle size in tablets

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25
factors related to the body that affect rate and extent of absorption
gastric mobility, intestinal transit time (slow passage --> greater absorption), pH, blood flow to absorption site, SA, food
26
when to take drugs with food
required for absorption (ie high fat), protect stomach, prevent nausea/vomiting, for efficacy
27
when to take drugs without food
required for absorption --> cations (Ca, Fe, Mg, Zn) in food can bind drug and prevent absorption; take 1 hr before or 2-3 after meal
28
p-glycoprotein
efflux pump that pumps drug back into GI lumen, decreases absorption of drug into blood
29
CYP3A4
enzyme that breaks down drug in enterocytes of the SIs, decreased drug absorption
30
first pass effect
first pass metabolism, happens in gut wall enzymes and hepatic enzymes, typical with oral medications, reduces bioavailability; dose gets decreased as is passed through enzymes of the intestines and again in the liver
31
bioavailability (F)
fraction of drug absorbed into systemic circulation after administration
32
absorption of oral drugs
first pass effect may be significant
33
absorption of sublingual drugs
bypasses first pass effect, rapid absorption into oral capillaries
34
absorption of transdermal drugs
bypasses first pass effect, usually slow absorption
35
absorption of rectal drugs
less first pass effect than oral
36
intravenous drug absorption
F=100%, most rapid onset
37
intramuscular drug absorption
depends on injection site and blood flow
38
subcutaneous drug absorption
constant, slow absorption
39
brand name vs generic drugs
generic companies need to prove bioequvalence, inactive ingredients may be different; generic must have same active ingredients, strength, dosage form, route of administration
40
bioequivalence
generic drug has same rate and extent of absorption of a drug
41
distribution
reversible transfer of a drug between compartments, plasma interstitial fluid intracellular fluid
42
compartments
defined volume of body fluids
43
distribution depends on:
molecular size and polarity/lipophilicity of drug
44
where large drug molecules distribute
confined to circulation
45
where polar drugs distribute
excluded by cell membrane from entering intracellular or fatty tissues
46
where lipophilic drugs distribute
in fatty tissues, little in bloodstream
47
factors that affect drug distribution
protein binding, blood brain barrier, storage in tissues
48
protein binding and drug distribution
protein bound portion is not available for action, too big to move out of the blood into the tissues, plasma proteins can act as a transporter of the drug through the blood stream
49
drug competition for plasma proteins
if drug 2 significantly displaced drug 1, drug 1's free concentration increases possibly to a toxic level
50
free drug
drug concentration that is free floating in the blood, not bound to proteins
51
blood brain barrier effect on drugs
prevents distribution of drugs to the brain, tight junctions block many substances, must be small and lipophilic to get through the barrier
52
places where drugs can get stored, how this affects distribution
lipophilic drugs can stay in adipose tissue and wont readily pass back into the blood --> makes treating obese patients difficult, developing teeth or bones can be a storage site for some antibiotics in children <8yo
53
metabolism
biotransformation, chemical alteration of the drug in the body
54
goal of metabolism
to make the drug easier to excrete
55
where most drug metabolism occurs
liver
56
typical pathway of lipophilic drug metabolism
acted on by an enzyme in the liver to become more hydrophilic, sent to the kidneys where it can more easily be excreted
57
2 phases of metabolism
drug --> phase 1 --> active/inactive metabolites --> phase 2--> conjugation products (inactive), do not need both phases for every drug
58
phase 1 of metabolism
oxidation, reduction, hydrolysis; involves CYPP450 enzymes
59
prodrug
requires biotransformation to become active metabolite, usually CYP450 enzymes
60
inhibitors of CYP450
block metabolic activity of CYP enzymes, occurs quickly
61
inducers of CYP450
increase CYP activity by increasing enzyme synthesis, slow process
62
substrate
drug that is metabolized
63
why there is a potential for drug-drug interactions with inducers/inhibitors
one drug may inhibit/induce the metabolism of another which could lead to a potential dose adjustment
64
``` potential clinical impact for an inhibitor drug on CYP450 Drug X (Active)-->Cyp450--> metabolite X (inactive) ```
Drug X concentrations will increase, could lead to possible toxicity (supratherapeutic), would need to decrease the dose of X
65
``` possible clinical impact for an inducer drug on CYP450 Drug X (active) --> CYP450 --> metabolite X (inactive) ```
decreased efficacy, levels of X would be lower, increasing the dose wouldnt always be effective since inducer is signalling CYP450 to continue production of more enzymes
66
importance of knowing OTC medications
OTC drugs and herbal products may cause drug drug interactions, can affect CYP450 effects
67
phase 2 of metabolism
conjugation, addition of a polar molecule
68
purpose of phase 2 of metabolism
add a polar molecule to large compounds that cannot easily move throughout the body so they become polar, easier to be excreted
69
factors that affect rate and extent of metabolism
drug drug interactions, drug food interactions, disease, age, environment, genetics
70
excretion
removal of the drug and its metabolites from the body, mainly in the kidneys
71
processes of the kidneys that allow excretion
glomerular filtration, reabsorption, secretion, excretion
72
glomerular filtration of a drug
depends on plasma protein binding and renal blood flow, capillaries have pores to allow passage into urine, if it is attached to blood proteins it will be too large to pass through the pores, more blood flow --> more filtration
73
clearance
the volume of plasma that is cleared of a drug per unit time
74
glomerular filtration rate
measure of clearance through the kidneys, used to make clinical decisions regarding drug dose and choice
75
renal dosing
drug dose or interval adjustment for decreased kidney function, GFR declines with age and in kidney disease
76
GFR is estimated using ___
creatinine clearance
77
CrCl equation
((140-age) x kg)/ (serum creatinine x 72) x .85 for females
78
normal adult GFR
120 mL/min
79
tubular resorption of drugs
depends on drugs lipid solubility and pH, drug moves from urine tubule back into the blood, easier for lipophilic drugs, hydrophilic drugs continue to be excreted in urine
80
weak acid drugs are excreted faster in ___ urine
alkaline, more RCOO- + H+ --> more ionized and hydrophilic --> readily excreted
81
weak base drugs are excreted faster in ___ urine
acidic, more RNH3+ --> more ionized and hydrophilic --> readily excreted
82
secretion
drug crosses back into urine and is excreted
83
excretion = ___ - ___ + ___
filtration - reabsorption + secretion
84
elimination half life
time required for the plasma concentration of drug to decrease by 50%
85
when T1/2 is useful
when determining dosing interval
86
how poor kidney function affects t1/2
poor kidney function --> takes long time to decrease drug levels --> increased half life
87
steady state plasma concentration (Css)
reached when level being absorbed into the blood = level being excreted, take 4-5 half lives to reach
88
loading dose
give high dose to reach Css faster, lower the dose after to maintain concentration
89
therapeutic drug monitoring
aims to optimize drug treatment by maintaining plasma drug concentration within therapeutic range
90
steps of therapeutic drug monitoring
draw blood --> send to lab --> find blood concentration --> find a dose that is in therapeutic range
91
when therapeutic drug monitoring is used
for drugs with narrow therapeutic range

Pharmacology 1 (4 decks)

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