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Pharm & Ototoxicity > Principles of Pharmacokinetics > Flashcards

Principles of Pharmacokinetics Flashcards

(101 cards)

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1
Q

Any proposed pharmacological therapy, no matter how promising, will fail in clinical trials if

A

the ddrug is unable to reach its target organ(s)
at concentrations sufficient to have a therapeutic effect

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2
Q

what makes a drug successful

A

A successful drug must be able to cross the same physiologic barriers that exist in the body to limit access to foreign substances (e.g., virus, bacteria, and environmental toxins)

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3
Q

what is pharmacokinetic

A

study of how drugs are acted upon by physiological functions
essentially what the body does with the drug

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4
Q

describe the overview movement of drugs

A

a drug enters the body, circulates thorugh body, changed by the body, leaves the body

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5
Q

what are the 4 major steps of drug movement in the body and time course

A

AD & ME

Absorption - input
Distribution - drug in tissues; highway (plasma, blood supply, etc.)
Metabolism (biotransformation) - metabolizes to be eliminated from the body
Excretion (elimination) - output; drug is eliminated through urine, bile, feces, breath etc.

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6
Q

describe drug absorption

A

can occur by a number of mechanisms designed to either exploit or breach the body’s physiologic barriers
Method of drug administration greatly affects its absorption

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7
Q

Method of drug administration does not affect its absorption

A

false
it does

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8
Q

describe drug distribution

A

Following absorption, the drug will utilize the body’s distribution systems such as blood and lymphatic vessels to reach its target in an appropriate concentration

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9
Q

The ability of the drug to access its target site also is limited by several patient processes
These processes fall broadly into two categories

A

drug metabolism
drug excretion

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10
Q

describe drug metabolism

A

The body inactivates the drug through enzyme degradation especially in the liver

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11
Q

describe drug excretion

A

After being metabolized, the drug is excreted out of the body
Primarily through the kidneys (urine), liver (bile), and gut (feces)

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12
Q

enteral route

A

Drugs given by this route are placed directly into the gastrointestinal tract and includes
oral administration
rectal administration

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13
Q

topical route

A

Drugs applied to the surface of body and includes
transdermal administration (skin patches or ointments)
otic - ear drops
nasal - nose drops
opthalmic - eye drops

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14
Q

topical

A

applied on the surface
ex: ct scan with contrast etc.
only stays on the skin and the skin layers

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15
Q

transdermal

A

applied on the skin as well (patches)
but penetrates through the skin layer to effect on more distant parts

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16
Q

routes of drug administration

A

oral
sublingual - tongue
buccal -cheek or into jaw
transdermal - topical
injection
intranasal
ophthalmic
otic

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17
Q

benefit and limitation of enteral route

A

simplest of all routes

Ease of self administration; no skilled medical care needed
Very portable
Less likely to introduce systemic infections unlike parenteral route

route does expose the drug to harsh environments
Lipid soluble drugs pass through the GI tract most easily
Food in the stomach may or may not alter the rate of absorption
pH of the stomach and drug may interfere with drug absorption
Presence of other drugs in the stomach may cause a drug interaction (in the oral route)
Drugs go through a first-pass metabolism in the liver

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18
Q

describe the purpose of drug development

A

whole purpose of designing a drug is going to the correct receptor with the correct dosage and some are better favored to go one route than another

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19
Q

injection vs pill form of a drug

A

injection - effect very quickly in s
pill- takes longer 30-40 min

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20
Q

what is first pass metabolism in the liver

A

process by which a drug’s concentration is significantly reduced before it reaches the systemic circulation. This process occurs mainly in the liver and sometimes in the intestines after the drug is absorbed from the gastrointestinal tract.

Drugs that are administered orally pass from the GI tract to the portal veins and enter the liver before entering the systemic circulation
This system protects individuals from the effect of ingested toxins, which are detoxified in the liver

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21
Q

checkpoint

A

liver
checking for any toxins
can parts of the drug cause damage to the body

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22
Q

Any drug that exhibits first-pass metabolism must have appropriate dosage to ensure effective concentration on target organs because of some inactivation in the liver

A

true

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23
Q

Non-enteral routes of administration are subject to the first-pass metabolism by the liver

A

FALSE

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24
Q

pill form dosage will always be higher than injection form

A

true

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25
90% of oral medication is metabolized and destroyed by the liver before it gets to the heart
true
26
steps of first pass metabolism
oral med sits in stomach for 30-45 min portal circulation: blood from intestines goes to liver for detoxification liver: metabolizes 90% of oral meds
27
benefits of parenteral administration
intravenous (IV) administered drug is immediately available in the circulation intramuscular (IM) or subcutaneous (SC) administration has a slower entry into the circulation than I/V but faster than enteral administration fast onset of drug action bioavailability of drug is 100% IV - more controlled delivery; continuous meds one injection can last days to months
28
The amount of drug reaching the system will be the same for all routes of parental administration
true
29
non-intravenous parental routes will take longer for the drug to reach peak values in the circulation
true
30
IV onset
15 - 30 s
31
IM & SC onset
3-5 mins
32
routes used for oil-based drus
IM & SC
33
drugs too irritant for the drug and administered parenteral
chemotherapeutic drugs
34
disadvantages to parenteral administration
Greater risk of addiction with drugs that are injected as the onset of action is very rapid Not practical for patients who cannot self administer injections Belonephobia (fear of needles and injections) limits this route High risk for hepatitis, HIV, etc., if needles are shared Most dangerous route of administration as it bypasses all the body’s natural defenses, including the BBB if given intrathecally, exposing patients to death from adverse reactions or health problems Potentially fatal air bubbles (especially IV) can be introduced Strict asepsis is required Requires trained/skilled personnel; cost is generally much higher
35
Most dangerous route of administration as it bypasses all the body’s natural defenses, including the BBB if given intrathecally, exposing patients to death from adverse reactions or health problems such as
HIV, hepatitis, abscess, infections, drug additibes/contaminants
36
why is parenteral administration the most dangerous rourte?
because it bypasses the BBB and bypassing the body's defenses
37
what is bioavailability
subcategory of drug absorption how much of drug you took and how much of it is available amount of drug available in the circulation
38
how is bioavailability quantitatibely defined
bioavailability = Quantity of drug reaching systemic circulation ÷ Quantity of drug administered
39
I/V drugs are injected directly into
systemic circulation
40
drugs administered orally have a bioavailability of
< 1 primarily
41
drugs administered by IV have bioavailability of
generally 1 (maximum)
42
what is bioavailability dependent on
route of administration chemical form of the drug patient factors like gastrointestinal enzymes & pH and hepatic metabolism
43
Concept of bioavailability becomes important with generic drugs
have the same molecule structure, but concentration and route of administration may differ
44
Drugs soluble in aqueous solutions at physiologic pH often can be administered
orally
45
FDA mandates generics must have _______ of the bioavailabilityy of the parent compound
90%
46
After a drug is absorbed from its site of administration, it is distributed to its site of action primarily by the circulatory system (the blood plasma) and to a minor degree by the lymphatic system
true
47
why is the concentration of drugs in plasma is often used to determine therapeutic drug levels
because amount of drug actually taken up by target organs is difficult to measure
48
plasma concentration of a drug correlates well with the effect of the drug on its target site
true
49
what affects drug concentration in the plasma
Distribution of the drug in various tissues and compartments as well as blood flow variability between different organs affects drug concentration in the plasma liver and kidneys usually receive the most blood flow
50
what usually receives the most blood flow
liver and kidneys
51
Drugs occur in two forms in the blood
Bound to plasma proteins, most commonly albumin “Free” or unbound drug This is the active part of the drug
52
what is the active part of the drug
“Free” or unbound drug
53
car example for drug distribution
you sittin in the car, car going on the highway you are the drug, car is the protein, highway is the blood once the car and you go to the destination you decouple from the car (cannot bring car into the classroom) one that leaves the car (protein) unbound = bring about the change one that stays in the car (protein) bound = no action brought about
54
free vs bound drug
one that leaves the car (protein) unbound = bring about the change one that stays in the car (protein) bound = no action brought about
55
most abundant protein in the body
albumin
56
Ratio of bound:unbound drug remains the same in the blood
true
57
unbound drug from protein
brings about the change Exerts desired effect on target drug receptor sites in the target organ(s)
58
bound drug to proteins
no action is brought Remains in the compartment (vasculature) longer A drug that exhibits high level of protein binding requires a higher concentration
59
The processes by which biochemical (enzymatic) reactions alter within the body are collectively called
drug metabolism or drug biotransformation
60
waht happens in drug metabolism
reactions convert lipid soluble drugs to water soluble metabolites so that the drugs can be more easily excreted by the kidneys
61
contains the greatest quantity and diversity of metabolic enzymes
liver
62
drug metabolism aso happens in
kidneys, lungs, nerves, skin, plasma & GI Tract
63
where does most of drug metabolism happen
liver
64
Biotransformation reactions are classified as
Oxidation/Reduction or Phase I Conjugation/Hydrolysis or Phase II reactions
65
difference between phase I and first pass metabolism
first phase of metabolism in the liver after drug has exerted its effect and gone to receptor organs and now it is taken out of the body here and happens for all types of route of administer what is first pass metabolism? happens in the liver but happens with oral meds and it detoxifies it and happens before it goes into the blood stream before the drug goes to the receptor organs and only happens for the oral route location is the same but function and ____ are different they both happen in the liver
66
describe oxidation reduction (phase I)
exchange of ions Phase 1 reactions modify the chemical structure of a drug through oxidation/reduction The liver has enzymes that facilitate these reactions most common pathway in the liver is the cytochrome P450 system (CYP pronounced “sip” enzymes) that mediates oxidative reactions Some drugs are administered in an inactive prodrug form so that they can be metabolically altered in the liver to the activated form This prodrug strategy helps to
67
most common pathway in the liver
cytochrome P450 system (CYP pronounced “sip” enzymes) that mediates oxidative reactions
68
drugs are administered in an inactive ______ form so that they can be metabolically altered in the liver to the activated form
prodrug
69
prodrug strategy helps to
facilitate oral bioavailability decrease GI toxicity prolong elimination of ½ life of a drug
70
what is 1/2 life of a drug
time it takes for the concentration of the drug in the bloodstream or body to reduce by half.
71
if a drug has a half-life of 4 hours, and you take a dose of 100 mg, after 4 hours, _____ mg of the drug will remain in your body. After another 4 hours, _____ mg will remain, and so on
50 25
72
primary machine for metabolizing drug
cyp enzymes
73
involved in metabolism of about 75% of all drugs used today
cytochrome P450 (CYP) enzymes
74
more CYP = faster drug metabolism less CYP = slower drug metabolism
true
75
If cytochrome P450 liver enzymes (CYP enzymes) are induced,
if you increase enzyme you increase metoblism (more breakdown) and drug leaves the body faster
76
If cytochrome P450 liver enzymes are inhibited, it
if there is less of the enzye there is less breakdown so it stays longer in the body
77
If cytochrome P450 liver enzymes (CYP enzymes) are induced, it would increase the rate of metabolism increasing the rate of metabolism would ______ the action of the drug
decrease
78
If cytochrome P450 liver enzymes are inhibited, it would decrease the rate of metabolism (drugs stays in the body longer) decreasing the rate of metabolism would _______ the action of the drug
increase
79
inhibition of cyp enzymes results in
less eyymes, less breakdown and drug stays in the body longer
80
induced CYP enzynes results in
increased enzymes which increases the breakdown which causes the drug to leave the body faster
81
what is conjugatioin
forming a compound by joining two or more chemical compounds
82
what is hydrolysis
reaction involving breaking of a bond in a molecule using water
83
describe phase II conjugation/hydroysis
hase II reactions hydrolyze or conjugate a drug to a larger polar molecule by adding other molecular groups such as glutathione, sulfate, and acetate This reaction inactivates the drug or enhances the drug solubility and excretion rate into urine or bile
84
effect of Phase I and II reactions on a particular drug also are dependent on presence of other drugs taken by the patient at the same time
true
85
what are barbiturates
sedatives inducers of enzymes mediating phase I reactions
86
taking barbituates are inducers so they will leave the body faster
true
87
other drugs that inhibit cause the drug to stay in the body longer
true
88
what drugs inhibit enzynes?
erythromycin
89
polypharmacology
taking several drugs together
90
3 outcomes of phase I and II of the liver reactions
Convert an active drug to inactive most common outcome inactive drug formed from the active parent drug Convert an inactive drug form (prodrug) to active inactive parent drug is converted to active drug after metabolism Convert an active drug to active an active parent drug is convrted to a second active drug
91
function of Phase I and II biotransformation is to
enhance the hydrophilic nature of a hydrophobic drug so that it can be excreted easily out of the body
92
what is excretion
movement of a drug and/or its metabolites out of the body
93
how is a drug excreted
Primarily through renal excretion (urine) Also through biliary excretion (feces) Minor amounts through respiratory (breath – i.e., alcohol, useful for Breathalyzer), and dermal routes (sweat) Even smaller amounts through breast milk during lactation
94
25% of the entire blood in the body goes to the kidneys
true
95
why are kidneys are continually exposed to drugs in the blood stream
Renal flow comprises ~25% of total systemic blood flow
96
If a drug is still fat soluble when it reaches the kidney, it will be reabsorbed by the kidneys and placed back into the bloodstream
true
97
kidney function will affect drug excretion because
majority of drugs in the blood stream are filtered and excreted out by the kidneys
98
kidney function is affected, then excretion of the drug will take longer and can increase drug toxicity
true increases toxicity and overdose
99
Kidney function is affected by many conditions including
Age (kidney function declines with age) Drug toxicity Altered kidney function from disease such as diabetes (impaired renal blood supply) hypertension renal diseases - polycystic kidneys & glomerulonephritis from any case cancers (diabetes, high blood pressure, tumors, cancer, polycystic, genetic conditions (alport, BOR) )
100
what is drug clearance
rate of elimination of a drug from the body relative to the concentration of the drug in the plasma rate at which the drug would need too be cleared from the plasma to account for the change sought by the drug in the body
101

Pharm & Ototoxicity (10 decks)

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