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Pharm & Ototoxicity > Principles of Pharmacokinetics > Flashcards

Principles of Pharmacokinetics Flashcards

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
Q

90% of oral medication is metabolized and destroyed by the liver before it gets to the heart

A

true

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26
Q

steps of first pass metabolism

A

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

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27
Q

benefits of parenteral administration

A

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

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28
Q

The amount of drug reaching the system will be the same for all routes of parental administration

A

true

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29
Q

non-intravenous parental routes will take longer for the drug to reach peak values in the circulation

A

true

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30
Q

IV onset

A

15 - 30 s

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31
Q

IM & SC onset

A

3-5 mins

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32
Q

routes used for oil-based drus

A

IM & SC

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33
Q

drugs too irritant for the drug and administered parenteral

A

chemotherapeutic drugs

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34
Q

disadvantages to parenteral administration

A

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

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35
Q

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

A

HIV, hepatitis, abscess, infections, drug additibes/contaminants

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36
Q

why is parenteral administration the most dangerous rourte?

A

because it bypasses the BBB and bypassing the body’s defenses

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37
Q

what is bioavailability

A

subcategory of drug absorption

how much of drug you took and how much of it is available

amount of drug available in the circulation

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38
Q

how is bioavailability quantitatibely defined

A

bioavailability = Quantity of drug reaching systemic circulation ÷ Quantity of drug administered

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39
Q

I/V drugs are injected directly into

A

systemic circulation

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40
Q

drugs administered orally have a bioavailability of

A

< 1 primarily

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41
Q

drugs administered by IV have bioavailability of

A

generally 1 (maximum)

42
Q

what is bioavailability dependent on

A

route of administration
chemical form of the drug
patient factors like gastrointestinal enzymes & pH and hepatic metabolism

43
Q

Concept of bioavailability becomes important with generic drugs

A

have the same molecule structure, but concentration and route of administration may differ

44
Q

Drugs soluble in aqueous solutions at physiologic pH often can be administered

A

orally

45
Q

FDA mandates generics must have _______ of the bioavailabilityy of the parent compound

A

90%

46
Q

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

A

true

47
Q

why is the concentration of drugs in plasma is often used to determine therapeutic drug levels

A

because amount of drug actually taken up by target organs is difficult to measure

48
Q

plasma concentration of a drug correlates well with the effect of the drug on its target site

A

true

49
Q

what affects drug concentration in the plasma

A

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
Q

what usually receives the most blood flow

A

liver and kidneys

51
Q

Drugs occur in two forms in the blood

A

Bound to plasma proteins, most commonly albumin
“Free” or unbound drug
This is the active part of the drug

52
Q

what is the active part of the drug

A

“Free” or unbound drug

53
Q

car example for drug distribution

A

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
Q

free vs bound drug

A

one that leaves the car (protein) unbound = bring about the change

one that stays in the car (protein) bound = no action brought about

55
Q

most abundant protein in the body

A

albumin

56
Q

Ratio of bound:unbound drug remains the same in the blood

A

true

57
Q

unbound drug from protein

A

brings about the change
Exerts desired effect on target drug receptor sites in the target organ(s)

58
Q

bound drug to proteins

A

no action is brought

Remains in the compartment (vasculature) longer

A drug that exhibits high level of protein binding requires a higher concentration

59
Q

The processes by which biochemical (enzymatic) reactions alter within the body are collectively called

A

drug metabolism or drug biotransformation

60
Q

waht happens in drug metabolism

A

reactions convert lipid soluble drugs to water soluble metabolites so that the drugs can be more easily excreted by the kidneys

61
Q

contains the greatest quantity and diversity of metabolic enzymes

A

liver

62
Q

drug metabolism aso happens in

A

kidneys, lungs, nerves, skin, plasma & GI Tract

63
Q

where does most of drug metabolism happen

A

liver

64
Q

Biotransformation reactions are classified as

A

Oxidation/Reduction or Phase I

Conjugation/Hydrolysis or Phase II reactions

65
Q

difference between phase I and first pass metabolism

A

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
Q

describe oxidation reduction (phase I)

A

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
Q

most common pathway in the liver

A

cytochrome P450 system (CYP pronounced “sip” enzymes) that mediates oxidative reactions

68
Q

drugs are administered in an inactive ______ form so that they can be metabolically altered in the liver to the activated form

A

prodrug

69
Q

prodrug strategy helps to

A

facilitate oral bioavailability
decrease GI toxicity
prolong elimination of ½ life of a drug

70
Q

what is 1/2 life of a drug

A

time it takes for the concentration of the drug in the bloodstream or body to reduce by half.

71
Q

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

A

50
25

72
Q

primary machine for metabolizing drug

A

cyp enzymes

73
Q

involved in metabolism of about 75% of all drugs used today

A

cytochrome P450 (CYP) enzymes

74
Q

more CYP = faster drug metabolism
less CYP = slower drug metabolism

A

true

75
Q

If cytochrome P450 liver enzymes (CYP enzymes) are induced,

A

if you increase enzyme you increase metoblism (more breakdown) and drug leaves the body faster

76
Q

If cytochrome P450 liver enzymes are inhibited, it

A

if there is less of the enzye there is less breakdown so it stays longer in the body

77
Q

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

A

decrease

78
Q

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

A

increase

79
Q

inhibition of cyp enzymes results in

A

less eyymes, less breakdown and drug stays in the body longer

80
Q

induced CYP enzynes results in

A

increased enzymes which increases the breakdown which causes the drug to leave the body faster

81
Q

what is conjugatioin

A

forming a compound by joining two or more chemical compounds

82
Q

what is hydrolysis

A

reaction involving breaking of a bond in a molecule using water

83
Q

describe phase II conjugation/hydroysis

A

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
Q

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

A

true

85
Q

what are barbiturates

A

sedatives
inducers of enzymes mediating phase I reactions

86
Q

taking barbituates are inducers so they will leave the body faster

A

true

87
Q

other drugs that inhibit cause the drug to stay in the body longer

A

true

88
Q

what drugs inhibit enzynes?

A

erythromycin

89
Q

polypharmacology

A

taking several drugs together

90
Q

3 outcomes of phase I and II of the liver reactions

A

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
Q

function of Phase I and II biotransformation is to

A

enhance the hydrophilic nature of a hydrophobic drug so that it can be excreted easily out of the body

92
Q

what is excretion

A

movement of a drug and/or its metabolites out of the body

93
Q

how is a drug excreted

A

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
Q

25% of the entire blood in the body goes to the kidneys

A

true

95
Q

why are kidneys are continually exposed to drugs in the blood stream

A

Renal flow comprises ~25% of total systemic blood flow

96
Q

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

A

true

97
Q

kidney function will affect drug excretion because

A

majority of drugs in the blood stream are filtered and excreted out by the kidneys

98
Q

kidney function is affected, then excretion of the drug will take longer and can increase drug toxicity

A

true
increases toxicity and overdose

99
Q

Kidney function is affected by many conditions including

A

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
Q

what is drug clearance

A

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
Q
A

Pharm & Ototoxicity (10 decks)

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