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Pharmacology I > Test 1 Part IV > Flashcards

Test 1 Part IV Flashcards

1
Q

saying the clearance of a drug is 2mg/min would be an example of __________________

A

zero order kinetics

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2
Q

define half life

A

the time it takes for the total amount of drug in the body to be reduced by 1/2

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3
Q

_________ half lives must elapse before the full effect of a dosing regiment can be seen

A

4

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4
Q

a drugs half life is dependent on what two factors

A

Vd and clearance

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5
Q

define bioavailability

A

the fraction of unchanged drug reaching systemic circulation following administration

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6
Q

what is the bioavailability of any drug administered IV assumed to be?

A

100%

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7
Q

what decreases the bioavailability of drugs administered PO?

A

poor absorption across the GI tract
first pass elimination

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8
Q

what are the two main organs that affect the bioavailability of drugs administered PO

A

liver and GI tract

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9
Q

when is a loading dose utilized

A

when drugs have long half lives

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10
Q

what is the goal with the loading dose?

A

to promptly raise blood concentration levels

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11
Q

what is the most important influencing factor with dosing a loading dose?

A

volume of distribution (Vd)

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12
Q

what is the most important influencing factor with dosing a maintenance dose

A

clearance

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13
Q

what is the purpose of the mainteance dose?

A

to keep a steady state of drug in the body. just enough is given to replace what was eliminated since the preceding dose

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14
Q

T/F: rate of administration may be crucial with a loading dose

A

true

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15
Q

what can be an adverse effect of a loading dose

A

transient, potentially severe toxicity

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16
Q

what is biotransformation

A

a process of drug metabolism that alters the chemical structure of a lipid soluble drug to make it water soluble for elimination

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17
Q

only ______________ substances can be excreted in the kidneys

A

water soluble

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18
Q

byproduct metabolites formed from biotransformation are often _____________ pharmacologically active than the parent drug, but they could also be _____________, _____________, or _______________

A

less; inactive; more enhanced activity; toxic activity

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19
Q

what is the principle organ of drug metabolism and thus also of biotransformation

A

liver

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20
Q

what are other areas of drug metabolism besides the liver

A

GI tract, Lungs, skin, kidneys, brain

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21
Q

the _________________ harbors a lot of micro-organisms that are capable of many biotransformation reactions

A

lower gut

22
Q

if there is compromise of the liver, primary site of metabolism for drug A, what can be the result?

A

significant elevations of plasma levels, which is clinically relevant in drug-drug interactions

23
Q

drug metabolizing enzymes are found specifically in the ________________ of the liver

A

endoplasmic reticulum

24
Q

what are the phases of biotransformation

A

phase I - oxidative reduction
phase II - conjugation

25
Q

in phase I of biotransformation, oxidation =

A

P450 + P450 reductase + NADPH + O2

26
Q

the oxidation process of phase I biotransformation will consume one molecule of ___________ (reduced) and produce ______________ + _____________

A

O2; a metabolite; H2O

27
Q

which phase of biotransformation changes the polarity of the drug

A

phase I - oxidation

28
Q

if a metabolite produced from a phase I reaction is sufficiently polar it will be ______________; if not then it will ________________

A

excreted; undergo phase II reaction

29
Q

what are the 2 key enzymes involved in the phase I (oxidative reduction) of biotransformation

A

NADPH-cytochrome P450 oxidoreductase (flavoprotein)
and Cytochrome P450

30
Q

what would increase the availability of P450s

A

repeated administration of or exposure to exogenous chemicals

31
Q

what does CYP (P450) “induced” mean

A

there is an enhanced rate of synthesis or reduced rate of degradation

32
Q

what are the results/consequences of being CYP (p450) “induced”

A
  1. results in accelerated metabolism and usually in a decrease in the pharmacologic action of the inducer and co-administered drugs
  2. may exacerbate metabolite mediated toxicity
33
Q

what environmental/occupational factors have been found to be capable of inducing P450 enzymes

A
  1. smoking
  2. industrial workers
  3. those that work with insecticides
34
Q

what drugs have been found to be P450 inducers

A
  1. antipsychotics
  2. various sedative-hypnotics
  3. anticonvulsants
  4. rifampin
35
Q

in general, if a drug is a p450 inducer or inhibitor it is safe to assume what?

A

all drugs within that class have same action on P450

36
Q

if something is a P450 inhibitor, what is the result

A

decreased metabolism

37
Q

what is the mechanism at which a drug is a P450 inhibitor?

A

tells the apo protein responsible for making the P450 not to make it –> decreases metabolism

38
Q

_____________ is responsible for metabolizing over 50% of prescription drugs metabolized in the liver

A

CYP3A4

39
Q

P450 is an enzyme, and is specifically a ________________

A

hemoprotein

40
Q

if an enzyme is described as microsomal, you know that means what?

A

they are a part of the Smooth ER and Rough ER

41
Q

what are the microsomal reactions of a phase I biotransformation reaction

A

Cytochrome P450 oxidation

42
Q

what are the non-microsomal reactions of a phase I biotransformation reaction

A

oxidation and hydrolysis

43
Q

phase II of biotransformation is called ___________________

A

conjugation

44
Q

define what happens in the Phase II (conjugation) biotransformation reaction

A

metabolic byproducts (not sufficiently polar) of phase I are further conjugated into highly polar molecules by an endogenous substrate

45
Q

phase II of biotransformation forms drug conjugates, what is the purpose of this?

A

makes the drug metabolites highly polar, which makes them readily excreted and often inactivated

46
Q

what endogenous substrates are commonly used in a phase II biotransformation reaction

A

glucuronic acid, sulfuronic acid, acetic acid, amino acid

47
Q

where do endogenous substrates for phase II biotransformation reaction come from

A

diet and often affected by nutrition status

48
Q

2 drugs may compete for the same endogenous substrate during a phase II biotransformation reaction, what could be the result of this

A

the faster drug may deplete substrate reserves and impair the metabolism of the slower reacting drug.
if the slower reacting drug has a narrow therapeutic index –> toxicity/death

49
Q

what is required for a phase II biotransformation reaction to occur

A
  1. endogenous substrate
  2. energy
  3. transferase
50
Q

what is the most dominant transferase enzyme found in the cytoplasm for phase II biotransformation reaction

A

uridine 5’-diphosphate-flucuronosyl transferases (UGTs)

Pharmacology I (16 decks)

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