3 - drug interactions Flashcards

1
Q

what are two ways that drugs can interact

A

influence effectiveness by altering its availability (kinetics) or altering its interactions with its receptor (dynamic)

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2
Q

what is pharmacodynamics

A

What drug does to body

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3
Q

what is pharmacokinetics

A

what body does to drug

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4
Q

what is the pharmacokinetics consideration of drug interactions

A

how one drug may influence the effectiveness of another drug

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5
Q

what is the pharmacodynamic consideration of drug interactions

A

how one drug alters another drug’s interaction with its receptor

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6
Q

how does theraputic index relate to drug interactions

A

drugs with narrow theraputic index are most susceptible to issues with drug interactoins

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7
Q

what can result from a small change in availability of a drug

A

significant changes too outcome (too much causing toxic, too little so no therapy)

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8
Q

what is an antagonist interaction

A

drug A acts as an antagonist at receptor for drug B

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9
Q

is antagonist interaction a pharmacodynamic or pharmacokinetics

A

pharmacodynamic (drug does to body)

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10
Q

what is an example of an antagonist interaction?

A

vitamin K rich foods on warfarin

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11
Q

what is warfarin

A

anti-coagulant in patients with blood clot issues

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12
Q

how does warfarin work

A

inhibitor of Vit K epoxide reductase

this causes a reduction of clotting factors (red. VitK is used to make prothrombin)

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13
Q

what does VitK epoxide reductase do

A

recycle oxidized Vit K into reduced Vit K

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14
Q

what is a role of reduced vitamin K

A

helps make prothrombin

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15
Q

what is prothrombin time

A

measure of time required for blood to clot under a set of standard lab conditions

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16
Q

what is international normalized ratio

A

the ratio of the clotting time compared to a normal sample

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17
Q

what does a high what is international normalized ratio

A

sample requires a long time to clot

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18
Q

what does a low what is international normalized ratio

A

sample requires a short time to clot

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19
Q

what is the ideal international normalized ratio

A

2-3

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20
Q

what does vitamin K do to the effectiveness of warfarin

A

reduces it

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21
Q

how does vitamin K affect the effectiveness of warfarin

A

it is a competitive inhibitor for the enzyme (vit K epoxide reductase)

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22
Q

what happens to the effectiveness of warfarin if VItK is diminished

A

stronger effectiveness

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23
Q

what are synergism/additive interactions

A

multiple agonists/modulators that act on the same receptor leading to excessive activation

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24
Q

is additive/synergism interaction a pharmacodynamic or pharmacokinetics

A

pharmacodynamic (drug does to body)

25
Q

what does synergism mean

A

effects that are greater than the inividual effects of the two drugs

26
Q

what does additive mean

A

effects that are roughly the sum of the individual effects of two drugs

27
Q

what is an example of excessive receptor activation (synergism additive)

A

bezos, alcohol, barbiturates and other GABA A receptor modulators

28
Q

what is the mechanism of action of benzodiazepines

A

positive allosteric modulators of GABA A

29
Q

what is the mechanism of action of barbiturates

A

positive allosteric modulators or agonists of GABA A

30
Q

what is the mechanism of action of alcohol

A

positive allosteric modulators of GABA A

31
Q

what is the mechanism of action of zolpidem

A

positive allosteric modulators of GABA A

32
Q

is indirect interaction a pharmacodynamic or pharmacokinetics

A

pharmacodynamic

33
Q

what is indirect interaction

A

the effects of multiple drugs might influence the same signalling pathway, but not necessarily the same receptor

34
Q

what is an example of an indirect interaction

A

serotonin syndrome

35
Q

what is serotonin syndrome ( cause+effect)

A

arise from a combination of drugs that lead to an over abundanceof 5HT in the CNS and overstimulation of 5HT receptors (especially 5-HT2A and 1A)

36
Q

how do MAOIs contribute to serotonin syndrome

A

inhibit breakdown of 5HT

lots of them act irreversibly

37
Q

how do TCAs contribute to serotonin syndrome

A

prevent reuptake of 5HT from synaptic cleft

38
Q

how do SSRI contribute to serotonin syndrome

A

prevent reuptake of 5HT from synaptic cleft

39
Q

how do SNRI contribute to serotonin syndrome

A

prevent reuptake of 5HT from synaptic cleft

40
Q

how do some opioids contribute to serotonin syndrome

A

metabolites may have direct serotonergic effects or interfere with serotonin reuptake

41
Q

how do St. John’s wort contribute to serotonin syndrome

A

serotonin reuptake inhibitor

42
Q

how do MDMA and methamphetamine contribute to serotonin syndrome

A

use efflux pumps (transport in reverse)

43
Q

what are 2 ways of how can you alter drug availability pharmacokinetically

A

drugs that alter gut motility that affect absorption

drugs that alter local blood flow can alter absorption (lidocaine+epinephrine)

44
Q

how is lidocaine+epinephrine an example of pharmacokinetic drug interaction way to alter drug availability

A

alters absorption because the epinephrine vasoconstricts so that lidocaine can stay in the area

45
Q

what are two ways that CYP can be affected by food or drugs

A

induce expression of specific CYP enzymes (reduce lifetime and abundance of their substrates)
inhibit CYP activity (prolong lifetime and abundance of the substrates)

46
Q

what is the role of biotransformation

A

metabolism in the liver

47
Q

what is phase 1 biotransformation

A

oxidation via CYP

48
Q

what is phase 2 biotransformation

A

conjunction with large polar additions

49
Q

which enzymes metabolizes warfarin

A

CYP3A4

50
Q

which is the most common CYP enzyme

A

CYP3A4

51
Q

which food inhibits CYP3A4

A

grapefruit juice

52
Q

what happens to someone who has a lot of grapefruit who also takes warfarin

A

heightened sensitivity to warfarin or other drugs metabolized by CYP3A4

53
Q

what does grapefruit juice do to CYP3A4

A

inhibit it

54
Q

check online diagram he said hed post

A

make more questions

55
Q

what are product monographs

A

where the drug interactions are listed

56
Q

what is INR

A

the ratio of clotting time compared to a control

57
Q

what does high INR mean

A

the samples takes a long time to clot

58
Q

what does low INR mean?

A

sample doesn’t take long to clot

59
Q

how is prothrombin time measured

A

in INR (international normalized ratio)