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Chemo & Drug Assessment > Drug Interactions > Flashcards

Drug Interactions Flashcards

1
Q

drug interactions in vitro commonly occur from

A

formulation or combination of drugs in IV bags in hospital settings

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2
Q

facotrs which impact absorption in the intestines (2)

A
  • pH changes
    • alter ration of ionized: non-ionized forms of a drug
  • motility
    • delayed gastric emptying and reduced gut motility delay absorption
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3
Q

non-ionized drugs are more lipid soluble and therefore more readily absorbed True or false

A

true

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4
Q

Factors affecting drug interactions in the intestines include

A
  • ionic interactions
  • drug drug absorption interactions
  • effect of diet
  • kitamin k
  • enterohepatic shunt
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5
Q

ionic interactions in the intestine impact drug interactions and reduce effectiveness by

A
  • forming inactive complexes with divalent or triavlent ions
    • e.g. tetracycline and milk or antacids (Ca2+, Mg3+)
  • interfering with absorption of aspirin, warfarin by acidic molecules
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6
Q

warfarin is inhibited by

A

pentobarbitone

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7
Q

high fat diets are an example of how diet can enhance solubility of lipid soluble drugs and cause

A
  • can cause drug ineffectiveness if drug is not intended to be absorbed in GIT
  • may cause systemic absorption causing more toxicity
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8
Q

grapefruit juice is another example of the effect of diet on drug interactions and causes

A

agumented oral bioavailability of CYP3A4 drugs

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9
Q

coumarin and indanedione anticoagulants are Vitamin K

A

antagonists

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10
Q

interactions of drugs with vitamin K antagonists cna lead to what

A

bleeding episodes

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11
Q

these drugs reduce the absorption of vitamin k

A
  • chloramphenicol
  • chlortetracycline
  • neomycin
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12
Q

use of antibiotics with people on coumadin are challegning as they

A

reduce the microbial synthesis of vitamin K which causes plasma levels to drop potentiating the anticoagulant activity of warfarin

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13
Q

the enterohepatic shunt allows for

A
  • the recirculation of drug secreted into the bile back into the intestine where it re-enters circulation
  • this causes increased persistence of drug and increased duration of action
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14
Q

these drugs inhibit the enterohepatic shunt and may cause failure of contraceptives

A

antimicrobials

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15
Q

what is the hERG channel

A
  • human ether-agogo related gene
  • cardiac potassium channel
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16
Q

what is the major difference b/t hERG and normal potassium channels

A
  • gating kinetics
  • hERG channel target for Class III antidysrhthmic drugs
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17
Q

individuals with genetic abnormalities in hERG channels predispose them to

A

Long QT syndrome

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18
Q

Long QT syndrome is

A
  • long QT interval
  • ventricular dysrythmia
    • torsades de Pointes (sudden ddeath)
19
Q

what is acquired long QT syndrome caused by

A
  • electrolyte imbalances (potassium and magnesium)
  • hERG channel drug use
20
Q

what are some examples of drugs which target hERG as their mechanism of action

A
  • antidysrhythmic drugs
    • amiodarone
    • quinidine
    • procainamide
  • chlorpormazine
  • haloperidol
  • erythromycin
  • clarithromycin
21
Q

enzyme induction related drug interactions occur when

A

one drug has the ability to induce enzymes responsible for the metabolism of other drugs

22
Q

chronic administration of a drug can cause tolerance by

A

inducing enzymes responsible for the metabolism of the drug

23
Q

what are two drugs that are examples of enzyme induction and drug interaction, and what happens

A
  • barbituates and anticoagulants
  • enzyme induction by the administration of barbituates causes the metabolism of vitamin K anticoagulants reducing their effectiveness
24
Q

True/False: drug interactions can occur when two structurally similar drugs compete for the same enzyme

what is an example

A
  • True
  • trycylic antidepressants and phenothiazine tranquilizers
    • e.g. amytriptyline and phenotiazine
25
Q

in the case of amitryptiline and phenothiazine tranquilizers, what happens when enzyme inhibition via competion occurs

A
  • the activity of the tricyclic can be inhibited
  • the drug is not metabolized
  • antidepressants inhibitors of catecholamines which increase sympathetic effects
    • increased hypertension, cardiac events
26
Q

Monoamine oxidase inhibitors (MAOIs) can

A
  • reduce sympathetic drive
  • enhace parasympathetic drive
  • interact with many foods
27
Q

after treatment with an MAOI there is a build up of noradrenaline in the nerve terminal and a greater release of noradrenaline which causes

A

hypertensive crisis, hemorrhage and cerebral bleeding/stroke

28
Q

these drugs are contraindicated with MAOIs as their affect can be enhanced

A
  • amphetamine
  • ephedrine, pseudoephedrine (cough syrups)
29
Q

many drug interactions occur because of mixed function oxidase system

A

cytochrome P450

30
Q

CP450 metabolism mainly occurs in the

A

liver

31
Q

CP450 enzymes also exist in

A

intestines, lungs, orther organs

32
Q

poor metabolizers of drugs are at risk because

A
  • drug may accumulate to toxic levels due to inability to metabolize
  • cannot change a prodrug into its active form
  • or have less response
33
Q

what are some of the different types of cytochome P450 isoforms

A
  • CYP2D6
  • CYP1A2
  • CYP2E1
  • CYP3A
  • CYP3A4
34
Q

drugs which are bound to albumin are active or inert

A

inert

35
Q

True/False: drug interactions can commonly occur due to displacement of drugs bound to plasma proteins increasing the soluble concentraton

A

True

36
Q

how is the effect of drug displacement from binding sites calculated

A

=1+ (% bound + % Displaced)/ (1500 x % unbound)

37
Q

drug interaction at binding sites can occur as a result of

A
  • competitive antatognism
  • physiological antagonism
  • physiological addition/augmentation
  • drug synergism
  • drug interaction at nerve terminal
38
Q

drug interaction by competitive antagonism occurs when

A
  • an agonist and antagonist are competing for the same receptor site
39
Q

why is drug interaction by competitive antagonism unlikely to occur

A
  • the clinician would be prescribing drugs to do opposite things
40
Q

physiological antagonism is when

A

the action of one drug at a recoptor site opposes the actions of a drug at a different receptor site

41
Q

thiazide diuretics promote loss of K+ and convert a normal dose of cardiac glycosides to a fatal toxic dose. this is an example of what type of drug interaction

A

physiological augmentation

42
Q

effect produced by a combination of two or more drugs is greater than the effect of each on its own

A

drug synergism

e.g. alcohol and antihistamines

43
Q
A

Chemo & Drug Assessment (10 decks)

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