Chapter 3: Drug Interactions Flashcards

1
Q

Definition of

Additive Effect

A

Two drugs with similar effects, regardless of mechanism, when given together can cause increased effectiveness or ADEs

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2
Q

Example of

Additive Effect: Same receptor

A

Two opioids (mu-receptor agonists) given together, pose increased risk of ADEs

Ex: sedation, respiratory depression, death

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3
Q

Example of

Additive Effects: differen receptors

A

Benzodiazepines (GABA) and opioids (mu), when given together pose an increased risk of fatal overdose.

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4
Q

Definition of

Antagonism interaction

A

when an antagonist blocks the agonist from binding to its receptor

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5
Q

Example of

Antagonism interaction

A

Naloxone (mu-ant) and opioids (mu-ag)
* naloxone reverses respiratory depression and analgesic effect of opioids

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6
Q

Definition of

Synergistic Effect

A

when two drugs taken in combination have a greater effect than the sum of its parts

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7
Q

Example of

Synergistic Effect

A

Oxycodone & Acetaminophen
* mechanism unknown

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8
Q

Definition of

Chelation

A

when a drug binds to polyvalent cations (Mg+, Ca++, Fe++) in another compound. The chelated compound cannot disolve in the gut fluid and will pass out in the stool

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9
Q

Example of

Chelation

A

Quinolone antibiotics bind to calcium containing drugs and dairy products -> will not be absorbed -> decreased efficacy

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10
Q

Examples of

drugs with polyvalent cations or other binding properties

A
  • antacids
  • multivitamins
  • sucralfate
  • bile acid resins
  • aluminum
  • calcium
  • iron
  • magnesium
  • zinc
  • phosphate binders
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11
Q

Examples of

Drugs that should be separated from chelation agents

A
  • quinolone antibiotics
  • tetracyclines
  • levothyroxine
  • oral bisphosphonates
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12
Q

The majority of PK drug interactions occur during:

A

metabolism in the liver (phase I or II reactions)

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13
Q

Ritonavir & Darunavir metabolic interaction

A

Ritonavir inhibits the metabolism of darunavir -> increased drug levels -> increased efficacy

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14
Q

Clarithromycin & Warfarin metabolic interaction

A

Clarithromycin inhibits warfarin metabolism -> increased warfarin levels -> increased bleed risk

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15
Q

Rifampin & Warfarin metabolic interaction

A

Rifampin induces warfarin metabolism -> decreased warfarin levels -> increased clotting risk

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16
Q

What is the primary route of drug excretion?

A

Renal excretion
* drug interactions can alter renal excretion

17
Q

Probenecid & Penicillin excretion interaction

A

Probenecid blocks renal excretion of penicillin -> increased penicillin levels -> allows penicillin to cross BBB to treat neurosyphilis

18
Q

Aspirin & Sodium Bicarbonate excretion interaction

A

Sodium bicarbonate alkalyses (inc pH) of urine -> increased clearance of aspirin -> treatment for aspirin overdose

19
Q

CYP450 enzymes are involved in which of the following:
* Phase I reactions
* Phase II reactions

A

Phase I reactions

20
Q

Prodrugs are used by manufacturers to:

A
  • extend the dosing interval (ex valacyclovir, prodrug of acyclovir)
  • prevent drug abuse (ex lisdexamphetamine Vyvanse prodrug of amphetamine)
21
Q

CYP enzyme inhibition occurs within:

A

A few days

22
Q

CYP enzyme induction occurs within:

A

2-4 weeks

23
Q

Common CYP inhibitors involved in DDIs

G PACMAN

A

Grapefruit
Protease inhibitors (esp ritonavi)r
Azole antifungals
Cyclosporine, cobicistat
Macrolides (clarithromycin & erythromycin, NOT azithromycin)
Amiodarone (& dronedarone)
Non-DHP CCBs
* diltiazem & verapamil

24
Q

Common CYP inducers involved in DDIs

PS PORCS

A

Phenytoin
Smoking

Phenobarbital
Oxcarbazepine
Rifampin (& rifabutin, rifapentine)
Carbamazepine
St. John’s wort

25
Q

Definition / Action of

P-gp efflux pumps

A

Permeability glycoprotien efflux pumps: transporters located in many tissue membranes, move foreign substances out of critical areas. P-gp pumps in the GI tract transport drugs and their metabolites out of the body by pumping them into the gut where they are excreted in the stool.

26
Q

Examples of

P-gp substrates

A
  • apixaban
  • rivaroxaban
  • digoxin
  • diltiazem
  • verapamil
  • cyclosporine
  • tacrolimus
  • colchicine
27
Q

Examples of

P-gp inducers

A
  • Carbamazepine
  • phenobarbital
  • phenytoin
  • rifampin
  • St. John’s wort
28
Q

Examples of

P-gp inhibitors

A
  • amiodarone
  • diltiazem
  • verapamil
  • cobicistat
  • ritonavir
  • cyclosporine
29
Q

Definition of

Enterohepatic recycling

A

Recycling of an already-metabolized drug
* metabolized in liver ->
* transported through bile to the gut ->
* reabsorbed in small intestine ->
* enter into portal vein ->
* travel back to liver