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Flashcards in Drug Interactions Deck (33)
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1
Q

Define pharmacodynamics

A

effect or change that a drug has on the body

2
Q

Does an agonist produce a PK or PD effect

A

PD-it binds to and activates a receptor producing some type of response

3
Q

Does an antagonist block a PK or PD effect

A

PD-it binds to the same receptor as an agonist but does not produce a reaction

4
Q

Define synergism

A

synergism is present when the effect from 2 drugs taken in combo is greater than the effect from simply adding the 2 individual effects together

5
Q

Define pharmacokinetic

A

The effect or change that the body has on the drug

6
Q

ADME is PK or PD?

A

PK

7
Q

ADME stands for?

A

Absorption, distribution, metabolism, excretion

8
Q

Chelation a PK or PD?

A

PK-drug binds to charged ions in another compound

9
Q

Inducers/Inhibitors a PK or PD?

A

PK-most PK interactions occur during metabolism

10
Q

Define metabolism

A

breakdown of drugs in the body into forms that can be removed

11
Q

For a drug to be renally excreted do they need to be water-soluble (polar, charged) or lipid-soluble (non-polar, uncharged)

A

water-soluble: urine is mostly water

12
Q

Phase-1 metabolism

A

chemical reactions that change the parent molecule into a metabolite. Most are oxidation reactions, but can be hydrolysis or reduction reactions. Phase 1 reactions usually inactivate the compound

13
Q

Phase-2 metabolism

A

mainly conjugation reactions. conjugation means “joined together”. An enzyme binds the compound to another substance (glucuronide, glutathione, or sulfate) to increase water solubility and facilitate elimination.

14
Q

First-pass metabolism

A

the changes made to a drug in phase 1/2 reactions prior to the drug reaching the systemic (blood) circulation

15
Q

Are cyp enzymes phase 1 or phase 2 metabolism

A

phase 1

16
Q

What does an enzyme inducer do?

A

cause more enzyme production or increase enzyme activity, which increases the rate of drug metabolism. Substrates for the enzyme will then have a decrease in serum drug level. in some cases more drug will be lost to first pass metabolism.

17
Q

Major CYP inducers (anagram)

A
PS PORCS
phenytoin
smoking
phenobarbital
oxcarbazepine
rifampin
Carbamazepine
St. John's Wort
18
Q

inducers/inhibitors effects on prodrugs

A

inhibitor=decrease active drug

inducer=increase active drug

19
Q

Major Cyp inhibitors (anagram)

A
G <3 PACMAN
Grapefruit
Heart
PIs-protease inhibitors (ritonavir)
Azole antifungals
C: cyclosporine, cimetidine, cobicistat
Macrolides- not azithromycin
Amiodarone
Non-DHP CCBs: diltiazem, verapamil
20
Q

time frame to see inducers and inhibitors work

A

inhibition is fast-in a few days and will end quickly when it is d/c
induction often requires additional enzyme production which takes time. the full effect may not be seen for up to 4 weeks. when it is stopped it could take 2-4 weeks for the induction to disappear completely

21
Q

P-gp efflux pumps purpose

A

located in many tissues where they provide protection against foreign substances by moving them out of critical areas

22
Q

P-gp transporters effects on drugs

A

transports drugs and their metabolites out of the body by pumping them into the gut, where they can be excreted in the stool

23
Q

P-gp substrates

A

Anticoagulants
CV drugs-coreg, digoxin, ranolazine
Immunosuppressants-CsA, tacro, sirolimus
HCV drugs-dasabuvir, ombitasvir, paritaprevir, sofosbuvir
Others-atazanavir, colchicine, dolutegravir, posaconazole, raltegravir, saxagliptin

24
Q

P-gp inducers

A
carbamazepine
dexamethasone
phenobarbital
phenytoin
rifampin
St. John's Wort
tipranavir
25
Q

P-gp inhibitors

A

Anti-infectives: clarithromycin, itraconazole, posaconazole
CV drugs: amio, coreg, conivaptan, dronedarone, diltiazem, quinidine, verapamil
HIV: cobicistat, ritonavir
HCV: daclatasvir, ledipasvir, paritaprevir
Others: CsA, flibanserine, ticagrelor

26
Q

Enterohepatic recycling

A

After a drug has been metabolized, it can be transported through the bile back to the gut. from the gut the drug can be reabsorbed again usually in the small intestine. it increases the duration of action of many drugs

27
Q

2 common drugs that undergo enterohepatic recycling

A

NSAIDs, ezetimibe

28
Q

Amiodarone + Warfarin

A

Amio inhibits Cyp2C9 to decrease warfarin metabotims and increase INR

  • if on amio start warfarin at 5mg
  • if on warfarin then add amio decrease warfarin by 30-50%
29
Q

Amiodarone + Digoxin

A

Amiodarone inhibits P-gp and digoxin is a substrate
decrease digoxin excretion inc. ADR/toxicity
inc risk of bradycardia

30
Q

Warfarin + EN

A

EN binds warfarin = low INR

hold tube feeds 1 hour before and after warfarin

31
Q

Tetracycline, quinolones, levothyroxine + EN

A

will chelate with metals, including Ca, Mg, and Fe which reduces drug availability, separate from tube feeds

32
Q

Cipro + EN

A

oral suspension is not sued with tube feeds because the oil-based suspesion adheres to the tube. the immediate-release tablets are used instead; crush and mix with water, flush line with water before and after

33
Q

Phenytoin + EN

A

levels are reduced when the drug binds to the feeding solution, leading to less free drug availablility and sub-therapeutic levels. separate tube feeds by 2 hours