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NAPLEX COPY > Drug Interactions > Flashcards

Drug Interactions Flashcards

1
Q

What enzyme metabolizes the majority of meds (75%)?

A

CYP 450 enzymes

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2
Q

Which specific CYP metabolizes 80% of the meds metabolized by CYP?

A

CYP 450 3A4 alone, or 3A4 and other enzymes

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3
Q

How do ALL enzymes in the body work?

A

By an enzyme-substrate system

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4
Q

What’s an enzyme?

A

Protein that performs some action

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5
Q

What’s a substrate?

A

A chemical that’s acted upon by an enzyme

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6
Q

What’s the main effect of an enzyme action?

A

Gen. inactivates drug metabolites (although, there are some times, the result in a toxic metabolite or beneficial metabolite)

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7
Q

Whats the first pass metabolism?

A

When the drug (substrate) passes through the gut wall and liver prior to reaching the systemic circulation

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8
Q

What are inducers?

A

Inducers are compounds (many of which are drugs) that either increase the PRODUCTION of the enzyme (by increasing the expression of the gene sequence that codes for the enzyme) or, increase the ACTIVITY of the enzyme

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9
Q

What’s the net effect of an inducer?

A

Increase the degree of drug metabolism, which results in LOWER blood levels of the substrate

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10
Q

Which med is one of the strongest inducers?

A

Rifampin

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11
Q

List the many enzymes that Rifampin induces

A

1A2

2C8, 2C9, 2C19

3A4

P-glycoprotein (P-gp) pump

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12
Q

Effect on warfarin dose, if pt is also started on Rifampin?

A

Warfarin dose will need to be increased 100-300% to maintain therapeutic INR

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13
Q

Effects of inducers on pro-drugs?

A

Inducer can increase the enzyme responsible for converting the substrate into a MORE active form (instead of less active or inactive form$

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14
Q

What’s the technical ref wrt prodrug conversion?

A

Bioactivation

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15
Q

What are inhibitors?

A

Compounds (many of which are drugs) that INHIBITS the activity of ENZYMES

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16
Q

Effect of inhibitor?

A

Enzyme inhibition results in LESS drug METABOLISM. T4 drug serum level (and therapeutic effect) will increase

Can result in drug toxicity

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17
Q

Effect of inhibitor on prodrug?

A

Inhibitor of the enzyme involved in bioactivation would block the production of the active form of the drug

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18
Q

Effects on Inducers on Substrate? On prodrugs?

A

Inducers DECREASE the conc of Substrate, EXCEPT with Prodrugs

T4 Inducers increase the conc of active metabolite of prodrug

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19
Q

Effects on Inhibitors on Substrate? On prodrugs?

A

Inhibitors INCREASE the conc of the substrate, EXCEPT prodrugs

T4 inhibitors decrease active metabolites of prodrugs

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20
Q

About 25% of drugs go through CYP 2D6, including many?

A

Pain and Psychiatric drugs

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21
Q

What are the practical considerations when d/c an inhibitor or inducer?

A

Consider the doses of other meds that have been increased or decreased bcuz of the use of the inducer or inhibitor.

So, before u d/c an inducer or inhibitor, check the status of the other meds they are using concurrently

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22
Q

Which has a “lag” time? Effect of the inhibition or Inducer?

A

Inducer: full effect may not be present for up to 2 wks. Similarly, it takes 2-4 wks for the induction to disappear completely

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23
Q

What’s P-glycoproteins (P-gp)?

A

Efflux transporters found in the gut and other organs.

They pump drugs back into the gut (to exit out of the body)

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24
Q

What happens if a drug is subject to efflux, and the transporter is inhibited by a different drug?

A

The substrate drug conc will INCREASE in the plasma

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25
Q

What happens to blood levels of a drug, if an inducer is given that causes the production of more pumps?

A

The blood levels of the substrate will DECREASE

26
Q

What’s P-gp inducer?

A

Causes the creation of more of the P-gp and blood levels go down

27
Q

Effect of P-gp on toxin?

A

If the toxin is a p-gp substrate, then it will reduce the amt of some toxin ingestion as well, by pumping them back into the gut

28
Q

What’s P-gp inhibitor?

A

Inhibits the drug-pump-inhibitor and consequently, blood levels of the drug increase

29
Q

List strong inhibitors of P-gp Efflux pump (results in increased in blood levels of the drug)

A

Itraconazole, Ketoconazole

Verapamil

Ritonavir; Lopinavir/Ritonavir; Indinavir/Ritonavir

Conivaptan

Clarithromycin; Eryhromycin

Amiodarone

Quinidine

30
Q

List strong inducers of P-gp Efflux pump (results in decreased in blood levels of the drug)

A

Rifampin

Avasimibe

Carbamazepine

Phenytoin

St. John’s wort

Tipranivir/Ritonavir

31
Q

List p-gp efflux pump substrates

A

Aliskiren

Colchicine

Dabigatran

Cyclosporine

Digoxin

Fexofenadine

Posaconazole

Ranolazine

Rivaroxaban

Saxagliptin

Tacrolimus

32
Q

Look at pg 192 for CYP 450 substrates, inducers and inhibitors

A

LOOK!

33
Q

List big inducers of CYP 450

A

PS PORCS (Big Inducers) - increase drug metabolism t4 lowering drug serum level

Phenytoin
Smoking

Phenobarbital 
Oxcarbazepine
Rifampin (and Rifabutin, Rifapentine)
Carbamazepine (and is an auto-inducer)
St. John's wort
34
Q

List big inhibitors of CYP 450

A

G PACMAN (Big Inhibitors) - reduce drug metabolism, t4 increasing serum drug level

Grapefruit

PIs - Protease Inhibitirs (esp Ritonavir)
Azoles antifungals - Fluconazole, Itraconazole, Ketoconazole,
Posaconazole, and Voriconazole
C - Cyclosporine and Cimetidine
Macrolides - Clarithromycin and Erythromycin, NOT Azithromycin, but
DO include the related compd, Telithromycin
Amiodarone (and Dronedarone)
Non-DHP CCBs (Diltazem and Verapamil)

35
Q

Are all Macrolides big CYP inhibitors?

A

No!

Azithromycin is NOT a big inhibitor of CYP

36
Q

Why’s cimetidine most difficult H2RA to use?

A

Big CYP inhibitor

Has androgen-blocking effects that can cause gynecomastia (swollen, or painful breast tissue or impotence)

37
Q

What meds must be reduced by 30-50% when starting Amiodarone?

A

Digoxin

Warfarin

Quinidine
Procainamide
Simvastatin, Lovastatin and Atorvastatin

38
Q

What drugs are most likely to be dosed with Amiodarone? Why?

A

Digoxin and Warfarin

Bcuz they are used in HF and arrhythmias

39
Q

T/F? If warfarin or digoxin is on board first, the pharmacist must recognize the interaction and decrease the dose when amiodarone is started?

A

True

40
Q

What’s medical conditions may cause an increase in digoxin levels?

A

Decline renal fxn

Hypokalemia

41
Q

What other considerations (other than amiodarone mentioned previously) may be considered when digoxin is used?

A

Additive drugs that lower HR (< 60 BPM)

Primarily beta-blockers and non-DHP CCBs (Diltazem and verapamil)

Others include:
Dexmedetomidine (Precedex), Clonidine and Opioids

42
Q

List drug interactions with grapefruit/ juice that are considered clinically significant

A

Rivaroxaban
- there could be an increased bleeding risk
Ticagrelor

QT prolongers + grapefruit/ juice = risk of torsades
Lurasidone
Quinidine

43
Q

Effect of Lamotrigine + Valproate used concurrently

A

Increased risk of rash

44
Q

List drugs not to use MAOI with

A

Ephedrine and analogs (Pseudoephedrine etc)

SSRIs, SNRIs, TCAs

Bupropion
Buspirone
Linezolid
Lithium
Meperidine
Tramadol
Levodopa
Mirtazapine
Dextromethropan 
Cyclobenzapine (and other skeletal muscle relaxants)
Some of the triptans
St. Johns wort
Procarbazine
Lorcaserin
45
Q

Hydrocodone and Tramadol interaction?

A

Those on 2D6 inhibitors:
Fluoxetine
Paroxetine
Others

May be at increased risk of respiratory depression

46
Q

DI with codeine?

A

Codeine undergoes conversion to morphine by 2D6 enzyme

47
Q

DI with Oxycodone and Methadone?

A

Metabolized by 3A4

48
Q

PDE-5 inhibitors

A

3A4 substrate

T4 avoid use with 3A4 inhibitor (inh metabolism leading to higher drug levels)

49
Q

Which meds have chelation risks?

A

Quinolones, Tetracyclines

50
Q

Which statins have the most risk of drug interaction?

A

LAS

Lovastation, Atorvastatin, Simvastatin

51
Q

Which drugs increase statin drug levels?

A

Gemfibrozil

Macrolides

52
Q

Which Calcineurin inhibitors are subject to significant rxn?

A

Tacrolimus and Cyclosporine

53
Q

List drugs that bleeding risk is a concern in

A

Anticoagulants (warfarin, Dabigatran, Rivaroxaban, heparin and others)

AND

Antiplatelets (aspirin, dipyridamole, Clopidogrel, prasugrel, ticagrelor)

54
Q

What dx condition may cause hyperkalemia risk?

A

Since potassium is renally cleared, severe renal dx causes hyperkalemia

55
Q

List drugs that should be avoided if potassium is high at baseline (> 5 mEq/L)

A

Spironolactone

Eplerenone

ACEI
ARBs
Aliskiren
Amiloride
Triamterene
Salt substitutes (KCL)
Drospirenone-containing OCPs
56
Q

List substances that may result in CNS depression

A 
Alcohol
Most pain meds (ALL opioids, some NSAIDs, other pain meds)
Skeletal muscle relaxants
Anticonvulsants
Benzodiazepines
Barbiturates
Hypnotics
Mirtazapine
Trazodone
Dronabinol
Nabilone
Propranolol
Clonidine
57
Q

List agents that may cuz QT prolongation and Torsades De Pointes

A

Mostly arrhythmia drugs and effect is additive

58
Q

List agents that may cuz Ototoxicity

A 
Salicylates
Vanco
Aminoglycosides
Cisplatin
Loop diuretics
59
Q

Which meds can also increase INR?

A

Amiodarone
Trimethoprim/Sulfamethoxazole (Bactrim)
Ketoconazole

60
Q

What do u need to separate Cipro from?

A

Multivitamin
Iron
Yogurt, cheese

61
Q

What meds can increase risk of arrhythmias?

A

Fluconazole
Erythromycin
Ziprasidone

62
Q

Primary location of CYP enzymes?

A

Liver and Intestines

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