Drug Interactions

Question 1

What is Pharmacodynamics?

Answer 1

Effect or change that a drug has on the body or some other type of organism

Question 2

What does synergy mean?

Answer 2

Synergy occurs when 2 drugs taken in combo have a greater effect than that obtained by simply adding the two individual effects together

Question 3

What does Pharmacokinetics refer to?

What does chelation refer to ?

Answer 3

The effect or change that the body has on a drug as it goes through the ADME processes

when the drug binds to polyvalent cations in another compound

Question 4

Drugs with polyvalent cations or other binding properties such as? (which drugs?)

Should be separated from? (4 drugs)

Answer 4

antacids , MVI, Sucralfate, bile acid resins, aluminum, calcium, iron, mag, zinc, phosphate binders

Quinolones, tetracyclines, levothyroxine and oral biphosphonates

Question 5

If gastrointestinal pH is incr, what happens to absorption?

whats an example of this?

Answer 5

it decreases

acid suppressing drugs (H2ra’s, PPI’s) decr absorption of antifungals like itraconazole

Question 6

Metabolism primarily occurs where?

What about excretion?

What blocks the renal excretion of penicillin?

where are CYP450 enzymes primaryly expressed?

Answer 6

1. Usually in the liver
2. Renal excretion = primary route of drug excretion
3. probenecid
4. in the liver

Question 7

1. Codeine has a risk of toxicity with which pt population and why?
2. What if you’re a PM of CYP2D6 and you take morphine?
3. Why shouldnt you use Plavix with esopmerazole or omeprazole?

Answer 7

1. UMs of CYP2D6 due to more rapid conversion of morphine (do not use)
2. risk of poor analgesia
3. Bc plavix is a prodrug that’s metabolized to active form by CYP2C19 and those drugs r inhibitors of CYP2C19

Question 8

CYP Inhibitors: G<3PACMAN

What does it stand for?

Answer 8

grapefruit

protease inhibs (espeically ritonavir)

azole antifungals

Cyclosporine/Cobicistat

Macrolides (claritho, erythro, not azithro)

amiodarone (and dronedarone)

Non DHP CCBS

Question 9

CYP Inducers:
PS PORCS

What drugs does the pneumonic stand for?

Answer 9

Phenytoin

Smoking

Phenobarb

Oxcarbazepine

rifampin (and rifabutin, rifapentine)

carbamazepine

SJW

Question 10

Whats the difference in timing between enzyme inhibition and enzyme induction?

Answer 10

Inhibition: fast, effects seen within a few days and will end quickly when the inhibitor is discontinued

Inducer: Takes time. When inducer is stopped, it could take 2-4 weeks for induction effects to dissapear completely

Question 11

What do PGP efflux pumps/transporters do?

PGP pumps in the cell membranes of the GI tract do what?

When a drug blocks or inhibits PGP, a drug that’s a PGP substrate will?

Answer 11

1. They protect against foreign substances by moving them out of critical areas
2. transport drugs and their metabs out of the body by pumping them into the gut where they can be excreted into the stool
3. have increased absorption and the substrate drug level will increase

Question 12

What route does a drug take when it goes enterohepatic recycling?

what does this do to the drug?

Answer 12

1. after metabolism in liver, drug can be transported back through the bile back to the gut. from gut drug is rebasorbed in small intestine , enter into portal vein and travel back to liver
2. it increases the duration of action

Question 13

1. Which drug classes can have serotonergic toxicity when used together? (5)
2. Serotonin syndrome risk incr when?
3. Sx’s of serotonin syndrome:
   -Example of alt ment status?
   -Example of neuromuscular excitation?
4. recc eliminating an initial serotonergic drug prior to starting a new serotonergic drug by using a washout period of how long?

Answer 13

1. Antidepressants
   MAOI’s
   Opioids
   Triptans
   Natural products (SJW, L tryptophan)
   Others like buspar, lithium
2. 2 or more drugs that affect serotonin are used together
3. agitation
   -rigidity and seizures
4. 2 wks, or 5 weeks for fluoxetine

Question 14

For drugs that can cause hyperkalemia, what should you counsel patients on in regards to salt substitutes?

Answer 14

Avoid salt subs that contain KCl

Question 15

Which drug classes can have additive side effects that cause QT prolongation?

Answer 15

Antiarrhythmics (Class 1a, 1C and 3)

ANtinfectives
-Antimalarials (hydroxychloro)
-Azole antifungals
-macrolides
-quinolones

ANtideppressants
-SSRI’s
-TCAs

Antipsychs
-1st gen (Haldol , thioridazine)
-2nd gen highest w/ziprasidone

Antiemetics
-5Ht3 receptor antags (Zofran)

Onc Meds

Question 16

QT Prolongation:

1. Dosing of citalopram ?
2. Lexapro dosing?
3. For pt’s with CVD, which ssri is safest?
4. What should not be used for inpatient N/V?

Answer 16

1. dont exceed 40 mg daily or 20 mg daily in elderly (>60 yrs)
2. dont exceed 20 mg daily or 10 mg daily in elderly
3. sertraline
4. droperidol

Question 17

Which drugs/drug classes can have an additive effect of ototoxicity? (5)

Answer 17

Aminoglycosides (Gentamicin, tobramycin, amikacin)

cisplatin

loop diuretics

salicylates

vancomycin

Question 18

Which drugs/drug classes have additive side effect of nephrotoxicity? (6)

Answer 18

Anti-infectives
-Ag’s, amphotericin B, Polymyxins, vanco

Cisplatin

Calciuneurin Inhibs

Loop diuretics

NSAIDS

Radiographic contrast dye

Question 19

For cisplatin, what should be used to protect kidneys?

Answer 19

amifostine (ethyol)

Question 20

Which drugs/drug classes have anticholinergic toxicity? (6)

Answer 20

Antidepress/Anyipsychs (Paroxetine, TCA’s 1st gen antipsychs)

Sedating antihistamines

Centrally acting anticholinergics (Benztropine, trihexyphenidyl)

Muscle relaxants (Baclofen, carisoprodol, cyclobenzaprine)

Antimuscarinics for urinary incontinence
(Oxybutynin darifenacin, tolteridone)

Others:
Atropine, belladonna, Bentyl

Question 21

Kim see handheld flashcards for more DDI’s

Answer 21

study flashcards