Drug interactions Flashcards
Which drugs are strong CYP inhibitors?
G PACMAN
Grapefruit
Protease inhibitors (ritonavir)
Azales
Cyclosporine, Cobicistat
Macrolides
Amiodarone
Non DHP CCP
Which drugs are strong CYP inducers?
Phenytoin
Phenobarbital
Carbamazepine/Oxcarbamazepine
St. John’s Wart
Rifampin
Smoking
How do CYP inducers affect prodrugs?
They increase their action because of more conversion to active drug
How do CYP inducers affect CYP substrates?
They decrease the efficacy
Warfarin is a substrate for which CYP enzymes?
1A2
2C9
3A4
A 56 year old patient has a prescription of Vfend to treat his infection. His other medications include Zocor, Hydrochlorothiazide, and Kerlone eye drops. What changes would you make?
Voriconazole is and CYP inhibitor
Simvastatin is a CYP substrate
Their conmittent use is contraindicated
What are some common substrates of P-gp?
DOACs
Digoxin, Diltiazem (Cardizem), Verapamil (Calan)
Cyclosporine, Tacrolimus
HCV drugs
Colchicine (Colcrys) for gout
What are some common INDUCERS of P-gp?
Carbamazepine
Phenobarbital
Phenytoin
Rifampin
St. John’s Wart
What are some common INHIBITORS of P-gp?
Cobicistat, Ritonavir
Amiodarone, Diltiazem, Verapamil
Clarithromycin
Itraconazole
Posaconazole
A patient is on warfarin for mitral valve. Before the patient is started on Pacerone, what drug interactions might their be?
Amiodarone is a strong 2C9 inhibitor, increase INR and warfarin effect
A patient is started on Digox and Pacerone. What interaction might you expect from this combination?
Amiodarone is a P-gp inhibitor and Digoxin is a substrate. Starting dose of digoxin should be at 50% lower
**monitor for bradycardia
What might you expect with Lanoxin and Bumex use together?
Digoxin toxicity of hypokalemia is worsened with bumetanide (loop)
Which statins are CYP3A4 substrate?
Lovastatin (Altoprev)
SImvastin (Zocor)
Atorvastatin (Lipitor)
Which statins are CONTRAINDICATED with strong CYP3A4 inhibitors?
Lovastatin (Altoprev)
Simvastatin (Zocor)
Which opioids are CYP3A4 substrates?
Hydrocodone
Fentanyl
Oxycodone
Methadone
A patient was started on Duragesic in the hospital for pain. Other medications include: Cardiazem, Pacerone, and Crestor. Which medications cause a drug interaction with Duragesic?
-Cardiazem
-Pacerone
Both are strong CYP inhibitors and should NOT be used with opioids with that are CYP3A4 substrate
- Hydrocodone
- Oxycodone
- Methadone (Dolophine)
- Fentanyl
What two AED drugs need to be dose adjusted because of the drug interaction between them?
Valproate + Lamotrigine
***Decrease Lamotrigine dose!!!!!
What drugs are CONTRAINDICATED with MAO inhibitor use?
Drugs/food that increase Epi, DA, or NE
- SNRI
- TCAs
- Bupropion
- Levodopa
- Stimulants (methylphenidate, Lisdexamfetamine)
- tyramine right foods
Drugs that increase Serotonin:
-SSRI/SNRI
- TCAs
- Mirtazapine (Remeron)
- Trazadone (Desyrel)
- Opioids
Others: Lithium, St. John’s wort, dextromethorphan (Delsym)
Which drugs should be avoided with CYP2D6 inhibitor?
Tamoxifen (prodrug)
Codeine (prodrug)
Meperidine (Demerol)
Tramadol (prodrug)
What drugs are metabolized by cyp enzymes?
Oral contraceptives
AEDs (carbamazepine is auto-inducer)
What CYP enzyme does smoking have an effect on and how?
CYP1A2 inducer!
What drugs may need to be increased while patient is smoking?
Caffeine
Theophylline
Warfarin
Antipsychotics
Antidepressants
Hypnotics
Anxiolytics
A warfarin patient decides he would like to quit smoking. What might happen to the INR when the patient stops smoking?
increase INR because increase effect for warfarin
What should you do to the Theophylline dose if a patient stops smoking?
Decrease the dose! will have a greater effect!
