A pharmacy student is completing a drug interaction screening for a patient with a new prescription for paroxetine, a known CYP enzyme inhibitor. The pharmacy student notes the effect of taking paroxetine with each of the following medications:

Carvedilol: effects of carvedilol will be increased
Tamoxifen: effects of tamoxifen will be decreasedTramadol: effects of tramadol will be decreased

Which of the following statements make the assessment above true? (Select ALL that apply.)

Tamoxifen is a prodrug, carvedilol is an active substrate, tramadol is a prodrug

Drug A is an active substrate of enzyme X. Drug B is an inhibitor of enzyme X. A patient has been using Drug A with good results. The patient has now started therapy with Drug B. The concentration of Drug A will:

Increase

(Drug A is an active substrate of enzyme X. An inhibitor of this enzyme will be added. Inhibitors knock out the ability of the enzyme to metabolize the drug, by various mechanisms such as changing the shape of the enzyme via binding or depletion of a co-factor required for metabolism. Without enough enzyme present, the concentration of substrates will increase as the liver breaks down less.)

Which of the following are CYP3A4 inhibitors?

Ritonavir, diflucan, grapefruit

A patient has an estimated creatinine clearance of 25 mL/min. Her potassium level is 4.8 mEq/L. Which of the following drugs will increase her risk of hyperkalemia and should be used with caution?

Enalapril

A patient who is a CYP450 2D6 rapid metabolizer is using codeine for pain. What effect will the 2D6 polymorphism have on the concentration of morphine?

The morphine concentration will increase

(The conversion of codeine to morphine is increased in rapid metabolizers of 2D6. Codeine should be avoided in women who are breastfeeding because often, the 2D6 variant is unknown. Morphine crosses readily into breast milk, and the infant could suffer fatal respiratory depression. Codeine is contraindicated in children under 12 years of age, and in children under 18 years of age after tonsillectomy and adenoidectomy.)

Which cytochrome P450 enzyme is not inducible?

2D6

Which drug/s can increase the QT interval? (Select ALL that apply.)

Quinolones, methadone and amitriptyline

Drug A is a substrate of CYP2C9 and a potent 3A4 inhibitor. Drug B is a substrate of 2D6 and 1A2 as well as a potent inhibitor of 2C19. Drug C is a substrate of 3A4 and a potent inhibitor of 2D6. If all three drugs were given together, what would the levels of each drug be expected to do?

Drug A levels would stay the same, Drug B levels would increase and Drug C levels would increase

(Drug C inhibits CYP2D6 and increases levels of Drug B (substrate of 2D6). Drug A inhibits 3A4 and increases levels of Drug C (substrate of 3A4). Neither Drug B nor Drug C inhibits or induces 2C9 and therefore, levels of Drug A remain the same.)

A patient with asthma, COPD and seizures has been using theophylline and valproate for many years. The patient has been under a lot of stress lately and has started smoking again. She smokes about 15-20 cigarettes daily. Which of the following statements is correct about smoking?

Smoking will decrease the theophylline level.

VN uses Imitrex for migraines 2-4 times each month. Recently she began to use Sarafem 10 mg daily for premenstrual dysphoric disorder. In addition, she uses Ultram once or twice daily for headache relief. She is at risk for the following symptoms: (Select ALL that apply.)

Agitation, rigidity

Which of the following drugs can cause hearing loss? (Select ALL that apply.)

Vancomycin, gentamicin, ethacrynic acid and salicylates can cause hearing loss, tinnitus or vertigo.

A patient is using digoxin. If he is prescribed the following drug, the digoxin serum concentration will increase:

Verapamil

(Verapamil is a P-gp inhibitor, and digoxin is a P-gp substrate. )

A patient with atrial fibrillation has been using warfarin for nine months, and his INR is stable around 2.3. The patient has been diagnosed with depression and asked for a prescription that will not interact with his other medications. Which of the following drugs will not increase the bleeding risk in this patient?

Wellbutrin

Clopidogrel is a prodrug metabolized by CYP2C19. What effect will a CYP2C19 inhibitor have?

Decreased antiplatelet effect immediately

Chief Complaint: shortness of breath

History of Present Illness: SZ is a 77-year-old female admitted to the hospital on April 7th for worsening shortness of breath that she describes as much worse than her "typical heart failure episodes." In addition, SZ states that she has been experiencing episodes of nausea and blurry or double vision over the past couple of weeks.

Allergies: penicillin (rash and lip swelling)

Past Medical History: COPD, heart failure (last EF 30%), alcoholism

Home Medications: Altace 10 mg daily, Lasix 40 mg BID, Coreg CR 40 mg daily, Digox 0.25 mg daily, Combivent Respimat 1 inhalation QID, Procardia XL 60 mg daily, Aldactone 25 mg daily

SZ should be counseled to avoid drinking grapefruit juice to prevent increased levels of which medication?

Procardia XL

( same case as above) During her hospital stay, SZ develops atrial fibrillation. What adjustment should be made to her home medications if amiodarone is added to her regimen?

Decrease digoxin to 0.125 mg daily

A patient is at risk for atrial fibrillation; she has had atrial fibrillation in the past. The medical team has asked the pharmacist to check for drugs on her profile that can increase her risk of arrhythmia. The pharmacist should include which of the following medications?

Ziprasidone

Which of the following are inhibitors of CYP450 3A4?

Voriconazole (Vfend), clarithromycin ( Biaxin), diltiazem ( Cardizem) and grapefruit (juice and fruit) are all CYP3A4 inhibitors.

Chief Complaint: "I'm here for my flu vaccine but my stomach hurts"
History of Present Illness: ZB is a 66-year-old white female who presents to her PCP with a 2-week history of gastric pain that is worse at night and in between meals. She describes a burning pain that goes from a "9 out of 10" to a "5 out of 10" when she eats.
Allergies: penicillin (swollen tongue)
Past Medical History: hypertension, type 2 diabetes, dyslipidemia, osteoporosis, anxiety, chronic pain
Social History: quit smoking 20 years ago (previous 15-year pack history), drinks 1 vodka and soda each night while playing cards with friends at the retirement home
Medications:
Hydrochlorothiazide 12.5 mg PO dailyNorvasc 10 mg PO dailyCrestor 10 mg PO dailyCaltrate 600+D3 1 tablet PO BIDIbandronate PO as instructed
Glucophage 1 gram PO BIDQsymia (takes daily, cannot recall dose)Hydrocodone/acetaminophen 7.5/300 mg PO Q6H PRN Klonopin 0.5 mg PO BID PRNFexmid 10 mg TID PRN

CNS depression

Which of the following are P-gp substrates?

Important P-gp substrates include the calcineurin inhibitors tacrolimus and cyclosporine, colchicine, and the anticoagulants dabigatran, apixaban and rivaroxaban.

BH takes an estrogen and progestin combination oral contraceptive (COC). She recently received a prescription for phenytoin. Which of the following best describes the interaction between these medications?

Phenytoin is a potent inducer. Inducers result in higher levels of CYP enzymes, which decrease levels of substrate drugs (e.g., estrogen).

Drug metabolism occurs most often through which CYP450 enzyme?

3A4

Theophylline is a substrate of CYP1A2. A patient on long-term theophylline, who has been well-controlled with infrequent use of her rescue inhaler, has developed a UTI that is difficult to treat. The physician prescribed a 7-day course of ciprofloxacin. Which of the following is most likely to occur?

Possible theophylline toxicity

A 74-year-old woman had been taking metoprolol succinate 100 mg daily, warfarin 4 mg daily and amitriptyline 50 mg QHS for several years. Shortly after the death of her spouse, she experienced some depression and was prescribed citalopram 40 mg daily. The patient is most at risk for:

Torsade de Pointes

Drug A is an active drug substrate of enzyme X. Drug B is an inducer of enzyme X. A patient has been using Drug A with good results. The patient has now started therapy with Drug B. The concentration of Drug A will:

Decrease

(Drug A is a substrate of enzyme X, which is being induced by another drug. That means the other drug (Drug B) is causing more enzyme X to be produced. More of the enzyme will result in more metabolism of Drug A, and the concentration will decrease.)

Phosphodiesterase inhibitors (e.g., tadalafil) cannot be used safely with nitrates. What is most likely to happen if a pharmacist misses this interaction?

Acute drop in blood pressure

GV has been using a monoamine oxidase inhibitor to help control her depression for many years. She is careful to check that other drugs and foods do not interact with her medicine. Which of the following drugs should be avoided with GV's antidepressant? (Select ALL that apply.)

Methylphenidate and claritin-D

Select the correct statements concerning the drug interaction between valproic acid and lamotrigine. (Select ALL that apply.)

• Valproic acid inhibits lamotrigine metabolism
• This interactions increases the risk for severe lamotrigine induced rash
• When using these two together, the appropriate Lamicital starter kit should be used

Cyclosporine is an inhibitor of the P-glycoprotein (P-gp) efflux transporter. If a drug is a substrate of P-gp, what will happen to the drug concentration if it is given to a patient receiving cyclosporine?

The concentration of the substrate will increase

A 65-year-old woman brings a new prescription for a monoamine oxidase inhibitor to the pharmacy. Which of the following foods should she be counseled to avoid?

Sauerkraut

A patient with atrial fibrillation has been using warfarin for four months, and his INR is stable around 2.3. Select the interaction that can occur with the addition of these other medications:

If naproxen is added, the INR may or may not increase and the bleeding risk will be elevated

Which of the following is an inducer of CYP450 3A4?

Phenobarbital, pacerone

History of Present Illness: BG is a 71-year-old male who presents to the hospital with a 6-day history of non-bloody diarrhea that he believes may be a side effect of donepezil. He has had no sick contacts or changes to his usual diet. He denies fever, sweating, chills, chest pain, shortness of breath, nausea or vomiting.
Allergies: NKDA
Past Medical HistoryParkinson disease (diagnosed 6 weeks ago)Atrial fibrillationMitral valve repair (bioprosthetic valve)Cerebrovascular accidentModerate-severe Alzheimer's diseaseAnkylosing spondylitisCholecystectomyArthroscopy of the right knee
Social HistoryDrinks 1-2 glasses of wine with his wife about 5 times a week.
Home Medications Sinemet 25/100 mg PO four times dailyDonepezil 5 mg PO dailyFinasteride 5 mg PO daily
Cogentin 1 mg PO QHSMidodrine 5 mg PO dailyWarfarin 5 mg PO daily
Cyanocobalamin 1,000 mcg PO dailyDofetilide 250 mcg PO BIDFludrocortisone 0.1 mg PO

The effects of warfarin will increase

(same case from above) While verifying medication orders, the pharmacist receives an alert about a medication that is a CYP1A2 inhibitor. Which medication, from home or newly ordered on admission, meets this criteria?

Cipro

Which of the following drugs interacts with grapefruit?

Tacrolimus

Which of the following statements best describes warfarin metabolism?

Warfarin is racemic; the S-isomer is more potent and is primarily a substrate of CYP2C9

TW has been taking phenelzine (Nardil) for many years to treat depression. Which drug will interact with TW's antidepressant?

Tramadol

Drug A is a substrate of enzyme X. Drug A is also an inducer of enzyme Y. Drug B is a substrate of enzyme Y. Drug B is also an inhibitor of enzyme X. When these drugs are both administered, what will happen to the concentrations of Drug A and Drug B?

Levels of drug A will increase and levels of drug B will decrease

(Drug A is a substrate of an enzyme that is being inhibited and Drug B is a substrate of an enzyme that is being induced.)

CL is being placed on the waiting list for a kidney transplant. She has a creatinine clearance of 22 mL/min and experiences frequent bouts of hyperkalemia. Which medications elevate potassium and would put her at risk for arrhythmia? (Select ALL that apply.)

Eplerenone, yasmin, aldactone

A patient with a deep vein thrombosis has been using warfarin for four months, and his INR is stable around 2.5. Which of the following interactions is correct?

If rifampin is added, the INR will decrease

(CYP2C9 inducers (which decrease the INR) include phenobarbital, phenytoin, primidone, rifampin (large decrease in INR) and St. John's wort.)

Which of the following are CYP450 enzyme inducers? (Select ALL that apply.)

Phenytoin, oxcarbazepine, carbamazepine and St. John's wort are CYP450 enzyme inducers. Neoral is cyclosporine, which is a CYP450 enzyme inhibitor.

Which of the following drugs increase the risk of a patient having a fall that could result in injury? (Select ALL that apply.)

Muscle relaxants, mirtazapine and benzodiazepines are central nervous system (CNS) depressants. CNS side effects are caused by drugs that enter the CNS (lipophilic) and result in sedation (somnolence), dizziness, confusion (decreased cognitive function) and altered consciousness.

Which medication must have the dose reduced by 30-50% if amiodarone is added to the same patient profile?

Warfarin

(The dose of warfarin should be decreased by 30-50% when beginning amiodarone.)

LD is a 74-year-old African American female who is being admitted to a nursing home. Her family can no longer care for her at home due to increasing episodes of urinary incontinence.
Allergies: NKDA

Past Medical History: dementia, hypertension, osteoporosis, type 2 diabetes, incontinence

Medications:
Glyburide 5 mg daily
Ditropan XL 10 mg daily
Norvasc 10 mg daily
Prolia 60 mg SC (last administration on January 7th)
Mirapex 0.125 mg QHS
Hydrochlorothiazide 12.5 mg daily
Toprol XL 50 mg daily
Aricept 5 mg daily
Zoloft 100 mg daily

The nursing home admitting orders for LD include Ultram 50 mg PO Q4H as needed for pain. The pharmacist verifying the order receives a drug interaction alert warning of an increased risk of:

Serotonin syndrome

A major drug interaction can occur with the use of grapefruit juice and which of the following medications?

Lovastatin and nifedipine

What can occur if a CYP450 3A4 inhibitor is given to a patient on oxycodone? (Select ALL that apply.)

Respiratory depression and sedation

MT is taking Aggrenox, torsemide, Crestor, Toprol XL, Lotensin, Cardizem, Klor-Con, Nitrostat PRN, fish oil and DHEA. Based on his medication list, MT is most at risk for:

Bradycardia

A patient with atrial fibrillation has been using warfarin for nine months, and his INR is stable between 2.3-2.7. What is most likely to occur if he starts taking ginkgo biloba?

The INR will stay at about the same and the bleeding risk will increase

Which of the following statins has the lowest risk of drug interactions?

Pravastatin

(Atorvastatin, lovastatin, simvastatin and fluvastatin are all metabolized by CYP450 enzymes. When taken with an inhibitor, the risk of myopathy is increased. In severe cases, rhabdomyolysis can occur, which may lead to acute renal failure. To avoid this interaction, recommend a statin not metabolized by CYP450 enzymes (e.g., pravastatin, rosuvastatin).)

Which of the following drugs can cause hearing loss? (Select ALL that apply.)

Loop diuretics, vancomycin, aminoglycosides, cisplatin and salicylates are drugs that can cause ototoxicity.