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Top 100 Drug Interactions > Top 100 Drug Interactions > Flashcards

Top 100 Drug Interactions Flashcards

1
Q

N-acetylcysteine

A

No clinically significant drug interactions

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2
Q

Acetaminophen

A

CYP inducers (PS PORCS)- such as phenytoin and carbamazepine- increase rate of NAPQI production/liver toxicity, after acetaminophen overdose

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3
Q

acyclovir

A

Probenecid and interferon increase acyclovir concentrations.

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4
Q

adenosine

A

Dipyridamole blocks cellular reuptake of adenosine. Theophylline is a competitive agonist at adenosine receptors.

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5
Q

epinephrine

A

Beta-blockers can induce widespread vasoconstriction.

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6
Q

Aldosterone antagonists

A

ACE inhibitors; ARBs and other K-elevating drugs/supplements increase hyperkalemia risk.

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7
Q

Antacids/alginates

A
  • Divalent ions reduce serum concentration of drugs such as bisphosphonates, levothyroxine, tetracyclines, digoxin, and PPIs. Take antacid either 4 hours before or 2 hours after taking this medication.
  • Antacids increase the alkalinity of urine and so increase lithium and aspirin excretion.
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8
Q

Albendazole

A
  • Plasma concentrations are lowered by phenytoin and carbamazepine.
  • Cimetidine increases albendazole concentration.
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9
Q

Allopurinol

A
  • Toxicity risk of mercaptopurine/azathioprine increases because allopurinol inhibits xanthine oxidase.
  • Amoxicillin increases skin rash risk.
  • ACE inhibitors and thiazide diuretics increase the risk of hypersensitivity reactions.
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10
Q

Alpha blockers

A
  • Other blood pressure-lowering drugs increase the risk of first-dose hypotension and hypotension risk generally thereafter.
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11
Q

Aminoglycosides

A
  • Loop diuretics/vancomycin increase ototoxicity risk.

- Cyclosporine, platinum chemotherapy, cephalosporins, and vancomycin increase kidney toxicity risk.

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12
Q

Aminosalicylates (sulfasalazine, mesalazine, olsalazine, balsalazide)

A
  • PPIs increase gastric pH and so may affect gastric coating of aminosalicylates.
  • Lactulose reduces stool pH and so can prevent 5-ASA release into the intestine.
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13
Q

Amiodarone

A

Amiodarone increases the plasma concentration of digoxin, diltiazem and verapamil (increasing risk of AV block, bradycardia and heart failure)

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14
Q

ACE inhibitors/ARBS

A
  • Hyperkalemia risk increases when taken with other K-elevating drugs/supplements.
  • Renal failure risk increases when taken with NSAIDs.
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15
Q

Amphotericin B

A
  • Increased risk of flucytosine toxicity
  • Increased renal toxicity with cisplatin/diuretics
  • Increased risk of hypokalemia with corticosteroids
  • Renal damage with aminoglycosides/other nephrotoxic drugs
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16
Q

Antidepressants

A
  • Serotonin syndrome with taken with other serotonergic drugs, such as MAO inhibitors.
  • TCAs augment antimuscarinic and sedative effects of other drugs.
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17
Q

Antiemetics: H1 antagonists (diphenhydramine, meclizine, promethazine, doxylamine succinate)

A
  • Sedation risk increases when taken with other sedative drugs (benzos, etc.)
  • Anticholinergic effects are more pronounced when taken with ipratropium/tiotropium
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18
Q

Antiemetics (prochlorperazine, chlorpromazine)

A
  • QT prolongation risk increases when taken with antipsychotics, quinine, SSRIs, macrolides, fluoroquinolones, and ciprofloxacin
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19
Q

Antifungal Drugs: fluconazole

A
  • Fluconazole inhibits CYP enzymes- increasing plasma concentration of phenytoin, carbamazepine, warfarin, simvastatin, and sulfonylureas.
  • Reduces the antiplatelet effect of clopidogrel.
  • Risk of arrhythmias increases with taken with QT-prolonging drugs.
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20
Q

Antihistamines (H1 antagonists)
1st gen: diphenhydramine (Benadryl) and hydroxyzine (Vistaril/Atarax)
2nd gen: fexofenadine (Allegra), loratadine (Claritin), cetirizine (Zyrtec)

A
  • No major drug interactions.
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21
Q

Loperamide

A

P-glycoprotein inhibitors (quinidine, ritonavir, ketoconazole) increase loperamide levels.

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22
Q

Antimuscarinics (cardiovascular: atropine, hyoscine butylbromide)
(genito-urinary: oxybutynin, tolterodine, solifenacin)

A
  • Antimuscarinic effects more pronounced when taken with other drugs with the same effects, such as tricyclic antidepressants.
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23
Q

Antipsychotics: typical and atypical drugs

A

Avoid with QT-prolonging drugs. Avoid with dopamine-blocking antiemetics.

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24
Q

Aspirin

A

Antiplatelet and anticoagulant drugs increase bleeding risk.

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25
Q

Benzodiazepines

A
  • Sedative risk increases with other sedation-causing drugs and substances, including alcohol and opioids.
  • CYP inhibitors- such as macrolides, fluconazole, amiodarone, and protease inhibitors- increase their effects.
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26
Q

Beta-2 agonists (isoprenaline, albuterol, fenoterol, terbutaline, salmeterol, formoterol)

A
  • Beta-blockers reduce their effectiveness.

- Corticosteroids increase the risk of hypokalemia.

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27
Q

Beta blockers

A

Avoid with non-dihydropyridine calcium channel blockers- such as verapamil and diltiazem- as the combination can lead to bradycardia, heart failure, and asystole.

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28
Q

Bisphosphonates

A

Divalent ions reduce drug absorption. (ex, antacids, iron)

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29
Q

Calcium

A
  • Oral calcium reduces the absorption of bisphosphonates, tetracyclines, and levothyroxine
  • Avoid with Na bicarbonate when taken IV to eliminate risk of precipitation.
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30
Q

Carbamazepine (CYP 450 inducer)

A
  • Induces CYP 450 enzymes to reduce the concentration of drugs such as warfarin, progestogens, and estrogens.
  • Drugs that lower the seizure threshold- such as TCAs, SSRIs, and tramadol- reduce the efficacy of anticonvulsant medicines.
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31
Q

Cephalosporins:

Carbapenems:

A
  • Enhance the anticoagulant effect of warfarin.
  • Increase nephrotoxicity of aminoglycosides.
  • Carbapenems reduce the efficacy of valproate.
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32
Q

Clopidogrel (Prodrug): CYP3A4; CYP2C19

A
  • CYP 450 inhibitors block its activation- omeprazole, erythromycin, antifungals, SSRIs, etc.
  • Lansoprazole/pantoprazole is preferred if gastroprotection is needed.
  • Risk of bleeding increases with antiplatelet, anticoagulant drugs, and NSAIDs.
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33
Q

Corticosteroids

Systemic: prednisolone hydrocortisone, dexamethasone

A
  • NSAIDs increase the risk of peptic ulceration/bleeding.
  • Risk of hypokalemia when taken with B2-agonists, loop, or thiazide diuretics.
  • Efficacy is reduced by CYP inducers such as phenytoin and rifampin.
  • Corticosteroids reduce immune response to vaccines.
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34
Q

Cyclophosphamide

A
  • Rifampin and phenytoin accelerate the metabolism of cyclophosphamide into active metabolites.
  • Corticosteroids/TCAs /allopurinol slow the conversion of cyclophosphamide to its metabolites, reducing therapeutic and toxic effects.
  • Prolongs with neuromuscular blockade with succinylcholine.
  • Tricyclic antidepressants lead to delayed bladder emptying, increasing acrolein accumulation, and risk of bladder bleedings.
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35
Q

Digoxin

A
  • Digoxin toxicity increases when taken with loop or thiazide diuretics, amiodarone, calcium channel blockers, spironolactone, and quinine
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36
Q

Dipyridamole- inhibits cellular reuptake of adenosine.

A

Bleeding risk increases when taken with antiplatelet or anticoagulant medicines.

37
Q

Diuretics

A
  • Loop diuretics reduce lithium excretion.
  • Due to diuretic-linked hypokalemia, digoxin toxicity risk increases.
  • Increase the risk of ototoxicity/nephrotoxicity when taken with aminoglycosides.
38
Q

Diuretics- Potassium-sparing (amiloride)

A
  • Avoid potassium-elevating drugs/supplements

- Renal clearance of lithium/digoxin reduced.

39
Q

Dopaminergic drugs (Parkinson’s disease: levodopa, ropinirole, pramipexole)

A
  • Due to opposing effects on dopamine receptors, dopaminergic drugs should not be taken with antipsychotics (particularly with typical antipsychotics)
40
Q

Fibrates (fenofibrate):

A
  • Bile acid sequestrants (eg. cholestyramine) bind to fenofibrate, reducing absorption.
  • Increased risk of renal dysfunction with cyclosporine.
  • Increased risk of bleeding with warfarin.
  • Increased risk of myopathies with statins.
41
Q

Fibrinolytic drugs (alteplase, tenecteplase)

A
  • Antiplatelet drugs/anticoagulants increase the risk of bleeding.
  • ACE inhibitors increase the risk of anaphylactoid reactions.
42
Q

Flucytosine

A
  • Anticancer drug cytarabine inhibits the antimycotic effects of flucytosine.
  • Increases toxicity of amphotericin B.
43
Q

Fluoroquinolones

A
  • Divalent ions reduce absorption/efficacy.
  • Ciprofloxacin increases theophylline toxicity risk.
  • NSAIDs reduce the risk of seizures.
  • Prednisolone increases tendon rupture risk.
  • QT-prolonging drugs increase QT- prolongation risk and arrhythmia risk.
44
Q

Gabapentin/pregabalin

A
  • Sedative effects are enhanced when taken with other sedative-inducing drugs, such as opioids and benzodiazepines.
45
Q

Heparins

A
  • Antithrombotic drugs increase the risk of bleeding.
46
Q

Insulin

A
  • Taking insulin with systemic corticosteroids increases insulin requirements.
47
Q

Iron

A
  • Reduces absorption of levothyroxine, bisphosphonates, and tetracyclines.
48
Q

Isoniazid

A
  • Increases acetaminophen toxicity.
  • Decreases metabolism of carbamazepine.
  • Increases valproate levels.
49
Q

Isotretinoin

A
  • Vitamin A supplements increase toxicity risk.

- Increased risk of pseudotumor cerebri if taken with tetracyclines (“false brain tumor”)

50
Q

Bulk-forming (osmotic, stimulant)

A

Effective of warfarin slightly increased when taken with osmotic laxatives.

51
Q

Lidocaine

A

Epinephrine prolongs local anesthetic effect.

52
Q

Linezolid

A
  • Increased risk of serotonin syndrome if taken with MAO inhibitors or other serotonergic drugs.
53
Q

Macrolides

A
  • Clarithyromycin/erythromycin inhibit CYP 450 enzymes (but not azithromycin)- increasing bleeding risk with drugs such as warfarin, and myopathy risk with statins. QT prolongation risk increases when taken with other QT prolonging drugs- quinine, amiodarone, antipsychotics, SSRIs, fluroquinolones, etc.
54
Q

Metformin

A
  • IV contrast media increases risk of renal impairment, metformin accumulation and lactic acidosis.
  • Prednisolone and diuretics (loop/thiazide) reduce efficacy of metformin.
  • Drugs that impair renal function increase risk of metformin accumulation (NSAIDs, ACE inhibitors, etc.)
55
Q

Methotrexate

A
  • Penicillins and NSAIDs inhibit renal excretion.
  • Trimethoprim and phenytoin increase risk of hematological adverse effects.
  • Neutropenia risk increases with clozapine.
  • Probenecid inhibits methotrexate excretion.
56
Q

Metronidazole

A
  • Increases risk of bleeding with warfarin.
  • Increases risk of toxicity of phenytoin.
  • Increases risk of toxicity of lithium.
57
Q

Naloxone

A
  • Antagonizes the effect of opioids.
58
Q

Bupropion

A

CYP 450 inhibitors- such as valproate- increase bupropion concentration.
CYP 450 inducers- phenytoin, carbamazepine, reduces bupropion levels.

59
Q

Nitrates

A
  • Concurrent use of nitrates with PDE5 inhibitors, such as sildenafil, can cause pronounced hypotension.
  • Hypotensive effects augmented by other antihypertensive drugs.
60
Q

NSAIDs

A
  • Aspirin, corticosteroids: GI ulceration
  • Anticoagulants, SSRIs: GI bleeding
  • Renal impairment- ACE inhibitors, diuretics
  • NSAIDs increase bleeding risk of warfarin.
61
Q

Estrogens:
Progestogens:

A

CYP 450 inducers- such as rifampin- reduce the efficacy of hormonal contraception (higher risk with progestogen-only formulations).

62
Q

Opioids

A
  • Other sedating drugs- benzodiazepines, antipsychotics, Z-drugs, and TCAs- increase risk of sedation.
  • Tramadol should be avoided with drugs that lower the seizure threshold (eg. SSRIs, TCAs)
63
Q

Penicillins

A
  • Reduce renal elimination of methotrexate, increasing toxicity risks.
  • Enhance anticoagulant effect of warfarin by killing gut flora that orginarily produce vitamin K.
64
Q

Phenytoin

A

As an enzyme inducer, phenytoin reduces plasma concentration of warfarin, estrogens, and progestogens. Adverse effects of phenytoin increased by CYP inhibitors such as fluconazole, amiodarone, and diltiazem. Efficacy of phenytoin reduced by drugs that lower that seizure threshold (eg, SSRIs, antipsychotics, tramadol)

65
Q

PDE5 inhibitors (sildenafil, tadalafil)

A
  • Concurrent use with nitrates produces pronounced vasodilation/hypotension.
  • Caution required with vasodilators such as alpha-blockers and calcium channel blockers due to these combined hypotensive risks.
  • CYP inhibitors- fluconazole, amiodarone and diltiazem- increase plasma concentration of PDE5 inhibitors.
66
Q

Potassium- oral

A

Additive effects with other potassium-elevating drugs/supplements- such as ACE inhibitors, ARBs, potassium-sparing diuretics, IV potassium chloride, and aldosterone antagonists.

67
Q

Propofol

A
  • Respiratory effects are enhanced with taken with other drugs that cause respiratory depression, such as benzodiazepines and opioids.
68
Q

PPIs (lansoprazole, pantoprazole, omperazole)

A
  • Omeprazole reduces antiplatelet effect of clopidogrel by reducing its activation by CYP enzymes. Other PPIs are not associated with this drug interaction.
69
Q

Quinine

A
  • Increased risk of QT prolongation witih other QT-prolonging drugs- macrolides, fluoroquinolones, amiodarone, antipsychotics, and SSRIs.
70
Q

Most powerful inducer of CYP 450 enzymes- incresing metabolism of many medicines. Reduces effectiveness of antiretroviral drugs, atorvastatin, clarithromycin, voriconazole, rosiglitazone, and lorazepam, among many others.

Reduces efficacy of…

A

birth control pills or hormonal contraception.

71
Q

Ritonavir

A

Inhibits CYP 1A2 and induces CYP 3A4/2D6- meaning it is linked to many drugs interactions. It is used as an inhibitor to “boost” the clinical effects of other protease inhibitors.

72
Q

Statins (simvastatin, atorvastatin, pravastatin)

A
  • Metabolism reduced by CYP inhibitors such as amiodarone, itraconazole, macrolides, protease inhibitors- increasing the risk of myopathy-like adverse effects.
73
Q

Sulfonylureas (gliclazide)

A
  • Risk of hypoglycemia with metformin, thiazolidinediones (eg. pioglitazone), and insulin.
  • Efficacy reduced by drugs that elevate blood glucose such as prednisolone, loop and thiazide diuretics.
74
Q

Tetracyclines (minocycline, tetracycline, doxycycline)

A
  • Divalent ions reduce absorption/efficacy.

- Reduce anticoagulant effect of warfarin.

75
Q

thiamazole (methimazole)

A

Increased anticoagulant effect of warfarin.

76
Q

Thiazolidinediones (pioglitazone)

A
  • Hypoglycemia risk when taken with other anti-diabetic drugs.
  • Efficacy reduced by drugs that elevate blood glucose such as prednisolone, loop and thiazide diuretics.
77
Q

Thyroid hormones (levothyroxine):

A
  • Absorption reduced by antacids, calcium or iron salts.
  • Phenytoin/carbamazepine increase its metabolism.
  • Levothyroxine enhances the effects of warfarin.
78
Q

Trimethoprim

A
  • Potassium-elevating drugs increase the risk of hyperkalemia.
  • Folate antagonists (eg. methotrexate) and drugs that enhance folate metabolism (eg, phenytoin) increase risk of hematological adverse effects.
  • Trimethoprim enhances the anticoagulant effect of warfarin.
79
Q

Vaccines

A

Immunosuppressive drugs, including systemic corticosteroids, dampen the immunological response to vaccines and, in the case of live vaccines, may confer generalised infection.

80
Q

Valproate

A
  • Inhibits CYP 450 enzymes, increasing toxicity of warfarin and other antiepileptics.
  • Risk of seizures increases when valproate is taken with phenytoin/carbamazepine/carbapenems.
  • Adverse effects of valproate increased by macrolides and protease inhibitors.
  • Aspirin displaces valproate form protein binding sites.
  • Efficacy of valproate reduced by drugs that lower the seizure threshold.
81
Q

Vancomycin

A
  • Risk of ototoxicity/nephrotoxicity increases when vancomycin is taken with loop diuretics, aminoglycosides or cyclosporine.
82
Q

Warfarin

A
  • CYP 450 inhibitors (macrolides, protease inhibitors) increase bleeding risk.
  • Inducers (phenytoin and rifampin) increase warfarin metabolism and therefore increase the risk tof clot formation.
83
Q

Z-drugs (zaleplon, zolpidem, zopiclone)

A
  • Sedative effects of alcohol, benzodiazepines, opioids and antihistamines is enhanced.
  • Hypotensive effect of antihypertensive drugs is enhanced.
  • P450 inhibitors (macrolides) enhance sedative effects of Z-drugs.
  • P450 inducers (rifampin) impair sedation.
84
Q

5-HT4 antagonists (sumatriptan, zolmitriptan)

A

Serotonergic drugs- including MAO inhibitors- increase the risk of serotonin syndrome.

85
Q

Main CYP Inducers: PS PORCS

A
  • Phenytoin (Dilantin)
  • Smoking
  • Phenobarbital (Luminal)
  • Oxcarbazepine (Trileptal); eslicarbazepine (Aptiom)
  • Rifampin (Rifadin)
  • Carbamazepine (Tegretol)
  • St. John’s Wort
86
Q

Main Inhibitors (G-Pacman)

A
  • Grapefruit
  • Protease Inhibitors
  • Azole Antifungals
  • Cyclosporine (Neoral/Sandimmune); Cimetidine (Tagamet)
  • Macrolide ABXs (except azithromycin)
  • Amiodarone (Nexterone/Pacerone)
  • Non-DHP CCB’s [Diltiazem (Cardizem); Verapameil (Calan)]
87
Q

P-gp Substrates: Don’t Touch A Rabid Dog

A
  • digoxin (Lanoxin)
  • tacrolimus (Prograf)
  • apixaban (Eliquis)
  • rivaroxaban (Xarelto)
  • dabigatran (Pradaxa)
88
Q

MAOIs have a multitude of interactions. These are a few exceptions that do not interpret with MAOIs. A safe bet is to know the drugs that don’t interact, then assume all the other drugs do.

Drugs ok with MAOIs: IMALE

A
  • Ibandronic acid (Boniva)- osteoporosis
  • Metoprolol succinate (Toprol XL)
  • Alprazolam (Xanax)
  • Latanoprost (Xalatan)- glaucoma
  • Estrogen (Prempro)- oral contraceptive
89
Q

Increase digoxin levels: QVC Monthly Installment PaymentS

A
  • quinidine (Quinidex)
  • verapamil (Calan)
  • cycloporine (Neoral/Sandimmune)
  • macrolides (Mycins)
  • itraconazole (Sporanox)
  • propafenone (Rythmol)
  • spironolactone (Aldactone)

Top 100 Drug Interactions (2 decks)

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