Drug Interactions - Pharmacy Technician Certification Exam Ptce

1. What interaction occurs when warfarin is taken with trimethoprim-sulfamethoxazole (TMP-SMX)?

   Increased INR and bleeding. TMP-SMX inhibits CYP2C9 metabolism of warfarin, elevating its levels and anticoagulant activity.

2. What is the major drug-disease interaction for NSAIDs in patients with peptic ulcer disease?

   Worsened ulcer/GI bleeding. NSAIDs inhibit protective prostaglandins in the gastric mucosa, exacerbating ulceration and hemorrhage in susceptible individuals.

3. What is the major drug-disease interaction for metformin in severe renal impairment?

   Lactic acidosis risk. Renal impairment reduces metformin clearance, leading to accumulation and inhibition of mitochondrial respiration.

4. What is the major drug-supplement interaction between warfarin and St. Johns wort?

   Decreased INR (reduced warfarin effect). St. John's wort induces CYP3A4 and CYP2C9 enzymes, accelerating warfarin metabolism and reducing its efficacy.

5. What is the major drug-disease interaction for NSAIDs in chronic kidney disease?

   Worsened renal function. NSAIDs reduce prostaglandin-mediated renal vasodilation, decreasing glomerular filtration rate in compromised kidneys.

6. What severe interaction occurs when an MAOI is combined with SSRIs, SNRIs, or linezolid?

   Serotonin syndrome. MAOIs prevent serotonin breakdown, while these agents increase serotonin release or block reuptake, causing excess accumulation.

7. What is the major interaction when simvastatin or lovastatin is combined with clarithromycin?

   Increased statin levels; myopathy/rhabdomyolysis. Clarithromycin inhibits CYP3A4, impairing metabolism of these statins and elevating their plasma concentrations.

8. What is the major interaction when ACE inhibitors are taken with potassium supplements or potassium-sparing diuretics?

   Hyperkalemia. ACE inhibitors reduce potassium excretion, and combining with potassium-retaining agents exacerbates this effect.

9. What is the major interaction when digoxin is taken with amiodarone or verapamil?

   Increased digoxin levels/toxicity. Amiodarone and verapamil decrease renal clearance and displace digoxin from tissue binding, raising its serum levels.

10. What is the major interaction risk when warfarin is taken with NSAIDs (for example, ibuprofen)?

    Increased bleeding risk. NSAIDs inhibit platelet aggregation and can displace warfarin from protein binding sites, potentiating its anticoagulant effects.

11. What serious drug-drug interaction occurs when nitrates are combined with sildenafil (or other PDE-5 inhibitors)?

    Severe hypotension. Nitrates and PDE-5 inhibitors both cause vasodilation via the nitric oxide pathway, leading to synergistic hypotensive effects.

12. What is the major drug-disease interaction for nonselective beta-blockers (for example, propranolol) in asthma?

    Bronchospasm/worsened asthma. Nonselective beta-blockers antagonize beta-2 receptors in the airways, precipitating bronchoconstriction in asthmatic patients.

13. What is the major interaction when simvastatin or lovastatin is taken with grapefruit juice?

    Increased statin levels; myopathy risk. Grapefruit juice inhibits CYP3A4, reducing statin metabolism and increasing systemic exposure.

14. What is the major drug-supplement interaction between warfarin and ginkgo biloba?

    Increased bleeding risk. Ginkgo biloba inhibits platelet aggregation, synergizing with warfarin's anticoagulant effects.

15. What is the major interaction when lithium is combined with NSAIDs, ACE inhibitors, or thiazide diuretics?

    Increased lithium levels/toxicity. These drugs decrease renal lithium clearance by affecting sodium and fluid balance in the kidneys.

16. What is the key interaction between oral fluoroquinolones and aluminum/magnesium antacids or iron supplements?

    Reduced absorption (chelation). These metal ions chelate with fluoroquinolones, forming complexes that are poorly absorbed from the intestine.

17. What is the major interaction when warfarin is taken with amiodarone?

    Increased INR and bleeding. Amiodarone inhibits CYP2C9 and CYP3A4, reducing warfarin metabolism and enhancing its anticoagulant effects.

18. What drug-drug interaction occurs when opioids are combined with benzodiazepines?

    Additive CNS/respiratory depression. Both classes depress the central nervous system and respiratory drive through GABAergic and opioid receptor mechanisms.

19. What is the major interaction when metronidazole is taken with alcohol?

    Disulfiram-like reaction. Metronidazole inhibits aldehyde dehydrogenase, causing accumulation of acetaldehyde from alcohol metabolism.

20. What is the key interaction between warfarin and rifampin?

    Decreased INR (reduced warfarin effect). Rifampin induces CYP2C9 and CYP3A4 enzymes, accelerating warfarin metabolism and diminishing its efficacy.

21. What is the key interaction risk when digoxin is used with loop or thiazide diuretics?

    Hypokalemia increases digoxin toxicity risk. These diuretics cause potassium loss, which sensitizes the heart to digoxin's effects on sodium-potassium ATPase.

22. What is the major interaction between clopidogrel and omeprazole (or esomeprazole)?

    Reduced clopidogrel activation/effect. These PPIs inhibit CYP2C19, which is necessary for converting clopidogrel to its active metabolite.

23. What is the key interaction between oral tetracyclines and calcium, iron, magnesium, or antacids?

    Reduced absorption (chelation). These cations form insoluble complexes with tetracyclines in the GI tract, impairing their bioavailability.

24. What serious electrolyte interaction can occur with spironolactone plus potassium chloride?

    Hyperkalemia. Spironolactone inhibits aldosterone, reducing potassium excretion, while potassium chloride directly supplements it.

25. What interaction occurs when alcohol is combined with opioids or benzodiazepines?

    Additive CNS/respiratory depression. Alcohol potentiates GABA-mediated inhibition, compounding the sedative effects of these CNS depressants.

Study these flashcards