North American Pharmacist Licensure Examination (NAPLEX) Drug Safety: Interactions, Adverse Effects, and Toxicology Syllabus

Drug Safety: Interactions, Adverse Effects, and Toxicology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Drug Safety: Interactions, Adverse Effects, and Toxicology in North American Pharmacist Licensure Examination (NAPLEX), not a summary of it.

1. 1

   Drug Interactions

   5 topics

   • CYP450 inhibitors, inducers, and substrates
   • P-glycoprotein and transporter-mediated interactions
   • Pharmacodynamic interactions and additive toxicity
   • Drug-food and drug-supplement interactions
   • QT-prolonging combinations
2. 2

   Adverse Drug Reactions and Monitoring

   5 topics

   • Type A vs Type B reactions
   • Black box warnings and REMS programs
   • Hypersensitivity and cross-reactivity
   • Organ-specific toxicities (hepato-, nephro-, cardiotoxicity)
   • Adverse event reporting (MedWatch)
3. 3

   Toxicology and Antidotes

   5 topics

   • Acetaminophen and salicylate overdose
   • Opioid and benzodiazepine reversal
   • Anticoagulant reversal agents
   • Common antidote-toxin pairs
     • Digoxin immune fab, fomepizole, naloxone
     • Cyanide and organophosphate antidotes
   • Decontamination and supportive measures
4. 4

   Special Populations and High-Risk Medications

   4 topics

   • Pregnancy and lactation safety
   • Pediatric dosing considerations
   • Geriatric pharmacotherapy and Beers Criteria
   • High-alert medication safety practices

Drug Safety: Interactions, Adverse Effects, and Toxicology flashcards for North American Pharmacist Licensure Examination (NAPLEX)

18 of 50 cards from the Drug Safety: Interactions, Adverse Effects, and Toxicology deck — real questions with worked answers.

1. What is the difference between a CYP450 inhibitor and inducer in terms of effect on substrate drug levels?

   An inhibitor decreases substrate metabolism, raising substrate concentrations and toxicity risk (rapid onset, hours to days). An inducer increases enzyme synthesis, lowering substrate concentrations and efficacy (delayed onset, ~1-2 weeks; reversal also delayed).

2. Name the major strong CYP3A4 inhibitors a NAPLEX student should memorize.

   Azole antifungals (ketoconazole, itraconazole, voriconazole), clarithromycin, erythromycin, ritonavir/cobicistat, and grapefruit juice (intestinal CYP3A4). Mnemonic aid: protease inhibitors and -azoles are potent 3A4 inhibitors.

3. Name the classic strong CYP enzyme inducers.

   Rifampin, carbamazepine, phenytoin, phenobarbital, St. John's wort, and (chronic) ethanol/smoking for specific isoenzymes. These lower levels of many substrates including warfarin, oral contraceptives, and many statins.

4. Which CYP2D6 inhibitors can blunt the analgesic effect of codeine and tramadol?

   Strong 2D6 inhibitors (fluoxetine, paroxetine, bupropion, quinidine) block conversion of codeine to morphine and tramadol to its active metabolite, reducing analgesia. CYP2D6 is the relevant prodrug-activating enzyme.

5. What is the clinical concern with CYP2C19 and clopidogrel?

   Clopidogrel is a prodrug activated by CYP2C19. Poor metabolizers (genetic) or 2C19 inhibitors (omeprazole, esomeprazole) reduce active metabolite formation and antiplatelet effect, increasing thrombotic risk.

6. How does P-glycoprotein (P-gp) inhibition affect substrate drugs like digoxin and dabigatran?

   P-gp is an efflux transporter. Inhibitors (amiodarone, verapamil, clarithromycin, quinidine, cyclosporine) reduce efflux, increasing absorption and serum levels of P-gp substrates (digoxin, dabigatran, edoxaban), raising toxicity risk.

7. What transporter mediates the statin-related interaction with cyclosporine and gemfibrozil, raising myopathy risk?

   OATP1B1 (organic anion-transporting polypeptide), which mediates hepatic uptake of statins. Inhibition by cyclosporine or gemfibrozil raises statin plasma levels and increases rhabdomyolysis risk.

8. Define a pharmacodynamic drug interaction and give an example of additive toxicity.

   A pharmacodynamic interaction occurs when drugs have additive, synergistic, or antagonistic effects at the same or related receptors/systems without changing plasma levels. Example: opioid + benzodiazepine causing additive CNS/respiratory depression.

9. Why is the combination of an ACE inhibitor, a potassium-sparing diuretic, and a potassium supplement dangerous?

   Additive (pharmacodynamic) hyperkalemia. Each raises serum potassium, and combined use can cause life-threatening $K^{+}$ elevation and cardiac arrhythmias.

10. What is the mechanism of the grapefruit juice-drug interaction?

    Grapefruit juice irreversibly inhibits intestinal CYP3A4 (and some P-gp), increasing oral bioavailability of substrates such as felodipine, simvastatin, lovastatin, and certain calcium channel blockers, raising toxicity risk.

11. Name a key drug-supplement interaction involving St. John's wort.

    St. John's wort is a strong CYP3A4 and P-gp inducer, reducing levels of oral contraceptives, cyclosporine, warfarin, digoxin, and certain antiretrovirals. It also raises serotonin syndrome risk with serotonergic drugs.

12. Which mineral-containing foods/supplements chelate fluoroquinolones and tetracyclines, reducing absorption?

    Polyvalent cations: calcium, magnesium, aluminum (antacids), iron, and zinc. Separate dosing (e.g., quinolone 2 h before or 6 h after) to avoid chelation and reduced absorption.

13. What dietary interaction is critical for patients taking MAO inhibitors?

    Tyramine-rich foods (aged cheeses, cured meats, fermented products, draft beer) can precipitate a hypertensive crisis because MAOIs block tyramine breakdown, causing massive catecholamine release.

14. List three common drug classes that prolong the QT interval.

    Class IA/III antiarrhythmics (quinidine, sotalol, amiodarone, dofetilide), macrolides and fluoroquinolones, antipsychotics (haloperidol, ziprasidone), methadone, and ondansetron. Combining them increases torsades de pointes risk.

15. Which electrolyte abnormalities potentiate QT prolongation and torsades risk?

    Hypokalemia, hypomagnesemia, and hypocalcemia. Correcting these (especially giving IV magnesium) is part of preventing and treating drug-induced torsades de pointes.

16. Distinguish Type A from Type B adverse drug reactions.

    Type A (Augmented): dose-dependent, predictable, related to the drug's pharmacology, common, low mortality (e.g., warfarin bleeding). Type B (Bizarre): dose-independent, unpredictable, often immunologic/idiosyncratic, rare, higher mortality (e.g., anaphylaxis, SJS).

17. What is a Black Box Warning?

    The FDA's strongest warning, placed in a bordered box at the top of prescribing information, highlighting serious or life-threatening risks (e.g., NSAIDs and CV/GI risk, fluoroquinolones and tendon rupture, SSRIs and suicidality in young patients).

18. What is a REMS program and when is it required?

    Risk Evaluation and Mitigation Strategy: an FDA-required safety program ensuring a drug's benefits outweigh its risks. May include a Medication Guide, communication plan, and Elements to Assure Safe Use (ETASU) such as prescriber/pharmacy certification or patient enrollment (e.g., isotretinoin/iPLEDGE, clozapine, thalidomide).

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