Drug–Drug, Drug–Food, Drug–Disease - NAPLEX
- What is the interaction between clopidogrel and omeprazole?
- CYP2C19 inhibition reduces clopidogrel activation. Omeprazole inhibits CYP2C19, impairing conversion of clopidogrel to its active metabolite and reducing antiplatelet efficacy.
- What is the interaction between rifampin and many CYP substrates (e.g., apixaban)?
- Strong induction lowers drug levels; reduced efficacy. Rifampin potently induces multiple CYP enzymes, decreasing substrate concentrations and compromising therapeutic outcomes.
- Identify the disease state in which NSAIDs commonly worsen renal function and fluid status.
- Chronic kidney disease. NSAIDs inhibit prostaglandins that maintain renal perfusion, leading to acute kidney injury and fluid retention in CKD patients.
- What is the key drug–food interaction for MAO inhibitors with tyramine-rich foods?
- Hypertensive crisis risk. Tyramine displaces norepinephrine in the presence of MAO inhibition, causing acute hypertension and potential cardiovascular emergencies.
- Which anticonvulsant decreases oral contraceptive effectiveness via enzyme induction?
- Carbamazepine. Carbamazepine induces CYP3A4, accelerating estrogen metabolism and diminishing contraceptive reliability.
- What is the primary interaction mechanism between warfarin and amiodarone?
- CYP2C9 inhibition increases warfarin effect; INR rises. Amiodarone inhibits CYP2C9, reducing warfarin metabolism and potentiating its anticoagulant effects, which elevates INR levels.
- Identify the dangerous interaction between nitrates and PDE-5 inhibitors (e.g., sildenafil).
- Severe hypotension from additive vasodilation. Nitrates and PDE-5 inhibitors both promote vasodilation, leading to profound hypotension when combined.
- Which disease state is a contraindication to isotretinoin due to teratogenicity concerns?
- Pregnancy. Isotretinoin is a potent teratogen, causing severe fetal malformations, thus contraindicated during pregnancy.
- Which cardiac condition is a contraindication to nondihydropyridine CCBs (verapamil/diltiazem)?
- Heart failure with reduced ejection fraction (HFrEF). Nondihydropyridine CCBs depress myocardial contractility, worsening systolic dysfunction in HFrEF patients.
- Which antibiotic class is contraindicated with tizanidine due to CYP1A2 inhibition?
- Fluoroquinolones (especially ciprofloxacin). Fluoroquinolones inhibit CYP1A2, increasing tizanidine levels and risking severe hypotension or bradycardia.
- What is the interaction between ACE inhibitors and potassium-sparing diuretics?
- Hyperkalemia risk increases. Both classes promote potassium retention, leading to potentially life-threatening hyperkalemia.
- Which disease state makes nonselective beta-blockers risky due to bronchospasm?
- Asthma. Nonselective beta-blockers antagonize beta-2 receptors in airways, exacerbating bronchoconstriction in asthmatic patients.
- Which opioid partial agonist can precipitate withdrawal if given with full opioid agonists?
- Buprenorphine. Buprenorphine's high mu-receptor affinity displaces full agonists, inducing acute withdrawal symptoms in dependent individuals.
- What is the interaction between lithium and thiazide diuretics?
- Lithium levels increase; toxicity risk increases. Thiazides reduce lithium renal clearance, elevating serum levels and increasing toxicity risks like neurotoxicity.
- What is the drug–food interaction between metronidazole and alcohol?
- Disulfiram-like reaction risk. Metronidazole inhibits aldehyde dehydrogenase, causing acetaldehyde buildup and symptoms like flushing and nausea upon alcohol ingestion.
- Which antiarrhythmic is contraindicated with dofetilide due to QT prolongation risk?
- Verapamil. Verapamil increases dofetilide exposure via P-glycoprotein inhibition, amplifying QT prolongation and torsades de pointes risk.
- What is the drug–food interaction between tetracyclines and dairy products?
- Chelation reduces absorption. Calcium in dairy forms insoluble complexes with tetracyclines, decreasing antibiotic bioavailability and therapeutic effectiveness.
- Identify the interaction between trimethoprim-sulfamethoxazole and warfarin.
- INR increases; bleeding risk increases. Trimethoprim-sulfamethoxazole inhibits CYP2C9 and vitamin K-producing bacteria, potentiating warfarin's anticoagulant effects.
- What is the interaction between linezolid and SSRIs/SNRIs?
- Serotonin syndrome risk (MAOI activity). Linezolid's MAOI properties combined with serotonergic agents can cause excessive serotonin accumulation, leading to syndrome manifestations.
- What is the key drug–drug interaction between simvastatin and clarithromycin?
- CYP3A4 inhibition increases statin; rhabdomyolysis risk. Clarithromycin inhibits CYP3A4, elevating simvastatin levels and heightening the risk of muscle breakdown and kidney damage.
- Which beverage increases simvastatin/atorvastatin levels by inhibiting intestinal CYP3A4?
- Grapefruit juice. Grapefruit juice inhibits intestinal CYP3A4, reducing first-pass metabolism and elevating statin concentrations with myopathy risk.
- What is the key drug–food interaction between warfarin and vitamin K–rich foods?
- High vitamin K intake decreases warfarin effect (lower INR). Vitamin K antagonizes warfarin's inhibition of clotting factor synthesis, reducing anticoagulant efficacy and INR values.
- Identify the drug–food interaction for levothyroxine with calcium or iron products.
- Reduced absorption; separate administration. Calcium and iron bind levothyroxine, impairing gastrointestinal absorption and necessitating timed separation for optimal efficacy.
- What disease state makes metformin inappropriate due to increased lactic acidosis risk?
- Severe renal impairment. Severe renal impairment reduces metformin clearance, increasing lactate accumulation and lactic acidosis risk.
- What is the recommended warfarin action when starting amiodarone?
- Reduce warfarin dose and monitor INR closely. Amiodarone's inhibition of warfarin metabolism necessitates dose reduction and frequent INR monitoring to prevent bleeding complications.