CPJE Drug Interactions and Therapeutics Flashcards

A patient on warfarin is prescribed ciprofloxacin. Which monitoring parameter should the pharmacist prioritize?

Answer: INR/PT levels

Ciprofloxacin inhibits warfarin metabolism, increasing anticoagulant effect and bleeding risk, so INR must be monitored closely.

Which drug combination is contraindicated due to the risk of serotonin syndrome?

Answer: Sertraline and linezolid

Linezolid is an MAO inhibitor; combining it with SSRIs like sertraline can precipitate life-threatening serotonin syndrome.

A patient taking simvastatin is started on clarithromycin. What is the primary concern?

Answer: Increased risk of myopathy/rhabdomyolysis

Clarithromycin inhibits CYP3A4, dramatically increasing simvastatin levels and the risk of myopathy or rhabdomyolysis.

Which interaction requires separating doses by at least 2 hours to prevent reduced drug absorption?

Answer: Levothyroxine and calcium carbonate

Calcium carbonate chelates levothyroxine in the GI tract, significantly reducing its absorption if taken simultaneously.

A patient on lithium is prescribed ibuprofen for pain. What adverse outcome is most likely?

Answer: Lithium toxicity due to elevated serum levels

NSAIDs reduce renal prostaglandin synthesis, decreasing lithium clearance and raising serum lithium to toxic levels.

Which mechanism explains the interaction between digoxin and amiodarone?

Answer: Amiodarone inhibits P-glycoprotein, increasing digoxin levels

Amiodarone inhibits P-gp-mediated renal and intestinal elimination of digoxin, increasing its plasma concentration.