CETP Drug Interactions 2

Question 1

Oral fluoroquinolone antibiotics should be taken at least 2 hours before or 6 hours after antacids containing aluminum or magnesium because of which interaction mechanism?

Accepted Answer

Chelation forming insoluble complexes that reduce fluoroquinolone absorption

Answer

Polyvalent cations (Al3+, Mg2+, Ca2+, Fe2+) chelate fluoroquinolones in the GI tract, forming insoluble complexes that are poorly absorbed, significantly reducing antibiotic bioavailability.

Question 2

A patient stabilized on lithium therapy is prescribed ibuprofen for arthritis pain. What pharmacokinetic change should the pharmacist anticipate?

Accepted Answer

Increased lithium levels due to reduced renal clearance

Answer

NSAIDs inhibit renal prostaglandin synthesis, reducing renal blood flow and decreasing lithium clearance, which raises lithium plasma levels and increases toxicity risk.

Question 3

Co-administration of simvastatin with which medication carries the highest risk of inducing rhabdomyolysis?

Accepted Answer

Gemfibrozil

Answer

Gemfibrozil inhibits OATP1B1 and CYP2C8, significantly reducing simvastatin clearance and increasing muscle exposure, leading to a markedly elevated risk of myopathy and rhabdomyolysis.

Question 4

Digoxin toxicity risk increases significantly when which electrolyte imbalance is caused by a concomitant medication?

Accepted Answer

Hypokalemia

Answer

Hypokalemia increases the binding of digoxin to Na+/K+-ATPase and enhances its toxic effects; loop and thiazide diuretics can precipitate this interaction by causing potassium wasting.

Question 5

St. John's Wort (Hypericum perforatum) reduces plasma levels of many medications including cyclosporine and HIV protease inhibitors through which primary mechanism?

Accepted Answer

Induction of CYP3A4 and P-glycoprotein

Answer

St. John's Wort is a potent inducer of CYP3A4 and P-glycoprotein, accelerating the metabolism and efflux of many drugs, leading to subtherapeutic concentrations.

CETP - Canadian Entry To Practice Practice Test

CETP - Canadian Entry To Practice Practice Test

CETP Drug Interactions 2