MTM Pharmacotherapy Review & Drug Interactions 3

Question 1

A patient with chronic kidney disease (eGFR 20 mL/min) is taking gabapentin. What dose adjustment is required?

Accepted Answer

Reduce dose and/or frequency; gabapentin is renally eliminated

Answer

Gabapentin is exclusively renally eliminated without hepatic metabolism, requiring significant dose reduction in renal impairment to prevent neurotoxicity.

Question 2

Which drug interaction mechanism explains the reduced effectiveness of oral contraceptives when rifampin is co-administered?

Accepted Answer

Rifampin induces CYP3A4, accelerating estrogen metabolism

Answer

Rifampin is a potent CYP3A4 inducer that significantly increases the metabolism of ethinyl estradiol and progestin components of oral contraceptives, reducing their plasma concentrations.

Question 3

In an MTM session, a patient on digoxin reports starting clarithromycin for a respiratory infection. What is the interaction mechanism?

Accepted Answer

Clarithromycin inhibits P-glycoprotein and CYP3A4, increasing digoxin levels

Answer

Clarithromycin inhibits P-glycoprotein (which normally effluxes digoxin from intestinal cells and renal tubules), leading to increased digoxin absorption and decreased renal elimination.

Question 4

A patient with heart failure has a serum potassium of 3.1 mEq/L and takes digoxin and furosemide. What is the primary concern?

Accepted Answer

Hypokalemia increases cardiac sensitivity to digoxin toxicity

Answer

Hypokalemia enhances digoxin binding to the Na+/K+-ATPase pump and increases myocardial sensitivity to digoxin, raising the risk of arrhythmias at normal or even subtherapeutic digoxin levels.

Question 5

Which antidiabetic agent class carries the highest risk of hypoglycemia when used as monotherapy?

Accepted Answer

Sulfonylureas

Answer

Sulfonylureas stimulate insulin secretion independently of blood glucose levels, making hypoglycemia a significant risk even without co-administration of other agents.

(MTM) Medication Therapy Management Board Certification Practice Test

(MTM) Medication Therapy Management Board Certification Practice Test

MTM Pharmacotherapy Review & Drug Interactions 3