MTM Renal Dosing & Adjustments 4 — Questions and Answers
Question 1: A patient with CrCl of 15 mL/min develops a urinary tract infection. Which antibiotic should be AVOIDED due to inadequate urinary concentrations in severe renal failure?
- Trimethoprim-sulfamethoxazole
- Nitrofurantoin (Correct answer)
- Fosfomycin
- Amoxicillin-clavulanate
Correct answer: Nitrofurantoin
Nitrofurantoin is ineffective in severe renal failure because it cannot achieve adequate urinary concentrations and may accumulate to cause toxicity.
Question 2: Which aminoglycoside monitoring strategy is most appropriate in a patient with fluctuating renal function?
- Fixed interval dosing with trough monitoring
- Extended-interval dosing (once-daily)
- Traditional multiple daily dosing with peak/trough levels (Correct answer)
- Continuous infusion without monitoring
Correct answer: Traditional multiple daily dosing with peak/trough levels
Patients with unstable renal function require traditional dosing with frequent peak and trough monitoring to safely individualize therapy.
Question 3: A pharmacist reviews a patient's regimen and notes they are on apixaban 5 mg BID with a CrCl of 25 mL/min. What action is most appropriate?
- No change needed; apixaban is not renally cleared
- Reduce to 2.5 mg BID based on renal criteria
- Discontinue apixaban and switch to warfarin (Correct answer)
- Increase monitoring frequency only
Correct answer: Discontinue apixaban and switch to warfarin
While apixaban has limited renal elimination, patients with severe CKD (CrCl < 25 mL/min) were excluded from ARISTOTLE trial; switching to warfarin is often recommended.
Question 4: Which electrolyte abnormality is most commonly associated with progressive CKD and affects drug therapy choices?
- Hyponatremia
- Hyperkalemia (Correct answer)
- Hypocalcemia
- Hypomagnesemia
Correct answer: Hyperkalemia
Hyperkalemia is common in CKD and restricts use of drugs that increase potassium, such as ACE inhibitors, ARBs, and potassium-sparing diuretics.
Question 5: A patient on hemodialysis three times weekly needs pain management. Which opioid is considered SAFEST in this population?
- Codeine
- Morphine
- Hydromorphone
- Fentanyl (Correct answer)
Correct answer: Fentanyl
Fentanyl is preferred in dialysis patients because it has inactive metabolites and is not significantly renally eliminated.
Question 6: The prescribing information for a drug states 'reduce dose by 50% when CrCl is 30-60 mL/min.' A patient's estimated CrCl is 45 mL/min. What is this adjustment based on?
- Pharmacodynamic studies
- Phase III clinical trials only
- Pharmacokinetic studies measuring drug exposure at different renal function levels (Correct answer)
- Post-marketing surveillance data
Correct answer: Pharmacokinetic studies measuring drug exposure at different renal function levels
Renal dose adjustment recommendations derive from pharmacokinetic studies that measure AUC and clearance at varying levels of kidney function.
Question 7: Which proton pump inhibitor requires the LEAST concern for dose adjustment in severe renal impairment?
- Omeprazole
- Lansoprazole
- Pantoprazole
- All PPIs require equal adjustment in renal failure (Correct answer)
Correct answer: All PPIs require equal adjustment in renal failure
PPIs are primarily hepatically metabolized with minimal renal elimination, so none require dose adjustment for renal impairment.
MTM Renal Dosing & Adjustments 4
A patient with CrCl of 15 mL/min develops a urinary tract infection.
Which antibiotic should be AVOIDED due to inadequate urinary concentrations in severe renal failure?