MTM Renal Dosing & Adjustments 5 — Questions and Answers
Question 1: An MTM pharmacist identifies that a patient with CrCl of 20 mL/min is prescribed colchicine 0.6 mg BID for gout prophylaxis. What is the recommended approach?
- Continue current dose with monitoring
- Reduce to 0.3 mg once daily
- Contraindicated; discontinue colchicine entirely
- Switch to a maximum dose of 0.6 mg once daily with close monitoring (Correct answer)
Correct answer: Switch to a maximum dose of 0.6 mg once daily with close monitoring
Colchicine dose should be reduced to 0.3 mg once daily (or 0.6 mg every other day) in severe renal impairment to prevent neuromuscular toxicity.
Question 2: A patient with CKD stage 3b (CrCl 35 mL/min) is on lisinopril 10 mg daily. Serum potassium rises to 5.8 mEq/L. What is the BEST MTM recommendation?
- Continue lisinopril; hyperkalemia is expected and acceptable
- Reduce lisinopril dose and add a loop diuretic to manage potassium (Correct answer)
- Stop lisinopril immediately and start amlodipine
- Add a potassium supplement to prevent further rises
Correct answer: Reduce lisinopril dose and add a loop diuretic to manage potassium
Dose reduction of the ACE inhibitor combined with a potassium-wasting diuretic addresses both renal protection and hyperkalemia management.
Question 3: Which NSAID-related mechanism is most responsible for acute kidney injury in patients with pre-existing CKD?
- Direct tubular toxicity
- Inhibition of prostaglandin-mediated afferent arteriole dilation (Correct answer)
- Immune-mediated interstitial nephritis
- Increased uric acid crystallization
Correct answer: Inhibition of prostaglandin-mediated afferent arteriole dilation
NSAIDs block prostaglandins that dilate the afferent arteriole, reducing GFR critically in CKD patients who depend on this mechanism.
Question 4: A patient with ESRD on hemodialysis is prescribed pregabalin for neuropathic pain. The standard dose is 150 mg BID. What adjustment is needed?
- No adjustment needed
- Reduce to 25-75 mg once daily with supplemental dose after dialysis (Correct answer)
- 50% dose reduction to 75 mg BID
- Pregabalin is contraindicated in dialysis patients
Correct answer: Reduce to 25-75 mg once daily with supplemental dose after dialysis
Pregabalin is renally cleared and removed by hemodialysis; patients with ESRD require significant dose reduction and a supplemental post-dialysis dose.
Question 5: When evaluating a medication list for a CKD patient, which drug interaction specifically WORSENS renal function and requires immediate attention?
- Metformin + sitagliptin
- ACE inhibitor + NSAID (Correct answer)
- Amlodipine + diltiazem
- Atorvastatin + ezetimibe
Correct answer: ACE inhibitor + NSAID
ACE inhibitors reduce efferent arteriole tone while NSAIDs reduce afferent arteriole tone, together severely dropping GFR and worsening CKD.
Question 6: Which statement about trimethoprim (TMP) and serum creatinine is clinically important for MTM pharmacists?
- TMP causes true GFR reduction by damaging nephrons
- TMP blocks tubular creatinine secretion, raising serum creatinine without true GFR change (Correct answer)
- TMP increases creatinine production via muscle breakdown
- TMP has no effect on serum creatinine levels
Correct answer: TMP blocks tubular creatinine secretion, raising serum creatinine without true GFR change
Trimethoprim competitively inhibits tubular creatinine secretion, causing a rise in serum creatinine that does not reflect actual GFR decline.
Question 7: A pharmacist is performing MTM for a patient with CrCl of 40 mL/min taking rivaroxaban 20 mg daily for atrial fibrillation. What recommendation is appropriate?
- Continue current regimen; no adjustment needed at this CrCl
- Reduce to 15 mg daily with the evening meal (Correct answer)
- Switch to rivaroxaban 10 mg daily
- Discontinue rivaroxaban; it is contraindicated below CrCl 50 mL/min
Correct answer: Reduce to 15 mg daily with the evening meal
For non-valvular AF patients with CrCl 15–50 mL/min, rivaroxaban should be reduced to 15 mg once daily with the evening meal.
MTM Renal Dosing & Adjustments 5
An MTM pharmacist identifies that a patient with CrCl of 20 mL/min is prescribed colchicine 0.6 mg BID for gout prophylaxis.
What is the recommended approach?