How to manage a 64-year-old female with impaired renal function (Glomerular Filtration Rate (GFR) of 51) after starting triamterene (a potassium-sparing diuretic)-hydrochlorothiazide (HCTZ) (a thiazide diuretic)?

Management of Impaired Renal Function After Starting Triamterene-HCTZ

Triamterene-HCTZ should be discontinued immediately in this 64-year-old female with new GFR of 51 ml/min. 1

Assessment of Medication-Induced Renal Impairment

• Current situation:

  • 64-year-old female
  • New GFR of 51 ml/min (Stage 3a CKD)
  • Temporal relationship with triamterene-HCTZ initiation

• Risk factors present:

  • Age >60 years 2
  • Female gender (may have higher risk of adverse effects from diuretics) 3
  • Moderate renal impairment

Mechanism of Renal Impairment

1. Triamterene toxicity:

   • Can cause direct tubular obstruction with crystal deposition 4
   • FDA label specifically warns about renal impairment with triamterene 1

2. Potassium-sparing effects:

   • Triamterene is contraindicated in patients with pre-existing elevated serum potassium or impaired renal function 1
   • Hyperkalemia risk increases with declining GFR

Management Algorithm

Step 1: Immediate Actions

• Discontinue triamterene-HCTZ immediately 1
• Check serum electrolytes (especially potassium)
• Obtain ECG to assess for hyperkalemia-related changes
• Assess volume status

Step 2: Alternative Antihypertensive Selection

Based on GFR of 51 ml/min, select from:

1. First-line options:

   • ACE inhibitor (e.g., lisinopril 10 mg daily) 5
   • ARB (e.g., losartan 50 mg daily) 5
   • Calcium channel blocker (e.g., amlodipine 5 mg daily) 3

2. If additional therapy needed:

   • Loop diuretic (e.g., furosemide) if volume overload is present 3
   • Avoid thiazide diuretics with GFR <30 ml/min 3
   • Avoid potassium-sparing diuretics with GFR <45 ml/min 3

Step 3: Monitoring

• Recheck renal function in 1-2 weeks after medication change
• Monitor serum potassium closely, especially if starting ACE inhibitor or ARB
• Adjust medication dosage based on BP response and renal function

Special Considerations

• Hyperkalemia management: If present, treat according to severity (calcium gluconate for cardiac stabilization, sodium bicarbonate, glucose/insulin, or sodium polystyrene sulfonate) 1

• Volume status: Ensure adequate hydration, as volume depletion can worsen renal function 2

• Drug combinations: Avoid nephrotoxic drug combinations (e.g., NSAIDs with diuretics) 6

• Medication dosing: Adjust medication doses based on current GFR 3

Prognosis

With prompt discontinuation of the offending agent, renal function may improve, though complete recovery is not guaranteed. Some cases of triamterene-induced renal failure have been reported to be irreversible 4. Close monitoring of renal function over the following weeks is essential to determine if the decline is reversible.