What adjustments should be made to a 71-year-old male's medication regimen, including Hydrochlorothiazide (HCTZ) and Losartan, given his declining Glomerular Filtration Rate (GFR) and Impaired Renal Function?

Medication Adjustments for a 71-Year-Old Male with Declining Renal Function

For a 71-year-old male with declining renal function (BUN 32, creatinine 1.6, GFR 46 from prior 49) on hydrochlorothiazide (HCTZ) and losartan, the HCTZ should be discontinued and losartan dose should be maintained with close monitoring of renal function and electrolytes.

Assessment of Current Status

The patient presents with:

• Mild to moderate chronic kidney disease (CKD Stage 3a: GFR 46 ml/min/1.73m²)
• Slight decline in renal function from previous GFR of 49
• Current medications: HCTZ (thiazide diuretic) and losartan (ARB)

Recommended Medication Adjustments

1. Hydrochlorothiazide (HCTZ)

• Discontinue HCTZ as it has reduced efficacy in patients with GFR <45-50 ml/min/1.73m² 1
• Thiazide diuretics become less effective as GFR declines and may contribute to further deterioration of renal function 2
• Consider replacing with a loop diuretic if diuresis is still needed for volume management 1, 3

2. Losartan

• Maintain current losartan dose as no dose adjustment is necessary for patients with this level of renal impairment unless the patient is volume depleted 4
• Continue to monitor renal function closely, as an initial decline in GFR with ARB therapy is expected and may actually predict better long-term renal outcomes 5
• If creatinine increases >30% from baseline or hyperkalemia develops, consider dose reduction or discontinuation 3

Monitoring Recommendations

1. Renal Function:

   • Check serum creatinine, BUN, and eGFR within 1-2 weeks after medication changes 3
   • Monitor renal function more frequently (every 1-3 months) due to age and declining GFR 1

2. Electrolytes:

   • Monitor serum potassium closely, especially after discontinuing HCTZ (which can mask hyperkalemia caused by losartan) 1
   • Check serum sodium, as ARBs can cause hyponatremia, especially in elderly patients 1

3. Blood Pressure:

   • Target systolic blood pressure <120-130 mmHg using standardized office BP measurement 1, 3
   • More frequent BP monitoring after medication changes

Rationale for Recommendations

1. HCTZ discontinuation:

   • Thiazide diuretics have significantly reduced efficacy when GFR falls below 45-50 ml/min/1.73m² 2
   • HCTZ may contribute to further deterioration of renal function in patients with CKD 1
   • The risk of adverse effects (electrolyte disturbances, worsening renal function) outweighs benefits in this patient 1, 6

2. Maintaining losartan:

   • ARBs provide renoprotective effects in patients with CKD, especially those with proteinuria 7
   • Losartan specifically has been shown to be well-tolerated in patients with renal impairment 8
   • An initial decline in GFR with ARB therapy is expected and may predict better long-term renal outcomes 5
   • No dose adjustment is necessary for losartan in patients with renal impairment unless volume depleted 4

Common Pitfalls to Avoid

1. Abrupt discontinuation of both medications:

   • Could lead to rebound hypertension and worsening of renal function

2. Continuing HCTZ despite reduced GFR:

   • Reduced efficacy and increased risk of adverse effects

3. Ignoring the expected initial decline in GFR with ARB therapy:

   • A modest and stable increase in serum creatinine (up to 30%) is expected and should not prompt discontinuation 1, 5

4. Inadequate monitoring:

   • Elderly patients with CKD require more frequent monitoring of renal function and electrolytes 1, 3

5. Overlooking cardiovascular risk:

   • Patients with CKD Stage 3a have significantly increased cardiovascular risk compared to those with normal kidney function 3

By discontinuing HCTZ and maintaining losartan with appropriate monitoring, this approach balances blood pressure control with renoprotection while minimizing the risk of further renal function decline in this elderly patient with CKD.