What is the appropriate management for a patient with hypertension and diabetes mellitus, taking lisinopril (angiotensin-converting enzyme inhibitor) and metformin (biguanide), with impaired renal function (eGFR 28) and elevated creatinine?

Management of a Patient with Hypertension, Diabetes, and Impaired Renal Function

Recommendation

Based on the patient's severely impaired renal function (eGFR 28 mL/min/1.73m²), both metformin and lisinopril should be discontinued. The correct answer is D. Discontinue lisinopril. 1, 2

Rationale for Discontinuing Lisinopril

1. Renal Function Concerns:

   • The patient has an eGFR of 28 mL/min/1.73m², which indicates Stage 4 chronic kidney disease
   • Lisinopril FDA labeling states that for patients with creatinine clearance ≥10 mL/min and ≤30 mL/min, the dose should be reduced to half the usual recommended dose 2
   • However, in this case, the patient is already on a maximum dose of lisinopril (40 mg daily), which is excessive for this level of renal function
   • The rising creatinine (compared to a year ago) suggests that the ACE inhibitor may be contributing to worsening renal function

2. Risk of Hyperkalemia and Further Renal Deterioration:

   • ACE inhibitors like lisinopril can cause hyperkalemia, especially in patients with renal insufficiency 2
   • The patient already has proteinuria (1+ protein in urine), indicating kidney damage
   • Continuing lisinopril at this high dose with declining renal function poses significant risks for further kidney deterioration

Rationale for Discontinuing Metformin

1. Contraindication in Severe Renal Impairment:

   • According to KDIGO 2022 guidelines, metformin is contraindicated in patients with eGFR <30 mL/min/1.73m² 1
   • The patient's eGFR of 28 mL/min/1.73m² falls below this threshold
   • The Canadian Society of Nephrology also recommends against metformin use in patients with GFR <30 mL/min/1.73m² 1

2. Risk of Lactic Acidosis:

   • While the absolute risk of lactic acidosis with metformin is low, it increases significantly in patients with severe renal impairment 1, 3
   • The combination of metformin and ACE inhibitors in patients with acute kidney injury can be particularly dangerous 4

Alternative Management Strategy

1. Blood Pressure Management:

   • Replace lisinopril with a non-RAAS blocking antihypertensive agent
   • Consider calcium channel blockers or thiazide-like diuretics if blood pressure control is needed
   • Monitor blood pressure closely after discontinuing lisinopril

2. Diabetes Management:

   • Replace metformin with an alternative hypoglycemic agent appropriate for CKD
   • According to KDIGO 2022 guidelines, preferred alternatives in advanced CKD include 1:
     • GLP-1 receptor agonists (preferred option)
     • DPP-4 inhibitors (dose adjustment required)
     • Insulin (may require dose adjustment)

3. Monitoring and Follow-up:

   • Check renal function and electrolytes within 1-2 weeks after medication changes
   • Monitor blood glucose levels more frequently during transition to new diabetes medication
   • Reassess proteinuria and consider nephrology referral if not already under specialist care

Important Considerations

• Hemoglobin A1c Target: The patient's current A1c of 6.5% is actually appropriate for their age and comorbidities. Less stringent targets (7-8%) may be reasonable in elderly patients with CKD
• Avoid Hypoglycemia: Elderly patients with renal impairment are at increased risk for hypoglycemia, especially when transitioning from metformin to other agents 5
• Patient Education: Instruct the patient about "sick day rules" - temporarily stopping certain medications during acute illness, especially those that may affect kidney function

By discontinuing both lisinopril and metformin and replacing them with more appropriate alternatives, we can reduce the risk of further renal deterioration, avoid potentially dangerous adverse effects, and maintain adequate control of both hypertension and diabetes.