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 Hypertension and Diabetes in a Patient with Impaired Renal Function

Based on the patient's eGFR of 28 mL/min/1.73m² and rising creatinine, the appropriate management is to discontinue both metformin and lisinopril (option D).

Assessment of Current Situation

The patient presents with:

• 78-year-old female with hypertension and diabetes
• Current medications: lisinopril 40 mg daily and metformin ER 1 gram daily
• Laboratory findings:
  • Glucose: 190 mg/dL
  • HbA1c: 6.5%
  • Creatinine: 1.8 mg/dL (increased from previous year)
  • eGFR: 28 mL/min/1.73m²
  • Proteinuria: 1+

Metformin Management

Metformin is contraindicated in this patient due to:

1. Severe renal impairment: KDIGO 2022 guidelines clearly state that metformin should not be used in patients with eGFR <30 mL/min/1.73m² 1. The patient's eGFR of 28 places her below this threshold.

2. Risk of lactic acidosis: Though rare, the risk of lactic acidosis increases significantly in patients with severely impaired renal function 1. The Canadian Society of Nephrology commentary notes that metformin is renally excreted and its clearance is proportional to GFR 1.

3. Rising creatinine: The patient's creatinine has increased compared to the previous year, indicating worsening kidney function, which further contraindicates metformin use.

Lisinopril Management

Lisinopril should also be discontinued for the following reasons:

1. Worsening renal function: ACE inhibitors like lisinopril can cause changes in renal function including acute renal failure, especially in patients with already compromised kidney function 2.

2. FDA labeling: According to the FDA label, in patients with creatinine clearance ≥10 mL/min and ≤30 mL/min, the dose of lisinopril should be reduced to half of the usual recommended dose 2. However, given the patient's worsening renal function, discontinuation is warranted.

3. Proteinuria with declining GFR: The combination of proteinuria and declining GFR suggests diabetic nephropathy, which is being potentially worsened by the high dose of lisinopril (40 mg).

Alternative Management Strategy

After discontinuing both medications:

1. For diabetes management:

   • Consider DPP-4 inhibitors or insulin therapy, which are safer in severe renal impairment 1
   • KDIGO 2022 guidelines recommend GLP-1 receptor agonists as preferred agents for patients with T2D and CKD who cannot use metformin 1

2. For hypertension management:

   • Consider calcium channel blockers or appropriate dose-adjusted diuretics
   • If an ACE inhibitor or ARB is still deemed necessary, it should be reintroduced at a much lower dose only after renal function stabilizes

3. Monitoring:

   • Close monitoring of renal function (every 1-3 months)
   • Regular assessment of electrolytes, particularly potassium
   • Continued monitoring of glycemic control

Pitfalls to Avoid

1. Continuing metformin despite severe renal impairment: This increases the risk of lactic acidosis, a rare but potentially fatal complication 3.

2. Simply reducing lisinopril dose: While dose reduction is an option for moderate renal impairment, the patient's declining renal function suggests that complete discontinuation is safer until kidney function stabilizes.

3. Focusing only on glycemic control: The HbA1c of 6.5% is actually appropriate for this elderly patient, and aggressive glycemic management could lead to hypoglycemia, which carries significant mortality risk in the elderly.

4. Ignoring the progression of kidney disease: The rising creatinine and proteinuria indicate progressive kidney disease that requires prompt intervention to prevent further deterioration.

By discontinuing both medications, the healthcare provider can reassess the patient's renal function, determine if it stabilizes or improves, and then develop an appropriate medication regimen that balances control of hypertension and diabetes while protecting kidney function.