A 72-year-old man with a history of hypertension, type 2 diabetes, and chronic kidney disease (CKD) presents to his general practitioner for a routine check-up. His current medications include metformin, insulin, amlodipine, and aspirin. His blood pressure today is 150/90 mmHg. Laboratory results show a serum creatinine of 2.5 mg/dL (221 micromol/L) and a potassium level of 5.4 mEq/L. The GP decides to add an ACE inhibitor to his treatment regimen to help manage his blood pressure and provide renal protection. One week later, the patient returns complaining of fatigue and muscle weakness. Repeat laboratory tests reveal a serum creatinine of 3.1 mg/dL (274 micromol/L) and a potassium level of 6.2 mEq/L. Which of the following is the most appropriate next step in managing this patient?