A 68-year-old woman with a 10-year history of hypertension is found to have an eGFR of 32 mL/min/1.73 m² on routine screening. Serum creatinine is 2.1 mg/dL. She is currently on amlodipine 5 mg daily. Urinalysis is normal (no proteinuria). Blood pressure is 142/88 mmHg. She is asymptomatic with no signs of uremia. What is the most appropriate next step in management?