A 52-year-old man with newly diagnosed hypertension (BP 168/104 mmHg) and hypokalemia (K⁺ 3.2 mEq/L) presents to the clinic. Serum sodium is 148 mEq/L. Plasma renin activity is suppressed (0.3 ng/mL/hr; normal 0.5–1.6). Aldosterone level is elevated at 28 ng/dL (normal <15). The patient denies use of diuretics or licorice. What is the most appropriate next step in management?