Drug Prescribing and Monitoring — Dosage adjustment

A 78-year-old woman is seen 1 week after discharge from hospital, where she completed treatment for pneumonia with clarithromycin. She has hypertension, type 2 diabetes, and heart failure, and over the past 3 days she has had fatigue, weakness in her legs and then her arms, dizziness, poor oral intake, and a fall at home without head injury. Her medications are acetaminophen, atorvastatin, ramipril, amlodipine, mirtazapine, metformin, metoprolol, citalopram, and spironolactone; she has no known drug allergies. On examination she is alert and hemodynamically stable with dry mucous membranes, and ECG shows sinus bradycardia without heart block or peaked T waves. Potassium is 5.6 mmol/L (3.5-5.0), creatinine 155 µmol/L (45-90), eGFR 29 mL/min/1.73 m² (greater than 60; it was 52 six months ago), random glucose 6.2 mmol/L, HbA1c 8.5% (4.0-6.0), and creatine kinase is normal.