ACE Inhibitor Cough in CKD with Potassium 5.4
A 68-year-old woman with hypertension and stage 3b chronic kidney disease (eGFR 38 mL/min/1.73 m²) presents with an 8-week dry, tickling cough. She takes lisinopril 20 mg daily, hydrochlorothiazide 25 mg daily, potassium chloride 20 mEq daily, and ibuprofen 400 mg two to three times daily for knee osteoarthritis. She has no fever, wheeze, or nasal symptoms. BP is 138/82 mmHg; HR 76 bpm. Labs from last week: creatinine 1.6 mg/dL, potassium 5.4 mmol/L, bicarbonate 20 mmol/L, hemoglobin 11.2 g/dL. She reports mild fatigue but no palpitations or muscle weakness. She wants to know whether the cough is from her blood pressure medication and whether she can take an herbal cough syrup containing licorice. She is reluctant to stop ibuprofen because it helps her knees.
1. Which medication is the likely cause of the cough, and what other prescribing problem is present?
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The dry, tickling cough without fever, wheeze, or nasal symptoms is most consistent with an ACE inhibitor cough from lisinopril. ACE inhibitor cough is due to bradykinin accumulation and typically resolves within 1 to 4 weeks after stopping the drug. Other causes such as asthma, postnasal drip, GERD, and heart failure should still be considered if the cough does not resolve after the ACE inhibitor is stopped.
The more urgent problem is hyperkalemia in the setting of CKD. Potassium is 5.4 mmol/L, and she is taking potassium chloride plus an ACE inhibitor plus ibuprofen. NSAIDs reduce renal potassium excretion and can worsen CKD, and the potassium supplement is unnecessary at this level. Licorice is also inappropriate: it causes pseudohyperaldosteronism with hypertension and hypokalemia, but in this patient it adds unnecessary risk and can interact with blood pressure control. The immediate priorities are to stop the potassium chloride and ibuprofen, review dietary potassium, and assess for ECG changes.
2. How should you adjust therapy and monitor?
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I would stop potassium chloride and ibuprofen now. I would obtain an ECG to look for peaked T waves or widening of the QRS, and repeat potassium, creatinine, and bicarbonate within 48 to 72 hours. If potassium is above 5.5 mmol/L or there are ECG changes, she needs urgent evaluation. She should avoid salt substitutes and licorice-containing products.
For blood pressure and kidney protection, I would not simply stop lisinopril without a plan. If the cough is intolerable, switching to an ARB such as losartan is reasonable, but ARBs can also raise potassium, so monitoring is required. If potassium remains elevated, I would consider stopping the ARB/ACE inhibitor temporarily, adding a potassium binder if appropriate, and treating metabolic acidosis. For her knee pain, topical NSAID or acetaminophen may be safer than oral ibuprofen, with attention to kidney function. Follow-up should include repeat labs and blood pressure review.