A 58-year-old man with hypertension and chronic kidney disease (eGFR 35 mL/min/1.73m²) is prescribed a diuretic for fluid overload. Which is the most common adverse effect of loop diuretics in this patient?

Explanation

## Most Common Adverse Effect of Loop Diuretics **Key Point:** Hypokalemia is the most frequent and clinically significant adverse effect of loop diuretics, occurring in up to 20–30% of patients on chronic therapy. ### Mechanism of Hypokalemia 1. Loop diuretics inhibit the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb 2. Increased urinary K⁺ excretion due to: - Increased distal delivery of Na⁺ (enhanced distal secretion of K⁺) - Activation of the renin-angiotensin-aldosterone system (RAAS) → aldosterone-mediated K⁺ wasting 3. Volume depletion triggers compensatory RAAS activation ### Clinical Significance in This Patient | Feature | Relevance | |---------|----------| | **CKD (eGFR 35)** | Reduced renal reserve; K⁺ wasting more pronounced | | **Hypokalemia risk** | Arrhythmias, muscle weakness, worsening renal function | | **Frequency** | Most common electrolyte abnormality with loop diuretics | **High-Yield:** Hypokalemia is the leading cause of discontinuation or dose reduction of loop diuretics in clinical practice. ### Why Other Effects Are Less Common - **Hyperuricemia** — occurs but less frequent than hypokalemia; mechanism is volume depletion → ↓ uric acid clearance - **Ototoxicity** — rare, seen only with high-dose IV furosemide (especially in renal failure); not a common outpatient problem - **Hyperglycemia** — occurs but less common than hypokalemia; mechanism involves hypokalemia-induced impaired insulin secretion **Clinical Pearl:** In CKD patients, concurrent ACE inhibitor or ARB use can partially mitigate loop diuretic-induced hypokalemia by blocking aldosterone. **Mnemonic: KALE** — **K**⁺ loss, **A**lkalosis, **L**oop diuretics, **E**lectrolyte imbalance.