Hyperkalemia: Drug Stacking Risk

Hyperkalemia drug stacking refers to the cumulative effect of multiple medications that independently increase serum potassium, creating dangerous additive or synergistic hyperkalemia risk. The RAAS pathway is the most common source of drug stacking: ACE inhibitors reduce angiotensin II → decreased aldosterone → decreased renal K+ excretion; ARBs block AT1 receptors → same downstream effect; potassium-sparing diuretics (spironolactone, eplerenone, amiloride, triamterene) directly reduce renal K+ excretion; NSAIDs reduce prostaglandin-mediated renin release → decreased aldosterone → decreased K+ excretion AND reduce renal blood flow. The 'triple whammy' combination (ACEi/ARB + diuretic + NSAID) causes acute kidney injury and hyperkalemia. High-risk combinations include: ACEi + spironolactone + NSAID; ACEi + ARB (dual RAAS blockade — NEVER recommended); ACEi/ARB + trimethoprim (TMP blocks ENaC like amiloride, causing K+ retention); ACEi/ARB + heparin (suppresses aldosterone synthesis); beta-blockers (impair cellular K+ uptake by blocking beta-2 mediated Na-K-ATPase); calcineurin inhibitors (cyclosporine, tacrolimus — reduce renal K+ excretion). Patient risk factors that amplify drug-stacking risk: CKD (already impaired K+ excretion), diabetes (type IV RTA/hypoaldosteronism), older age (decreased GFR, decreased aldosterone), heart failure (poor renal perfusion), dehydration (decreased...