Pharmacotherapy Newsletter

Volume 1, Issue 5, 02/16/2009

Question

How do ACE inhibitors (e.g., fosinopril, lisinopril, ramipril) cause hyperkalemia and who is really at risk?

Answer

Angiotensin converting enzyme (ACE) inhibitors are a well established class of medications that are used in the treatment of many conditions including, hypertension, congestive heart failure, and renal protection in patients with diabetes, to name a few.  Regardless of the indication, the risk of increasing serum potassium (K⁺) levels (i.e., hyperkalemia as defined by a serum K⁺ > 5.0 mEq/L) is a well known side effect.  In fact, ACE inhibitor induced hyperkalemia has been associated with 10 to 38% of hospital admissions, 10% of which develop it within 1 year of initiation.^1-3  So, how do ACE inhibitors increase potassium levels?