Abstract
Introduction: ACE inhibitors are renoprotective beyond their antihypertensive effects but can provoke or exacerbate hyperkalemia in advanced renal failure or diabetes mellitus (DM). It has been proposed that Angiotensin II antagonists (ARB) may produce less hyperkalemia, but the effects of ARB versus ACE inhibitors on dynamic renal potassium (K) excretion in response to an acute oral K challenge have not been tested quantitatively. Methods: Randomized crossover study of candesartan (C) versus lisinopril (L) titrated to blood pressure control. Study subjects: 23 patients with Type II DM, JNC VI Stage 1 hypertension, and mean (SD) serum creatinine 0.96 mg/dl (.18). In response to challenge with an acute oral K load (0.75 mEq/kg), K and creatinine (Cr) concentrations of serial urine and blood samples were determined to quantitate sequential changes in fractional excretion of potassium (FEK), rate of urinary potassium excretion (UkV), peak urinary potassium excretion (Peak UkV), and changes from baseline in FEK, UkV, and serum K. Results: [Mean (SEM)] Hourly FEK, UkV, Peak UkV, and serum K were similar for C and L although FEK at hour 2 for C tended to exceed that for L [.34(.04) vs. .26(.03)] and approached significance (p=.10). Similarly, UkV at hour 2 was 177(26) for C and 121(21) for L and approached significance (p=.10). Peak UkV and serum K did not differ between C and L. Conclusion: Our study demonstrates that C and L did not produce statistically significant differences in dynamic renal K handling in our subgroup of mildly hypertensive patients with type II diabetes mellitus and preserved renal function. Whether C and L produce significant differences in renal K handling in patients with renal impairment remains to be investigated. (See Table) FEK Baseline Hour 1 Hour 2 Hour 3 Hour 4 Hour 5 Candesartan .14 (.01) .17 (.03) .34 (.04) .29 (.02) .26 (.01) .22 (.02) Lisinopril .14 (.01) .18 (02) .26 (.03) .27 (.02) .23 (.01) .19 (.01) p-value .70 .50 .10 .37 .23 .18 UkV Baseline Hour 1 Hour 2 Hour 3 Hour 4 Hour 5 Candesartan 68 (8) 113 (17) 177 (26) 144 (15) 136 (15) 100 (10) Lisinopril 65 (7) 108 (14) 121 (21) 152 (25) 132 (17) 91(10.2) p-value .69 .92 .10 .79 .85 .53