Comparative Effects on Dynamic Renal Potassium Excretion of ACE Inhibition versus Angiotensin Receptor Blockade in Hypertensive Patients with Type II Diabetes Mellitus

Both ACE inhibitors (ACEI) and angiotensin receptor blockers (ARB) are renoprotective beyond their effects on blood pressure (BP), but their widespread use is limited by their tendency to provoke hyperkalemia. The comparative effects of ACEI and ARB on potassium handling have not been investigated. The objective of this study was to determine whether there are differences in dynamic renal potassium handling between ACEI and ARB in response to an oral potassium challenge. This was a randomized crossover study of candesartan versus lisinopril titrated to control BP followed by an inpatient study of renal potassium handling in 24 hypertensive patients with type II diabetes mellitus (DMII) and preserved renal function. Following an oral potassium challenge (0.75 mmol/kg), differences in hourly serum K (mmol/L), rate of urinary potassium excretion (UkV, micromol/min), and fractional excretion of potassium (FEK) were assessed by repeated-measures ANOVA. Hourly UkV(p = .45) and FEK (p = .19) were similar for candesartan and lisinopril, although FEK at 2 hours for candesartan tended to exceed that for lisinopril (.34 .04 vs. .26 .03) and approached significance (p = .096). UkVfor candesartan at hour 2 was 177 (26) and 121 (21) for lisinopril and also approached significance (p = .10). Serial serum potassium did not differ (p = .70). No statistical differences were discovered in renal potassium handling between candesartan and lisinopril in patients with DMII and preserved renal function. Whether there are differences between the drug classes in renal impairment remains to be determined.