Background Inhibition of the renin-angiotensin system is known to raise ser
um potassium [K+] levels in patients with renal insufficiency or diabetes.
No study has evaluated the comparative effects of an angiotensin-converting
enzyme (ACE) inhibitor versus an angiotensin receptor blocker (ARB) on the
changes in serum [K+] in people with renal insufficiency.
Methods. The study was a multicenter, randomized, double crossover design,
with each period lasting one month. A total of 35 people (21 males and 14 f
emales, 19 African Americans and 16 Caucasian) participated, with the mean
age being 56 +/- 2 years. Mean baseline serum [K+] was 4.4 +/- 0.1 mEq/L. T
he glomerular filtration rate (GFR) was 65 +/- 5 mLmin/1.73 m(2), and blood
pressure was 150 +/- 2/88 +/- 1 mm Hg. The main outcome measure was the di
fference from baseline in the level of serum [K+], plasma aldosterone, and
GFR following the initial and crossover periods.
Results. For the total group, serum [K+] changes were not significantly dif
ferent between the lisinopril or valsartan treatments. The subgroup with GF
R values of less than or equal to 60 mL/min/1.73 m(2) who received lisinopr
il demonstrated significant increases in serum [K+] of 0.28 mEq/L above the
mean baseline of 4.6 mEq/L (P = 0.04). This increase in serum [K+] was als
o accompanied by a decrease in plasma aldosterone (P = 0.003). Relative to
the total group, the change in serum [K+] from baseline to post-treatment i
n the lisinopril group was higher among those with GFR values of less than
or equal to 60 mL/min/1.73 m2. The lower GFR group taking valsartan, howeve
r, demonstrated a smaller rise in serum [K+], 0.12 mEq/L above baseline (P
= 0.1), a 43% lower value when compared with the change in those who receiv
ed lisinopril. This blunted rise in [K+] in people taking valsartan was not
associated with a significant decrease in plasma aldosterone (P = 0.14).
Conclusions. In the presence of renal insufficiency, the ARE valsartan did
not raise serum [K+] to the same degree as the ACE inhibitor lisinopril. Th
is differential effect on serum [K+] is related to a relatively smaller red
uction in plasma aldosterone by the ARE and is not related to changes in GF
R. This study provides evidence that increases in serum [K+] are less likel
y with ARE therapy compared with BCE inhibitor therapy in people with renal
insufficiency.