mean of 4.5 antihypertensive drugs, led to a significant
decrease of systolic BP both in the office and on ABPM after
8 weeks of treatment. Spironolactone, compared to the
placebo, did not significantly influence the diastolic BP,
although a trend toward a decrease was observed for the
ABPM nighttime and office diastolic BP. Spironolactone led
to small but significant increases of serum potassium and
creatinine without adverse clinical consequences and was
Table 2.
Change of Patient Characteristics at 8 Weeks Compared to Baseline
Patient Characteristics
Spironolactone
(n
ϭ55)
Placebo
(n
ϭ56)
Between-Group
Difference*
P†
Systolic BP
ABPM daytime systolic BP, mm Hg
Ϫ9.3 (Ϯ12.6)
Ϫ3.9 (Ϯ12.1)
Ϫ5.4 (Ϫ10.0; Ϫ0.8)
0.024
ABPM nighttime systolic BP, mm Hg
Ϫ11.2 (Ϯ17.6)
Ϫ2.6 (Ϯ17.7)
Ϫ8.6 (Ϫ15.2; Ϫ2.0)
0.011
24-h ABPM systolic BP, mm Hg
Ϫ13.8 (Ϯ11.8)
Ϫ4.0 (Ϯ12.7)
Ϫ9.8 (Ϫ14.4; Ϫ5.2)
0.004
Office systolic BP, mm Hg‡
Ϫ14.6 (Ϯ15.6)
Ϫ8.1 (Ϯ14.8)
Ϫ6.5 (Ϫ12.2; Ϫ0.8)
0.011
Diastolic BP
ABPM daytime diastolic BP, mm Hg
Ϫ4.2 (Ϯ8.0)
Ϫ3.2 (Ϯ8.2)
Ϫ1.0 (Ϫ4.0; 2.0)
0.358
ABPM nighttime diastolic BP, mm Hg
Ϫ5.6 (Ϯ10.5)
Ϫ2.6 (Ϯ11.0)
Ϫ3.0 (Ϫ7.0; 1.0)
0.079
24-h ABPM diastolic BP, mm Hg
Ϫ4.2 (Ϯ7.0)
Ϫ3.2 (Ϯ7.7)
Ϫ1.0 (Ϫ3.7; 1.7)
0.405
Office diastolic BP, mm Hg‡
Ϫ6.6 (Ϯ9.6)
Ϫ4.1 (Ϯ8.6)
Ϫ2.5 (Ϫ5.9; 0.9)
0.079
Pulse Pressure§
ABPM daytime pulse pressure, mm Hg
Ϫ5.1 (Ϯ8.4)
Ϫ0.7 (Ϯ8.3)
Ϫ4.4 (Ϫ7.5; Ϫ1.3)
0.007
ABPM nighttime pulse pressure, mm Hg
Ϫ5.6 (Ϯ12.9)
0.0 (
Ϯ10.4)
Ϫ5.6 (Ϫ10.0; Ϫ1.2)
0.005
24-h ABPM pulse pressure, mm Hg
Ϫ6.5 (Ϯ7.2)
Ϫ0.8 (Ϯ7.6)
Ϫ5.7 (Ϫ8.5; Ϫ2.9)
Ͻ0.001
Office pulse pressure, mm Hg‡
Ϫ8.0 (Ϯ11.2)
Ϫ4.0 (Ϯ11.8)
Ϫ4.0 (Ϫ8.3; 0.3)
0.056
Other Characteristics
Weight, kg
0.3 (
Ϯ1.6)
0.5 (
Ϯ2.6)
Ϫ0.2 (Ϫ1.0; 0.6)
0.772
Serum Na, mmol/L
Ϫ1 (Ϫ6; 3)
Ϫ1 (Ϫ5; 4)
0.0
0.135
Serum K, mmol/L
0.3 (
Ϫ0.5; 1.5)
0.0 (
Ϫ0.8; 0.6)
0.3
Ͻ0.001
Serum creatinine,
mol/L
7 (
Ϫ11; 22)
0 (
Ϫ11; 18)
7.0
Ͻ0.001
Microalbuminuria, mg/day
Ϫ4.4 (Ϫ257.0;11.0)
0.0 (
Ϫ87.0; 98.0)
Ϫ4.4
0.023
Proteinuria, g/day
0.0 (
Ϫ0.5; 0.1)
0.0 (
Ϫ0.3; 1.7)
0.0
0.221
Data are mean (SD) when normally distributed and median (5th and 95th percentile range) when they have non-normal
distributions.
*Difference between spironolactone and placebo group is expressed as difference in their means supplemented by 95% confidence
interval or as difference in medians when they have non-normal distributions.
†Statistical significance was tested by the Mann-Whitney U test.
‡Average of second and third office BP measurements.
§Calculated as systolic BP minus diastolic BP in all measured parameters.
Table 3.
Mean BP Differences of 24-Hour ABPM Systolic and Diastolic BP after 8 Weeks of
Spironolactone Treatment in Relation to Baseline Laboratory Parameters
Baseline Parameter
First Tertile*
Second Tertile*
Third Tertile*
P†
Potassium, mmol/L
Յ3.9
3.9 – 4.37
Ͼ4.37
Systolic BP
Ϫ13.6 (Ϫ31.0; 2.1)
Ϫ10.5 (Ϫ29.0; 13.0)
Ϫ6.5 (Ϫ36.0; 13.0)
0.066
Diastolic BP
Ϫ7.0 (Ϫ17.6; 5.9)
Ϫ5.0 (Ϫ14.6; 7.0)
0.0 (
Ϫ25.0; 11.0)
0.183
Serum aldosterone, ng/L
Յ74
74–123
Ͼ123
Systolic BP
Ϫ13.0 (Ϫ36.0; 13.0)
Ϫ9.0 (Ϫ29.0; 13.0)
Ϫ8.0 (Ϫ28.0; 6.6)
0.615
Diastolic BP
Ϫ3.0 (Ϫ25.0; 8.0)
Ϫ6.0 (Ϫ17.6; 11.0)
Ϫ2.1 (Ϫ14.6; 7.6)
0.524
ARR
Յ7
7–45
Ͼ45
Systolic BP
Ϫ4.0 (Ϫ36.0; 13.0)
Ϫ13.0 (Ϫ31.0; 13.0)
Ϫ15.0 (Ϫ28.0; 2.1)
0.019
Diastolic BP
0.0 (
Ϫ25.0; 11.0)
Ϫ5.0 (Ϫ14.0; 8.0)
Ϫ7.0 (Ϫ17.6; 5.9)
0.049
PRA, ng/ml/h
Յ0.12
0.13–1.34
Ͼ1.34
Systolic BP
Ϫ19.0 (Ϫ31.0; 2.1)
Ϫ12.0 (Ϫ29.0; 13.0)
Ϫ4.0 (Ϫ36.0; 13.0)
0.006
Diastolic BP
Ϫ6.0 (Ϫ17.6; 5.9)
Ϫ5.0 (Ϫ14.6; 8.0)
0.0 (
Ϫ25.0; 11.0)
0.107
*Twenty-four– hour systolic and diastolic ABPM was described by the median and 5–95% percentile range.
†Statistical significance was evaluated by the Kruskal-Wallis test.
Va´clavík et al
Spironolactone in Resistant Hypertension
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well tolerated, and the number of side effects was comparable
to the placebo.
To our knowledge, this is the first randomized trial to
assess the antihypertensive effects of low-dose spironolac-
tone in patients with truly drug-resistant hypertension. Previ-
ous uncontrolled observational trials showed a substantial BP
reduction after the addition of spironolactone (ranging from
21.7 to 25 mm Hg systolic and 8.5 to 12.5 mm Hg diastolic
office BP) in patients treated with at least 2 or 3 antihyper-
tensive drugs.
8 –12
However, various confounding factors
could significantly influence the results, and with the absence
of a control group, the cause-and-effect relationship as well as
safety could not be established.
13,20
Compared to the previous observational trials, the magnitude
of average fall of BP in the spironolactone group compared to
the placebo was smaller. In a similar randomized trial with black
patients, using a diuretic and calcium channel blocker, the
addition of 25 mg of spironolactone led to a mean BP decrease
of 4.6/1.8 mm Hg after 9 weeks, and the reduction of diastolic
BP also did not reach statistical significance.
21
The lesser than expected effect of spironolactone on
diastolic BP in our trial may be partially explained by the
relatively low baseline diastolic BP (mean office diastolic BP
92 mm Hg, mean daytime ABPM diastolic BP 82 mm Hg),
with a significant proportion of patients (38%) having iso-
lated systolic hypertension. Recently, spironolactone has
been shown to reduce pulse pressure to a greater extent when
compared to dual blockade of the renin-angiotensin-aldoste-
rone system, which resulted in unchanged office diastolic BP
after 12 weeks.
22
Besides the diuretic effect of spironolac-
tone, its reduction of vascular stiffness probably plays a major
role in patients with resistant hypertension, contributing to
systolic BP reduction and decrease of pulse-wave velocity
and augmentation index,
23,24
and could explain the more
profound effect of spironolactone on systolic BP rather than
diastolic BP. As pulse pressure is an independent cardiovas-
cular risk factor and predictor of coronary artery disease
mortality in persons over the age of 50,
25–27
our observation
of the positive effect of spironolactone on pulse pressure
could be of great importance for future treatment of older
patients with isolated systolic hypertension.
The appropriate dosing range for spironolactone has not
been well defined in resistant hypertension.
20
According to
recent meta-analysis, there may be a dose response effect
with spironolactone up to 50 mg/day in patients with hyper-
tension, and higher doses
Ͼ50 mg/day do not produce further
reductions of BP.
5
It is possible that the increase of the
spironolactone dose to 50 mg/day could have led to a more
substantial decrease of BP.
The maximal hypotensive effect of spironolactone requires
3 to 4 weeks to be fully expressed in patients with mild
hypertension
28
and 7 weeks in patients with resistant hyperten-
sion.
21
Therefore, we feel that the designed length of our trial, 8
weeks, was sufficient for the full effect of spironolactone to
show.
The mild increase of serum potassium and creatinine with
spironolactone was expected. It needs to be stressed that the
majority of recruited patients had normal renal functions with
only 20% of patients exceeding the baseline creatinine upper
reference limit 104
mol/L. The risk of hyperkalemia and
worsening of renal functions would be higher if spironolac-
tone was used in patients with chronic kidney disease,
especially with a glomerular filtration rate
Ͻ45 mL/min and
serum potassium
Ͼ4.5 mmol/L.
29
Previous trials reported conflicting data about whether the
BP response to spironolactone can be predicted by baseline
aldosterone, ARR, or baseline potassium.
10, 21, 23, 30,31
In our
trial, the BP response to spironolactone treatment in patients
with baseline ARR
Յ7 and PRA Ͼ1.34 ng/mL per hour was
significantly worse than the BP response of patients with
ARR
Ͼ7 and PRA Յ1.34 ng/mL per hour. This could
possibly help to identify the patients for which treatment with
spironolactone is most effective.
Antihypertensive drugs were not discontinued before blood
sampling in accordance with current guidelines,
19
which
might have affected the measured values of ARR and may be
a limitation of this study, but we believe that this approach is
more easily generalizable and practical to adopt in everyday
practice.
Further limitation of our study is the relatively small
sample size. We calculated, based on our data, that we would
need to recruit almost 300 patients to reach statistical signif-
icance for diastolic BP reduction, which would require
broader clinical settings and additional funding.
Perspective
This randomized, double-blind, placebo-controlled trial
shows that spironolactone is an effective drug to lower
systolic BP in patients with resistant arterial hypertension. It
also shows that the greatest BP response can be expected in
patients with ARR
Ͼ7 and PRA Յ1.34 ng/mL per hour.
Since spironolactone is a cheap and widely available drug, its
use could lead to an improved BP control in the global
perspective. Whether spironolactone also significantly re-
duces the diastolic BP and its positive effect on BP leads to
a decreased number of cardiovascular events and decreased
mortality needs to be explored in further studies.
Acknowledgments
We thank Dagmar Strnkova´, Pavla Doupalova´, and Ilona Benusˇova´
for assistance with data collection.
Sources of Funding
This work was supported by a restricted grant from the Czech
Society for Hypertension (which provided 89% of funds) and Richter
Gedeon Ltd, Czech Republic, which provided the remaining 11% of
funds to cover trial insurance and also the spironolactone for the
preparation of the randomized medication.
Disclosures
None.
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