Pharmacokinetics and pharmacodynamic effects of the angiotensin II antagonist valsartan at steady state in healthy, normotensive subjects

Abstract

Objective:
Pharmacokinetics, pharmacodynamic effects and tolerability of 200 mg valsartan, once-daily for 8 days, were investigated in 16 healthy, normotensive volunteers on a normal sodium diet.

Methods:
This was a double-blind, placebo-controlled, randomized crossover study. Drug concentrations in plasma and urine, angiotensin II (Ang II) concentrations in plasma, systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR) in the supine position and 3 min after passive head-up tilting, as well as safety parameters (ECG, clinical chemistry and hematology, renal water and electrolyte excretion) were measured over 24 h after the first dose (day 1) and at steady state on day 8.

Results:
Absorption and distribution of valsartan were rapid (Cmax, 2 h; t1/2 lambda 1 < 1 h), followed by a slower terminal elimination phase (t1/2 lambda 2, 6 h) on days 1 and 8, with little accumulation in plasma (increase of 20% on day 8). Less than 10% of the dose was excreted unchanged in urine. The increase in plasma Ang II (Cmax, 6 h) was significantly enhanced at steady state. Supine SBP and DBP significantly decreased on day 8 only, by an average of -3.6 and -2.4 mmHg, respectively, versus placebo, without a concomitant increase in HR. Upon passive tilting, the increase in DBP, normally reinforced by sympathetic renin release, was slightly but significantly blunted on day 1 (-2.0 mmHg) and day 8 (-4.0 mmHg) of treatment with valsartan versus placebo. The orthostatic reflex increase in HR was slightly enhanced compared with placebo by an average of 2.8 beats min-1 on day 1 and by 2.9 beats.min-1 on day 8. Valsartan was well tolerated and had no influence on ECG, clinical laboratory parameters, and water, electrolyte and uric acid excretion.

Conclusions:
Pharmacokinetics of valsartan are unchanged after multiple once-daily dosing, with little (expected) accumulation in plasma. Effects of 200 mg valsartan on blood pressure in healthy subjects on a normal sodium intake are small and become more prominent after repeated dosing. Indirect evidence of AT1 blockade by valsartan is demonstrated by an increase of plasma Ang II and by a blunted DBP response to passive tilting. The decrease in blood pressure at steady state enhances the increase in plasma Ang II. Valsartan is well tolerated and is devoid of effects on water, electrolyte and uric acid excretion at 200 mg per day in healthy normotensive volunteers.

Full text

PHARMACODYNAMICS
P. Mu
Èller áG. Flesch áM. de Gasparo
M. Gasparini áH. Howald
Pharmacokinetics and pharmacodynamic effects of the angiotensin II
antagonist valsartan at steady state in healthy, normotensive subjects
Received: 5 December 1996 / Accepted in revised form: 28 February 1997
Abstract Objective: Pharmacokinetics, pharmacody-
namic eects and tolerability of 200 mg valsartan, once-
daily for 8 days, were investigated in 16 healthy,
normotensive volunteers on a normal sodium diet.
Methods: This was a double-blind, placebo-controlled,
randomized crossover study. Drug concentrations in
plasma and urine, angiotensin II (Ang II) concentrations
in plasma, systolic (SBP) and diastolic (DBP) blood
pressure, heart rate (HR) in the supine position and
3 min after passive head-up tilting, as well as safety pa-
rameters (ECG, clinical chemistry and hematology, renal
water and electrolyte excretion) were measured over 24 h
after the ®rst dose (day 1) and at steady state on day 8.
Results: Absorption and distribution of valsartan were
rapid (C
max
, 2 h; t
k1
< 1 h), followed by a slower
terminal elimination phase (t
k2
, 6 h) on days 1 and 8,
with little accumulation in plasma (increase of 20% on
day 8). Less than 10% of the dose was excreted un-
changed in urine. The increase in plasma Ang II (C
max
,
6 h) was signi®cantly enhanced at steady state. Supine
SBP and DBP signi®cantly decreased on day 8 only, by
an average of )3.6 and )2.4 mmHg, respectively, versus
placebo, without a concomitant increase in HR. Upon
passive tilting, the increase in DBP, normally reinforced
by sympathetic renin release, was slightly but signi®-
cantly blunted on day 1 ()2.0 mmHg) and day 8
()4.0 mmHg) of treatment with valsartan versus place-
bo. The orthostatic re¯ex increase in HR was slightly
enhanced compared with placebo by an average of 2.8
beats ámin
)1
on day 1 and by 2.9 beats ámin
)1
on day 8.
Valsartan was well tolerated and had no in¯uence on
ECG, clinical laboratory parameters, and water, elec-
trolyte and uric acid excretion.
Conclusions: Pharmacokinetics of valsartan are un-
changed after multiple once-daily dosing, with little
(expected) accumulation in plasma. Eects of 200 mg
valsartan on blood pressure in healthy subjects on a
normal sodium intake are small and become more
prominent after repeated dosing. Indirect evidence of
AT
1
blockade by valsartan is demonstrated by an in-
crease of plasma Ang II and by a blunted DBP response
to passive tilting. The decrease in blood pressure at
steady state enhances the increase in plasma Ang II.
Valsartan is well tolerated and is devoid of eects on
water, electrolyte and uric acid excretion at 200 mg per
day in healthy normotensive volunteers.
Key words Angiotensin II, Valsartan; AT
1
receptor
antagonist, healthy volunteers, pharmacokinetics, renin-
angiotensin system, blood pressure, passive tilting
Introduction
Valsartan (CGP 48933) is a potent selective antagonist
of the angiotensin II receptor subtype AT
1
[1, 2, 3]. This
receptor mediates all the known eects of angiotensin II
(Ang II) on the cardiovascular system [4]. AT
1
blockade
with valsartan oers a highly speci®c approach towards
treatment of arterial hypertension [2, 5±7].
The concept of speci®c AT
1
receptor blockade has
been proven in healthy normotensive volunteers after
single oral doses of 40 and 80 mg valsartan [8] and after
repeated once-daily dosing of 80 mg valsartan for 7 days
[9]. In these studies, inhibition of the pressor eect of
exogenous Ang II by valsartan provided a direct mea-
sure of receptor blockade. The AT
1
receptor was maxi-
mally blocked 2 h after dosing (75±100% inhibition),
and blockade was maintained up to 24 h after a single
dose (25±60% inhibition) [8, 9]. Receptor blockade was
accompanied by an increase in plasma renin activity
(PRA), with a maximum eect at 4±6 h and lasting for
24 h after single doses of 40 and 80 mg [8].
This increase in PRA is an expected ®nding after
blockade of the AT
1
receptor due to inhibition of the
negative feedback loop. In addition, re¯ex sympathetic
Eur J Clin Pharmacol (1997) 52: 441±449 ÓSpringer-Verlag 1997
P. Mu
Èller (&)áG. Flesch áM. de Gasparo
M. Gasparini áH. Howald
Clinical Pharmacology, K-147.3.32, Novartis Pharma AG,
CH-4002 Basel, Switzerland
Fax +41 (61) 696 55 42

release of renin may be induced by a decrease in blood
pressure. Subsequent to the increase in PRA, Ang II
plasma levels also increase, as shown in early human
studies with the speci®c AT
1
antagonist losartan after
single [10] and multiple [11] administration to normo-
tensive volunteers.
The aims of this phase I study were to investigate the
tolerability, the pharmacokinetics and the pharmaco-
dynamic eects (plasma Ang II concentration, blood
pressure and heart rate) of 200 mg valsartan in healthy
volunteers after single administration and at steady state
(once-daily dosing for 8 days). The 200-mg dose is 2.5
times the recommended usual therapeutic daily dose for
the treatment of hypertension. The results of a prelimi-
nary evaluation of this study have previously been pre-
sented as an abstract [12].
Methods
Study design, subjects and treatments
In this double-blind, placebo-controlled, randomized two-period
crossover study, 16 healthy male subjects on a normal sodium in-
take diet received 200 mg valsartan or placebo once daily for 8
days. Between treatments, a wash-out period of at least one week
was observed. Pharmacokinetic and pharmacodynamic evaluations
were performed after the ®rst dose (day 1) and at steady state (day
8). Randomization for the two treatment sequences was carried out
in blocks of four.
Prior to inclusion, subjects were screened for eligibility based on
a medical check-up including history, physical examination, ECG,
clinical chemistry, hematology, urinalysis, hepatitis B and HIV
serology, and a urine screen for drugs of abuse. No concomitant
drugs were allowed from 14 days prior to, and no alcohol from
24 h prior to the start of the study until 24 h after its completion.
The study was conducted in accordance with the ethical stan-
dards laid down in the 1989 Hong Kong amendment of the 1964
Declaration of Helsinki. The study protocol was approved by an
ethics committee. All subjects gave written consent for their par-
ticipation in the study.
The clinical supplies consisted of matching capsules containing
40 mg or 80 mg valsartan, or placebo. Each daily dose consisted of
three capsules, either two 80 mg plus one 40 mg valsartan capsule,
or three placebo capsules. The capsules were taken each morning
between 07:00 and 08:00 hours, on days 1 and 8 on an empty
stomach after an overnight fast, and on the other days after
breakfast.
Study procedures
Subjects were on an out-patient basis except on the treatment days
1 and 8 when they remained at the clinical research unit until 12 h
post-dose.
In the morning of study days 1 and 8, an indwelling cannula
was inserted into a forearm vein of the subjects and closed with a
heparin lock. After 15 min rest, the baseline measurements of su-
pine BP and HR were performed, a 12-lead ECG was recorded and
the blood samples for drug and Ang II concentrations measure-
ments were withdrawn. The subjects were then passively tilted to an
angle of 45°on a tilt table, and BP and HR were measured again
after 3 min in orthostatic (tilted) position. After voiding their
bladders, the subjects received the study medication together with
200 ml water. Further blood samplings and recordings were per-
formed until 24 h after drug administration, as described below.
Before each set of measurements, a supine rest of 15 min was
observed, otherwise the subjects were free to move around on the
ward.
Food and ¯uid intake were standardized until 10 h after dosing:
200 ml water was given at 1 and 3 h, breakfast including 300 ml
caeine-free coee at 2 h, lunch including 300 ml water at 4 h, and
another 300 ml caeine-free coee at 7 h after drug administration.
The total ¯uid volume given to the subjects between the time of
drug administration and 10 h thereafter was 1.5 l. Thereafter,
subjects had free access to ¯uid until the next morning.
Pharmacokinetic measurements
Blood samples (5 ml) for the determination of valsartan in plasma
were obtained at 1, 2, 3, 4, 6, 8, 10 and 24 h after dosing, directly
into sodium-heparinized vacuum tubes. The blood was immedi-
ately centrifuged at 2200 gfor 5 min at 4 °C. The plasma was
frozen and stored at )18 °C until analysis.
Urine was collected quantitatively from 0±2, 2±4, 4±8 and 8±
24 h after dosing. The weight of each fraction was recorded and an
aliquot of 10 ml was kept frozen at )20 °C until analysis for val-
sartan. A second 10-ml aliquot from each fraction was kept for the
measurement of urinary electrolytes and uric acid. The remaining
urine of each fraction was pooled (0±24 h) for the determination of
urea and creatinine.
Valsartan in plasma and urine was measured using high pres-
sure liquid chromatography (HPLC) with UV detection. After the
internal standard (CGP 48791) [13] had been added to the plasma
or urine samples, valsartan and the internal standard were isolated
by a solid-phase extraction on a Bond-Elut CH cartridge, with
methanol as the ®nal eluent. After evaporation of the solvent, the
residue was dissolved in the mobile phase (0.1% tri¯uoroacetic acid
[TFA] in acetonitrile/H
2
O, 45/55 v/v) and chromatographed on a
250 mm ´4 mm internal diameter column packed with Nucleosil
C18/10 lm. Chromatography was achieved by a binary isocratic
elution (0.1 % TFA in acetonitrile/H
2
O, 45/55 v/v), at a ¯ow rate
of the mobile phase of 1 ml ámin
)1
. In extracts from plasma and
urine, valsartan and the internal standard were detected by UV
monitoring at 215 nm.
The following pharmacokinetic variables were determined:
C
max
= highest observed valsartan concentration in plasma;
t
max
= time to reach C
max
; AUC
(0±24 h)
= area under the plasma
concentration-time curve for the time 0±24 h post-dose, calcu-
lated by the linear trapezoidal rule; t
k2
= half-life associated
with the terminal elimination phase, calculated by linear regres-
sion analysis of the semilogarithmic concentration-time data be-
tween 8 and 24 h; AUC = AUC for the time 0 to in®nity on
day 1, by adding AUC
(0±24 h)
+C
24 h
á(0.693 át
k2
)1
)
)1
; Ratio
R
(plasma)
= AUC
(0±24 h)
day 8/(AUC day 1); Ae
(0±24 h)
= amount
of drug excreted unchanged in urine, calculated as the sum of
drug excreted in the dierent sampling intervals between 0
and 24 h after administration; Ratio R
(urine)
=Ae
(0±24 h)
day 8/
(Ae
(0±24 h)
day 1).
Pharmacodynamic measurements
For the determination of Ang II plasma concentrations, 5 ml blood
was collected at 2, 4, 6, 8, 10 and 24 h after dosing into evacuated
tubes containing 250 ll of an inhibitor solution, resulting in an end
concentration of 17 lmol ál
)1
ethanol, 2.5 mmol ál
)1
O-phenan-
tholine, 6.2 mmol ál
)1
EDTA, 5 lmol ál
)1
CGP 38560A (renin in-
hibitor) and 13 lmol ál
)1
enalaprilat per sample. The tubes were
kept chilled in ice-water before and immediately after sampling.
The blood was centrifuged without delay at 2200 gfor 5 min at
4°C and the plasma snap-frozen on dry ice. The samples were
stored at )80 °C until analysis. Conventional radio-immuno-assay
(RIA) methods were used for measuring plasma Ang II, with a
limit of detection of 1 fmol áml
)1
. Ang II was extracted on Bond-
Elut cartridges (Analytichem, Harbor City, Calif.) prior to analysis.
There was no separation of the various angiotensin-related peptides
by HPLC.
442

BP and HR were measured at each time of blood sampling for
Ang II, using the arm opposite to the venous cannula with a Di-
namap monitor model 1846 SX (Critikon Inc., Tampa, Fla., USA)
after 15 min rest in supine position and 3 min after passive head-up
tilting to an angle of 45°on a tilting table.
Evaluations of tolerability and safety
Adverse experiences were recorded throughout the 8 days treatment
in each study period. Routine clinical laboratory an analysis, in-
cluding serum electrolytes, renal and hepatic function parameters,
routine hematology including RBC, WBC and dierential count and
urinalysis using a dip-stick method followed by microscopic evalu-
ation of the sediment, was performed on study days 1, 4 and 8.
Body weight and 12-lead ECGs were recorded on days 1, 4 and
8 of each treatment period.
Urinary sodium, potassium and uric acid excretion were mea-
sured in each urine fraction, and urinary creatinine and urea ex-
cretion were measured over 24 h on days 1 and 8. Creatinine
clearance (C
CR
) was calculated from the concentrations of creati-
nine in serum (c
CR serum
) and urine (c
CR urine
) as: C
CR
=c
CR
urine
á¯ow
urine
á(c
CR serum
)
)1
.
Statistical analysis
The statistical analysis was performed using the changes of blood
pressure and heart rate from pre-treatment baseline (=value at
time zero on day 1) in both treatment periods. No adjustment was
made for dierences in baseline values for Ang II between treat-
ment periods.
The contrasts of interest were the dierences between the val-
sartan treatment mean and the placebo mean on days 1 and 8,
respectively (treatment eect), and the dierence of the treatment
eect between days 8 and 1 (treatment by day interaction).
Statistical analysis was performed according to a linear model
approach suitable for the crossover design, with treatment (200 mg
valsartan or placebo), day, hour, sequence and period considered as
factors with ®xed eects, and with subject taken as a random eect.
Results
Demographics of study subjects
The 16 male subjects had a mean age of 36 years (range:
23±53), a mean weight of 76 kg (range: 62±88) and a
mean height of 179 cm (range: 166±194). All sixteen
subjects completed both study periods, and no missing
data or samples were identi®ed.
Pharmacokinetics
The method was validated by analysis of spiked human
plasma and urine samples. Forty human plasma samples
and 19 human urine samples spiked with valsartan were
analyzed together with the samples from this study. The
concentration range was 0.75±13.5 mg ál
)1
in plasma and
1.52±23.3 mg ál
)1
in urine. In spiked 1-ml human plasma
samples, a concentration of 0.75 mg ál
)1
could be ana-
lyzed with a coecient of variation (CV) of 13.70%, the
deviation from theory was 2.41%; therefore, the limit of
quantitation (LOQ) was below 0.7 mg ál
)1
in plasma and
below 1.5 mg ál
)1
in urine [14].
With the exception of two subjects (nos. 04 and 15),
valsartan was detected in all samples at 24 h post-dosing
on day 1, and in all samples at trough and 24 h on day 8.
At
k2
could not be determined for subjects 04 and 15
on day 1.
Mean valsartan concentration-time pro®les are illus-
trated in Fig. 1, and the derived pharmacokinetic pa-
rameters are listed in Table 1. Mean AUC and C
max
values were similar on days 1 and 8. C
max
was observed
between 1 and 6 h (median 2 h) after administration on
days 1 and 8. The decay phase of the plasma concen-
tration±time curve was characterized by a bi-exponential
course with a fast distribution phase (t
k1
< 1 h) and a
slower terminal elimination phase (t
k2
= 6 h), both
after the single dose and at steady state. The mean ac-
cumulation factor R in plasma was 1.21(0.45) (SD), with
individual values of <1 in ®ve subjects and >1 in nine
subjects.
Only a small fraction of the administered dose of
valsartan was excreted unchanged in urine during 24 h.
On day 1, on average, 4.7% of the dose was excreted
Fig. 1 Mean (SD) valsartan con-
centrations in plasma on days 1
and 8 of once-daily administra-
tion of 200 mg of valsartan to 16
healthy volunteers
443

(range 1.78±7.93%) and, at steady state, 6.4 percent of
the dose (range 4.22±9.99%). The accumulation factor,
R, in urine of 1.57(0.62) (SD) was consistent with the
accumulation factor calculated for plasma.
Plasma angiotensin II concentration
Baseline Ang II concentrations in plasma were repro-
ducible with mean values of 5.7 (4.6) (SD) fmol áml
)1
before valsartan on day 1, and 4.8 (2.5) and 6.2 (3.9)
fmol áml
)1
before placebo on days 1 and 8, respectively.
During placebo treatment the diurnal ¯uctuation of
plasma Ang II was small, with maximum mean con-
centrations at 6 h of 7.1 (4.1) fmol áml
)1
on day 1 and
8.3 (4.7) fmol áml
)1
on day 8.
After valsartan treatment, there was a pronounced
and statistically signi®cant increase of plasma Ang II,
reaching a maximum at 6 h after dosing on both day 1
and day 8 (Fig. 2), i.e., about 4 h after the plasma drug
concentrations had reached C
max
(Fig. 1). The treatment
eect on Ang II was de®nitely more pronounced on day
8, i.e., after repeated dosing (P= 0.0001, Table 3). On
day 1, the maximum increase in Ang II concentra-
tions above placebo at 6 h after dosing was 34.9 (41.8)
fmol áml
)1
(P= 0.0006), and on day 8 was 118.1 (63.7)
fmol áml
)1
(P= 0.0001). On both days, Ang II de-
creased thereafter until 10 h after administration, but
then remained above placebo at a constant level until
24 h (Fig. 2), despite the further fall in plasma valsartan
concentration (Fig. 1). This persistent rise in the plasma
Ang II concentration between 10 and 24 h after dosing
was relatively small on day 1 (by about 7 fmol áml
)1
above placebo at 10 h and 24 h), but more pronounced
at steady state on day 8 [by about 24 fmol áml
)1
at
trough (0 h) as well as at 10 h and 24 h after drug ad-
ministration].
Blood pressure and heart rate
Passive tilting of the subjects at baseline to an angle of 45°
resulted in distinct hemodynamic changes: an increase in
DBP by an average of 4±5 mmHg and an increase of HR
by an average of 10±11 beats ámin
)1
(Table 2).
The mean changes of SBP, DBP and HR in supine
and tilted position from the pre-treatment baseline, after
valsartan and placebo are shown in Fig. 3. The mean
(SD) baseline values for the above parameters are given
Table 1 Mean (SD) pharmaco-
kinetic parameters on days 1
and 8 after once-daily adminis-
tration of 200 mg valsartan to
16 healthy volunteers.
a
median
value;
b
n=14, without subject
no. 4 and 15;
c
n=15, without
subject no. 16
Day 1 Day 8 Day8/Day 1
Mean (SD) Mean (SD) Mean (SD)
C
max
(mg ál
)1
) 3.46 (1.44) 3.94 (1.38)
t
max
(h) 2
a
2
a
t
k2
(h) 5.78
b
(2.41) 6.19
c
(1.98)
AUC
(0±24 h)
(h ámg ál
)1
) 21.33 (10.22) 25.75 (7.63)
AUC (h ámg ál
)1
) 24.38 (9.76)
R
(plasma)
1.21
b
(0.45)
Ae
(0±24 h)
(mg) 9.34 (4.13) 12.76 (3.46)
Ae
(0±24 h)
(% of dose) 4.68 (2.06) 6.38 (1.73)
R
(urine)
1.57 (0.62)
Fig. 2 Mean (SD) Ang II con-
centrations in plasma on days 1
and 8 of once-daily administra-
tion of 200 mg of valsartan and
placebo to 16 healthy volunteers
444

in Table 2 and the results of the statistical evaluation in
Table 3.
BP showed a distinct diurnal ¯uctuation both on
placebo and on active drug (Fig. 3), with a decrease of
SBP and DBP during the morning and early afternoon,
followed by a rise towards evening. HR decreased during
the ®rst 2 h, followed by an increase to a maximum at 6 h
after dosing and a decline thereafter. The baseline mea-
surements were taken between 07.00 and 08.00 hours.
In a supine position, valsartan had no signi®cant ef-
fect on SBP, DBP and HR on day 1 compared with
placebo. On day 8, supine SBP and DBP were slightly
but signi®cantly decreased compared with placebo by an
average of )3.6 mmHg (P= 0.0002) and )2.4 mmHg
Table 2 Mean (SD) pre-dose baseline values of blood pressure (BP) and heart rate on study day 1, measured before 200 mg of valsartan
and placebo in 16 healthy volunteers after 15 min supine rest and 3 min after passive head-up tilting to 45°
Baseline before valsartan Baseline before placebo
Supine Tilted Supine Tilted
Mean SD Mean SD Mean SD Mean SD
Systolic BP [mmHg] 118.0 (12.5) 118.8 (10.8) 121.3 (11.2) 120.4 (11.7)
Diastolic BP [mmHg] 72.4 (8.9) 78.7 (7.2) 74.3 (7.4) 78.8 (7.3)
Heart rate [beats ámin
)1
] 61.7 (9.0) 71.6 (6.8) 62.5 (10.1) 73.9 (10.4)
Fig. 3 Mean (SD) changes
from baseline of supine and
tilted systolic and diastolic
blood pressure and heart rate
on days 1 and 8 of once-daily
administration of 200 mg of
valsartan and placebo to 16
healthy volunteers. For baseline
values see Table 2
445

(P= 0.0004), respectively. Valsartan had no eect on
supine HR on day 8 (Table 3).
The increase of DBP induced by tilting was slightly
less after valsartan than after placebo, by an average of
)2.0 mmHg (P= 0.0033) on day 1 and by )4.0 mmHg
(P= 0.0001) on day 8. The dierence in this eect be-
tween days 1 and 8 was statistically signi®cant
(P= 0.0475). Also, the increase in SBP induced by
tilting was slightly reduced after valsartan compared
with placebo, by an average of )2.1 mmHg (P= 0.05)
on day 1 and by )2.9 mmHg (P= 0.0079) on day 8.
This slight blunting of the blood pressure response to
passive tilting after treatment was accompanied by an
enhanced orthostatic rise in HR compared with placebo,
by 2.8 beats ámin
)1
(P= 0.0104) on day 1 and by 2.9
beats ámin
)1
(P= 0.0084) on day 8.
Tolerability and safety
Adverse experiences (AEs) were generally infrequent
and mostly of mild to moderate severity. Altogether, in
256 study days (128 days each with active and placebo
treatment), there were 25 reports of AEs, 13 on active
treatment and 12 on placebo. The most common AE
was headache (8 days on active, 7 days on placebo).
Headache was most frequently reported on study day 1
and/or day 8. Headache was severe on two occasions
and accompanied by vomiting in two subjects, one on
active drug and one on placebo. Other gastrointestinal
symptoms such as nausea, abdominal distress and di-
arrhea were present in three subjects on 6 treatment
days, two times on active drug and four times on pla-
cebo. One subject complained about torticollis on two
days of active treatment.
There were no changes in the clinical laboratory pa-
rameters, including serum electrolytes and uric acid, and
markers of renal and hepatic function. Valsartan also
had no in¯uence on ECG morphology and ECG time
intervals (P wave duration, PQ interval, QRS duration,
QT interval).
No eect of valsartan was observed on 24-h urinary
volume, urinary excretion of sodium, potassium, uric
acid and urea, or creatinine clearance (Table 4). There
was also no dierence in water, electrolyte or uric acid
excretion between valsartan and placebo in any of the
single urine fractions collected 0±2, 2±4, 4±8 and 8±24 h
after administration.
Table 3 Results of statistical analysis. Each variable listed, except
Ang II, represents the dierence from baseline (i.e., the value at
time zero of day 1). The ®rst two DIFF columns provide the dif-
ference between the 200 mg valsartan treatment mean and the
placebo mean, on day 1 and day 8, respectively. The corresponding
P-values are to test for a treatment eect on those two days. DIFF
in the last column refers to the dierence between the previous
dierences (day 8 )day 1). The corresponding P-values are to test
for a signi®cant dierence between the treatment eects on day 8
and day 1; low P-values in this case are indicative of a signi®cant
treatment by day interaction
Treatment eect Treatment*day interaction
Day 1 Day 8 Day 8 )1
Pvalue DIFF Pvalue DIFF Pvalue DIFF
SBP supine [mmHg] 0.9779 )0.03 0.0002 )3.61 0.0092 )3.58
SBP tilted [mmHg] 0.0500 )2.12 0.0079 )2.88 0.6185 )0.76
DBP supine [mmHg] 0.1202 )1.05 0.0004 )2.41 0.1569 )1.36
DBP tilted [mmHg] 0.0033 )2.04 0.0001 )3.97 0.0475 )1.94
HR supine [beats ámin
)1
] 0.0639 1.69 0.4263 0.72 0.4532 )0.96
HR tilted [beats ámin
)1
] 0.0104 2.79 0.0084 2.88 0.9583 0.08
Ang II at 6 h [fmol áml
)1
] 0.0006 35 0.0001 118 0.0001 83
Table 4 Mean (SD) renal function parameters measured on study days 1 and 8 during 24 h after 200 mg of valsartan and placebo in
sixteen healthy volunteers
200 mg valsartan Placebo
Day 1 Day 8 Day 1 Day 8
Mean SD Mean SD Mean SD Mean SD
Urine volume [1] 2.34 (0.79) 2.23 (0.62) 2.34 (0.75) 2.54 (0.59)
Urine ¯ow [ml ámin
)1
] 1.65 (0.55) 1.54 (0.43) 1.62 (0.53) 1.76 (0.41)
Na
+
excretion [mmol] 221 (58) 193 (61) 204 (56) 194 (66)
K
+
excretion [mmol] 93.0 (25.2) 89.6 (23.0) 88.3 (20.9) 90.8 (26.8)
Uric acid excretion [mmol] 3.62 (0.61) 3.65 (0.53) 3.46 (0.53) 3.61 (0.77)
Urea excretion [mmol] 370 (67) 392 (105) 382 (80) 359 (96)
C-creatinine [ml ámin
)1
] 106 (12) 105 (16) 105 (11) 107 (15)
446

Discussion and conclusions
The pharmacokinetic parameters C
max
,t
max
, AUC and
t
k2
after a single dose of 200 mg valsartan, determined
in the present study, are in line with ®ndings from other
single dose studies with 80 mg valsartan given as a
capsule [2, 9, 15]. Valsartan was rapidly absorbed and
the decay phase of the plasma concentration±time curve
was characterized by a bi-exponential course, with a
rapid distribution phase (t
k1
< 1 h) and a slower
elimination phase (t
k2
= 6 h). From this half-life, it
may be estimated that steady-state plasma concentra-
tions had already been reached after the second dose.
The kinetics of absorption, distribution and elimi-
nation were unchanged after repeated dosing, with
similar t
max
and t
k2
values on days 1 and 8. Compar-
isons of AUC values after the ®rst dose and on day 8
revealed only a small accumulation of about 20% when
valsartan is given once per day. Less than 10% of the
administered dose was excreted as unchanged drug in
urine.
After the ®rst dose of valsartan, plasma Ang II con-
centrations increased to a maximum at 6 h and were
maintained above placebo levels from 10 to 24 h after
dosing, despite the further decline in plasma levels of
valsartan. This ®nding is in agreement with Ang II
challenge experiments, showing that the relationship
between drug levels in plasma, AT
1
receptor blockade
and the subsequent negative feedback response of the
renin-angiotensin system (RAS) is not instantaneous,
but follows a counterclockwise hysteresis curve with a
time shift of the RAS response: maximum AT
1
receptor
blockade is present at the time of maximum drug con-
centration in plasma, but the blockade is maintained up
to 24 h after dosing despite decreasing drug concentra-
tions [8, 9]; the increase in plasma renin activity lags
behind maximum drug levels by about 2±4 hours and is
also present until 24 h [8]. This indicates that there is a
dynamic equilibrium between the central compartment,
represented by the plasma concentration of valsartan,
receptor blockade, and the feedback eect (increase in
PRA and Ang II).
After 8 days of treatment, both the pre- and post-
dose trough Ang II concentrations, as well as the max-
imum response, were further increased. This phenome-
non has also been observed in multiple dose experiments
with losartan [11, 16]. However, from Ang II challenge
experiments with losartan for 8 days [11] and valsartan
for 7 days [9], it appears that the enhanced response of
endogenous Ang II after multiple dosing is not related to
an enhanced blockade of the receptor. Other mecha-
nisms, apart from the negative feedback blockade, must
contribute to the enhanced increase in Ang II after
multiple doses: the decrease of SBP and DBP, which
becomes prominent in a supine position only after
multiple dosing (see below) might activate sympathetic
release of renin and add to the increase in Ang II at
steady state. The similar Ang II concentration at trough
(0 h) and 24 h after dosing suggests that these eects
might have been at steady state on day 8.
Blood pressure and heart rate showed distinct diurnal
¯uctuations on placebo which can be explained by the
speci®c experimental conditions: prolonged supine rest-
ing periods during the morning hours, and food intake
at 2 and 4 h after dosing, which promotes an increase in
HR. Valsartan had no eect on supine BP and HR after
the ®rst dose, but induced a small but statistically sig-
ni®cant decrease in supine SBP and DBP on day 8,
without an increase in resting HR.
Passive tilting of the body results in acute redistri-
bution of blood to the lower parts of the body (venous
pooling), causing a decrease in venous return (preload),
and a reduction of ventricular ®lling pressure and stroke
volume. The hemodynamic changes observed upon
passive tilting ± an increase in DBP and HR ± are acute
compensatory adaptations in order to maintain cardiac
output and cerebral perfusion [17]. They are promoted
by re¯ex sympathetic catecholamine release, but also
through acute activation of the RAS [18, 19]. The slight
reduction of the DBP-increase to tilting after valsartan,
compared with placebo, indicates that this renin-an-
giotensin component of the orthostatic response was
blunted by AT
1
receptor blockade. This eect was al-
ready present after the ®rst valsartan dose and was
accompanied by a slightly enhanced sympathetic acti-
vation of heart rate by about 3 beats ámin
)1
over pla-
cebo, compensating for the blunted increase of DBP.
Thus, in healthy subjects with an otherwise unstimulated
RAS, passive tilting was able to detect a blood pressure
response to AT
1
receptor blockade which was not de-
tectable in the supine position. However, the magnitude
of these eects was very small and may be observed only
under the very standardized condition of passive tilting
where venous pooling is maximal due to the elimination
of the muscle pump. No clinical signs of deregulation of
the orthostatic response were observed during the tilting
procedures, and no signs of orthostatic hypotension
have been reported in clinical trials with valsartan [5±7].
Valsartan had no eect on urinary uric acid excretion
and serum uric acid concentrations. For the AT
1
re-
ceptor antagonist losartan a dose-dependent uricosuric
eect associated with a decrease in serum uric acid has
been reported [20, 21, 22]. This short-lived uricosuric
eect of losartan appears to be independent of AT
1
re-
ceptor blockade [21] and is probably a speci®c eect of
the parent compound: losartan is rapidly absorbed
(C
max
, 1 h) and rapidly disappears from plasma (t

,2h)
with extensive biotransformation to an active metabolite
[23]. The active metabolite of losartan (E3174), which is
mainly responsible for the AT
1
receptor blocking eect
of losartan, has no uricosuric eect [24].
Among other renal eects, Ang II is involved in renal
water and electrolyte homeostasis, through stimulation
of proximal tubular sodium and water reabsorption, es-
pecially under conditions of volume or sodium depletion
[25, 26]. Modulation of renal AT
1
receptors has been
shown to mediate essentially all of the known intrarenal
447

eects of Ang II [27]. The possible role of renal AT
2
receptors in the control of renal function was investigated
in rats with speci®c AT
2
receptor ligands and appears to
depend on perfusion pressure: under conditions of nor-
mal perfusion pressure, renal AT
2
receptor-mediated
eects could not be con®rmed [28, 29], whereas an AT
2
receptor-mediated antinatriuretic eect has been postu-
lated from experiments with increased renal perfusion
pressure [30, 31]. In the present study, in human subjects
with a normal sodium intake no renal eects were ob-
served after either acute or repeated dosing. This was
despite the eective AT
1
receptor-blockade and mark-
edly elevated endogenous Ang II levels in the presence of
unopposed renal AT
2
receptors, especially on day 8.
Valsartan was well tolerated by healthy subjects at a
daily dose of 200 mg, with a similar frequency and
quality of AEs on active and placebo treatments. Head-
ache was the most frequent AE, a typical observation in
phase I studies where subjects are usually withdrawn
from caeine consumption. In a general population with
a low to moderate caeine consumption, acute caeine
withdrawal causes moderate to severe headache in up to
50% of subjects [32]. A relationship between caeine
withdrawal and headache in the present study is sup-
ported by the observation that headache occurred almost
exclusively on the days on which caeine consumption
was restricted (days 1 and 8).
In summary, it may be concluded that the pharma-
cokinetics of valsartan are unchanged at steady state,
with little expected accumulation in plasma after once-
daily administration of doses up to 200 mg. An acute
dose of 200 mg valsartan produces no eect on BP and
HR of supine healthy subjects with a normal sodium
intake. A small but statistically signi®cant decrease of
supine SBP and DBP from placebo is, however, detect-
able after 8 days of treatment. Upon passive tilting, the
increase in DBP normally reinforced by acute RAS
stimulation is blunted by treatment with valsartan,
suggesting that AT
1
receptor-blockade might be detect-
ed indirectly after a single dose of the drug. The rise in
plasma Ang II follows AT
1
blockade after a single dose,
but is more pronounced at steady state, probably due to
the concomitant decrease in blood pressure. Valsartan is
well tolerated and devoid of eects on water, electrolyte
and uric acid excretion at 200 mg per day in healthy
normotensive volunteers with a normal sodium intake.
Acknowledgements The authors would like to thank Mrs. M.
Waldmeier and Mrs. F. Connault for clinical assistance, Mrs. F.
Hell for the measurement of drug plasma and urine concentrations,
and Mrs. L. Hartmann, Mrs. M. Lartigot and Mr. H.P. Baum for
the angiotensin II determinations.
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