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Korean Journal of Urology
ⒸThe Korean Urological Association, 2010 647 Korean J Urol 2010;51:647-652
www.kjurology. org
DOI:10.4111/kju.2010.51.9.647
Sexual Dysfunction
Efficacy and Safety of Tadalafil 5 mg Administered Once Daily in
Korean Men with Erectile Dysfunction: A Prospective, Multicenter
Study
Dong Hyuk Kang, Joo Yong Lee, Sung Yul Park, Hong Sang Moon, Tae Yoong Jeong1, Tag Keun Yoo2,
Hong Yong Choi, Hae Young Park, Tchun Yong Lee, Seung Wook Lee2
Department of Urology, Hanyang University College of Medicine, Seoul, 1Myongji Hospital, Kwandong University College of Medicine,
Goyang, 2Eulji Hospital, Eulji University College of Medicine, Seoul, Korea
Purpose: The ai m of th is stu dy was to evalua te the effic acy of a daily dose of t adala fil
5 mg as well as its safety for the cardiovascular system in men with erectile dysfunction.
Materials and Methods: This study included a total of 162 men who were administered
a daily dose of tadalafil 5 mg between April and December of 2009. A total of 127 men
completed the 8-week clinical trial. The International Index of Erectile Function
(IIEF)-5, blood pressure, and heart rate were measured before treatment with tadalafil
(V1) and 4 (V2) and 8 weeks (V3) after treatment with tadalafil. Adverse effects were
assessed at V1, V2, and V3. In cases in which the International Prostate Symptom Score
(IPSS) was ≥8 at V1, maximal flow rate (Qmax) and postvoid residual volume (PVR)
were measured.
Results: The IIEF-5 values were 11.25±3.18, 14.56±3.79, and 16.91±3.56 at V1, V2, and
V3, respectively, with significant improvement (V1 vs. V2, p＜0.001; V1 vs. V3, p
＜0.001). The IPSS values were 10.59±5.56, 9.07±6.06, and 8.15±6.10 at V1, V2, and
V3, respectively, and the differences were statistically significant (V1 vs. V2, p＜0.001;
V1 vs. V3, p＜0.001). There were no significant differences in blood pressure or heart
rate. Adverse effects were observed in 7 men (5.51%) at V2 and in 5 men (3.94%) at V3.
Conclusions: Tadalafil 5 mg administered once-a-day may be effective in improving
erectile function. Adverse effects on the cardiovascular system may be minimal. In addi-
tion, it is believed that this may also be effective in improving voiding symptoms.
Key Words: Erectile dysfunction; Safety; Tadalafil; Treatment outcome
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial
License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Article History:
received
12 July, 2010
accepted
17 August, 2010
Corresponding Author:
Seung Wook Lee
Department of Urology, Eulji Hospital,
Eulji University College of Medicine, 14,
Hangeulbiseok-gil, Nowon-gu, Seoul
139-711, Korea
TEL: +82-2-970-8306
FAX: +82-2-970-8349
E-mail: swleepark@gm ail.com
INTRODUCTION
Erectile dysfunction (ED) is defined as insufficient erection
or inability to maintain erection for satisfactory sexual
intercourse. ED is caused by a combination of factors such
as physiologic, neurologic, hormonal, arterial, and cav-
ernosal impairments [1]. ED affects about 150 million men
worldwide, and the number of subjects who suffer from ED
is expected to double by 2025 as the result of improved life
expectancy and the age-related nature of ED [2]. The phos-
phodiesterase type-5 inhibitors (PDE5i) used worldwide
are sildenafil, vardenafil HCl, and tadalafil, which have
been used to treat about 40 million patients with ED [3].
Tadalafil is an oral selective PDE5 inhibitor that improves
erectile function by provoking sexual stimulation through
the nitric oxide (NO)-cyclic guanosine monophosphate
(cGMP) pathway [4]. It has a longer half-life than other
drugs, and its duration of action is 36 hours. Many studies
have demonstrated that once-a-day treatment with low-
dose tadalafil is efficacious and safe. Daily treatment with
low-dose PDE5i has clinical implications because it en-
ables healthy men to have sexual intercourse at any time
Korean J Urol 2010;51:647-652
648 Kang et al
without taking the drug immediately before each inter-
course attempt. After administration of tadalafil in a dose
of 5 mg daily, tadalafil reaches a stable serum concentration
within 5 days, and because this drug has the longest half-
life among the PDE5i drugs, it is the most suitable for once-
a-day treatment [5]. Recently, there was evidence that
PDE5i improve lower urinary tract symptoms (LUTS).
However, there have been few studies of once-a-day treat-
ment with low-dose tadalafil in Korea. Therefore, this
study was conducted to evaluate the efficacy, safety, and
improvement in ED and LUTS after once-a-day treatment
with tadalafil 5 mg.
MATERIALS AND METHODS
1. Subjects and st udy design
A total of 162 men with ED were enrolled between April and
December of 2009. Of the 162 patients, 127 completed the
8-week clinical trial. This study was an open, prospective,
noncomparative study conducted in three centers of urol-
ogy in Korea and approved by the Institutional Review
Board. All subjects were assessed by using the 5-item ver-
sion of the International Index of Erectile Function
(IIEF)-5, and those who had an IIEF-5 score of ＜18 were
selected for the study. Subjects with ED were classified into
4 groups according to the cutoff value reported by Ahn et
al [6 ]: tho se with no ED (II EF-5 s core≥18), mild ED (14≤
IIEF-5 score＜18), moderate ED (10≤IIEF-5 score＜14),
and severe ED (IIEF-5 score＜10). The following subjects
were included in the study: those who (1) were between 40
and 70 years old, (2) had an IIEF-5 score ＜18 on screening,
and (3) had a willingness and the ability to participate in
this clinical study. The following subjects were excluded
from the study: those who (1) had shown hypersensitivity
reactions to PDE5i, (2) were on medication with drugs af-
fecting erectile function such as 5-alpha-reductase in-
hibitor within 1 month, (3) had been diagnosed with ED and
had undergone surgery, and (4) were on medication with
nitrate preparations and NO providers. Before the start of
the study (V1), information on the duration of illness,
smoking and drinking status, and past medical history was
collected. In addition, a physical examination including the
measurement of blood pressure (BP) and heart rate (HR),
12-lead electrocardiography, routine laboratory tests, and
urinalysis was performed. All subjects were given tadalafil
(CialisⓇ) orally in a dose of 5 mg once-a-day immediately
after breakfast. They were asked to not take the drug more
than once daily. Its efficacy and safety were assessed at 4
(V2) and 8 weeks (V3) after the initial administration of the
drug. In 91 men (71.65%) with an International Prostate
Symptom Score (IPSS) of ≥8 at V1, the IPSS, maximal flow
rate (Qmax), and postvoid residual volume (PVR) as well
as the IIEF-5 were measured at V1, V2, and V3.
2. A sses s ment of efficacy and safet y
The efficacy of tadalafil 5 mg once-a-day was assessed by
using the IIEF-5 and Global Assessment Question (GAQ).
The IIEF-5 is a self-administered questionnaire that con-
sists of 5 domains assessing erectile function and inter-
course satisfaction. Higher scores in each domain reflect
better sexual function. The assessment of the efficacy of ta-
dalafil was supplemented by the dichotomous question
(GAQ), “Has the treatment you have taken over the past
8 weeks improved your erections?” For evaluation of the ef-
fects of tadalafil for LUTS, we measured the IPSS in all sub-
jects and LUTS were assessed only in subjects who had an
IPSS of ≥8 (n=91). In these subjects, Qmax and PVR to-
gether with the IIEF-5 score were assessed at V1, V2, and
V3. The subjects were further divided into 2 subgroups
[those with Qmax≥12 ml/sec (n=61, 67.03%) and those
with Qmax＜12 ml/sec (n=30, 32.97%)], and the efficacy
and safety of tadalafil were assessed for each. Safety evalu-
ation included history taking, physical examination, and
recording of adverse effects. The association of adverse ef-
fects with tadalafil was determined by the principal
investigator.
3. Statistical analysis
The intercourse satisfaction of the subjects was divided in-
to 4 categories: very satisfied, somewhat satisfied, some-
what dissatisfied, and very dissatisfied. “Being very sat-
isfied” and “being somewhat satisfied” were regarded as in-
tercourse satisfaction. Statistical comparisons of IPSS,
Qmax, and PVR before and after the use of tadalafil were
made with the paired t-test. Statistical analyses were per-
formed by using Open Office.org Calc (Open Office.orgⓇ
version 3.2.0, Oracle Corp, Redwood Shores, CA, USA) and
MedCalc (MedCalcⓇ version 11.2.1.0, MedCalc Software,
Mariakerke, Belgium). A p-value of ＜0.05 was considered
statistically significant.
RESULTS
The mean age of the subjects was 55.88±6.35 years, and the
duration of ED was 7.84±3.75 months. The subjects’ mean
body mass index (BMI) was 25.32±3.38 kg/m2, and their
mean abdominal circumference was 87.50±5.31 cm. The
causes of ED were as follows: psychogenic etiologies in 13
men (10.24%), organic etiologies in 50 (39.37%), mixed eti-
ologies in 37 (29.13%), and unknown etiologies in 27 (21.26%).
The subjects with organic etiologies were classified into
small groups according to guidelines [7]. The organic etiol-
ogies were as follows: vascular ED in 22 (17.32%), neuro-
genic in 9 (7.09%), anatomical or structural in 5 (3.94%),
hormonal in 4 (3.15%), and drug-induced in 10 (7.87%). The
concurrent diseases were as follows: hypertension in 36
men (28.35%), diabetes mellitus (DM) in 41 (32.28%), be-
nign prostatic hyperplasia (BPH) in 33 (25.98%), chronic
obstructive pulmonary disease (COPD) in 10 (7.87%), ten-
sion headache in 2 (1.57%), ischemic stroke in 2 (1.57%),
and major depression disorder in 2 (1.57%) (Table 1). In se-
verity, 35 men (27.56%) had mild disease, 52 (40.94%) had
moderate, and 40 (31.5%) had severe. At V2, 21 men (12.96%)
and at V3, 14 men (9.93%) dropped out of the study. Table 2
Korean J Urol 2010;51:647-652
Efficacy and Safety of Tadalafil 5 mg Once-A-Day 649
TABLE 1. Patient characteristics at baseline
Characteristics
No. of patients 127
A
ge (years) 55.88±6.35
BMI (kg/m2) 25.32±3.38
Duration of erectile dysfunction (months) 7.84±3.75
Etiology of erectile dysfunction
Psychogenic (%) 13 (10.24)
Organic (%) 50 (39.37)
Mixed (%) 37 (29.13)
Unknown (%) 27 (21.26)
Underlying disease
Hypertension (%) 36 (28.35)
DM (%) 41 (32.28)
BPH (%) 33 (25.98)
COPD (%) 10 (7.87)
Tension headache (%) 2 (1.57)
Ischemic stroke (%) 2 (1.57)
Major depression disorder (%) 2 (1.57)
BMI: body mass index, DM: diabetes mellitus, BPH: benign pro-
static hyperplasia, COPD: chronic obstructive pulmonary diseas
e
TABLE 2. Reasons for drug discontinuation
No. of patients (%)
Total (%)
V2 V3
Patients completed 141 (82.04) 127 (78.40) 127 (78.40)
Patients discontinued 21 (12.96) 14 (8.64) 35 (21.60)
Insufficient response 7 (4.32) 5 (3.09) 12 (7.41)
Not returning for 11 (6.79) 7 (4.32) 18 (11.11)
follow-up
Uncontrollable 3 (1.85) 2 (1.23) 5 (3.08)
response
V
2: 4 weeks, V3: 8 weeks
TABLE 3. Result of IIEF-5, IPSS, Qmax, and PVR
V1 V2 V3 p-value
IIEF-5 11.25±3.18 14.56±3.79 16.91±3.56 ＜0.001a
＜0.001b
Qmax (ml/s) (IPSS≥8, n=91) 13.85±4.38 13.97±4.41 14.04±4.40 0.124a
0.091b
Qmax (ml/s) (＜12 ml/sec, n=30) 8.46±1.51 8.61±1.87 8.87±2.06 0.218a
0.034b
Qmax (ml/s) (≥12 ml/sec, n=61) 16.34±2.68 16.43±2.74 16.41±2.89 0.304a
0.559b
PVR (ml) (IPSS≥8, n=91) 49.33±23.81 49.25±23.89 49.12±23.90 0.206a
0.052b
PVR (ml) (Qmax＜12 ml/sec, n=30) 48.26±24.49 48.31±24.60 47.75±24.26 0.685a
0.024b
PVR (ml) (Qmax≥12 ml/sec, n=61) 49.83±23.62 49.68±23.68 49.76±23.84 0.55a
0.547b
IIEF-5: International Index of Erectile Function-5, IPSS: International Prostate Symptom Score, Qmax: maximal flow rate, PVR:
post-void residual volume, V2: 4 weeks, V3: 8 weeks, a: V1 vs. V2, b: V1 vs. V3
shows the reasons for dropout.
The mean IIEF-5 score showed significant improvements
(Table 3). Regarding questions, the scores for all questions
were significantly higher (Fig. 1). At V1 with IPSS≥8, Qmax
and PVR were not significantly different. Only the IPSS
showed a significant difference between the groups. But,
in subjects with Qmax＜12 ml/sec, Qmax was improved sig-
nificantly at V3. PVR was also improved significantly at
V3. Otherwise, in subjects with Qmax≥12 ml/sec, Qmax
and PVR were not improved significantly (Table 3). There
were significant differences in Qmax (Fig. 2) and PVR be-
tween the 2 subgroups.
On the GAQ, 84 men (66.14%) reported “yes” at V2, and
95 men (74.80%) reported “yes” at V3. In intercourse sat-
isfaction after the endpoint of tadalafil administration, 59
men (46.46%) were “very satisfied,” 33 (25.98%) were
“somewhat satisfied,” 26 (20.47%) were “somewhat dissat-
isfied,” and 9 (7.09%) were “very dissatisfied.” Intercourse
satisfaction was observed in 92 men (72.44%), whereas 35
men expressed dissatisfaction by reason of ineffectiveness
(n=24, 68.57%), financial problems (n=5, 14.29%), and over
effect (n=6, 17.14%). A total of 74 men (58.27%) thought
that they could maintain normal erection during sexual
intercourse.
Adverse effects were observed in 7 men (5.51%) at V2 and
in 5 men (93.94%) at V3. Facial flushing was the most com-
mon adverse effect (n=3, 2.36% at V2; n=2, 1.57% at V3),
followed by headache (n=2, 1.57% each at V2 and V3), and
dizziness (n=2, 1.57% at V2; n=1, 0.79% at V3) (Table 4).
No subjects dropped out of the study as the result of adverse
effects.
The mean standing systolic BP was 126.95±7.18 mmHg
at V1, 127.55±7.87 mmHg at V2, and 127.28±7.83 mmHg
at V3 (V1 vs. V2, p=0.118; V1 vs. V3, p=0.396). The mean
standing diastolic BP was 82.12±4.00 mmHg at V1,
82.28±4.89 mmHg at V2, and 81.65±4.54 mmHg at V3 (V1
vs. V2, p=0.535; V1 vs. V3, p=0.087). The mean sitting sys-
Korean J Urol 2010;51:647-652
650 Kang et al
TABLE 4. Adverse effects 4 and 8 weeks after tadalafil treatmen
t
Adverse effects
No. of patients (%)
V2 V3
Cardiovascular disorders 3 (2.36) 2 (1.57)
Facial flushing 3 (2.36) 2 (1.57)
Nervous system disorders 4 (3.15) 3 (2.36)
Dizziness 2 (1.57) 1 (0.79)
Headache 2 (1.57) 2 (1.57)
Patients with at least 1 7 (5.51) 5 (3.94)
adverse effect
V
2: 4 weeks, V3: 8 weeks
FIG. 1. There was a significant domain score increase in all ques-
tions (Q1 to Q5) of the International Index of Erectile Function
(IIEF)-5.
FIG. 2. In the group with maximal flow rate (Qmax) less than 12
ml/sec (n=30, 32.97%), there was a significant increase in Qmax
compared with that in the group with Qmax of 12 or more than
12 ml/sec (n=61, 67.03%).
tolic BP was 121.33±8.49 mmHg at V1, 121.82±7.76 mmHg
at V2, and 120.17±6.38 mmHg at V3 (V1 vs. V2, p=0.111;
V1 vs. V3, p=0.118). The mean sitting diastolic BP was
77.22±5.52 mmHg at V1, 77.28±4.86 mmHg at V2, and
77.13±5.19 mmHg at V3 (V1 vs. V2, p =0.890; V1 vs. V3,
p=0.855). The mean standing HR was 76.28±5.38 at V1,
76.48±7.12 at V2, and 75.94±5.22 at V3 (V1 vs. V2, p=0.676;
V1 vs. V3, p=0.073). The mean sitting HR was 76.25±5.51
at V1, 76.21±5.44 at V2, and 76.19±5.43 at V3 (V1 vs. V2,
p=0.740; V1 vs. V3, p=0.697). None of the differences in car-
diovascular system variables were statistically significant.
DISCUSSION
ED was reported to affect 18 million men in the United
States and 189 million men globally in 2004, 193 million
men in 2005, and 198 million men in 2006 [8,9]. ED is re-
lated to chronic conditions such as atherosclerosis, dia-
betes mellitus, and obesity that reduce arterial blood flow.
Endothelial dysfunction caused by such conditions is con-
sidered to be an important factor for ED [10,11].
PDE5i suppress the degradation of cGMP in the smooth
muscle cells of the corpus spongiosum, which maintains
the relaxation of the smooth muscle cells induced by NO
or nitrate [12]. After the introduction of sildenafil citrate
(ViagraⓇ, Pfizer Inc, New York, NY, USA) in 1998, more
than 30 million men with ED have taken these drugs [13].
Thereafter, vardenafil HCI (LevitraⓇ, Ganyer-GSK, Ratitan,
NJ, USA), tadalafil (CialisⓇ, Lilly-ICOS, Indianapolis, IN,
USA), udenafil (ZydenaⓇ, Dang-A Pharmaceutial Company,
Seoul, Korea), and mirodenafil (MvixⓇ, SK Chemical, Seoul,
Korea) have been developed, with a high efficacy, a low inci-
dence of adverse effects, rapid onset of action, a longer dura-
tion of action, and a high specificity for PDE5 [14-17]. PDE5i
are currently first-line drugs for ED because of their high
efficacy, safety, and ease of use. Wespes et al have recom-
mended that men with ED should select the most effective
drug for themselves after the use of all available PDE5i
[18].
Previous studies have demonstrated that tadalafil im-
proves sexual functioning, intercourse satisfaction, and
quality of life for men and their female partners [19-21].
Tadalafil administered once-a-day eliminates the con-
ception that the use of this drug is limited to the sexual act
itself and instead improves sexual quality of life, unlike
on-demand products. Eardley et al reported that most men
have sexual intercourse within 30 minutes of their at-
tempt, regardless of the presence or absence of ED [22].
Fisher et al reported in a FEMALES study that 30% of men
and 34% of women do not perform a sexual act at a fixed
time [23]. These results suggest that sexual acts are not
performed at an expected time or during a fixed time period
and that there is a limitation in the use of PDE5i. The theo-
retical evidence for tadalafil administered once-a-day is
that desire for sexual intercourse is unexpected and sexual
intercourse is usually performed within a short period after
the decision.
Althof et al indicated that once-a-day treatment with ta-
dalafil 5 mg improves erection, vaginal penetration, and
overall sexual satisfaction compared with that in a placebo
Korean J Urol 2010;51:647-652
Efficacy and Safety of Tadalafil 5 mg Once-A-Day 651
group and that in both men with ED and their female part-
ners, erection achievement (99.0% and 96.6%, respectively),
vaginal penetration (98.6% and 97.4%, respectively), and
overall intercourse satisfaction (84.3% and 82.8%, respec-
tively) were excellent compared with the placebo group [24].
McVary et al stated that the IIEF-EF domain score and
IPSS were significantly higher 6 and 12 weeks after once-a-
day treatment with tadalafil 5 mg in the treatment group
than in the placebo group [25]. In our study, IIEF-5 scores
for all items were significantly increased after once-a-day
treatment with tadalafil 5 mg. As for intercourse satisfac-
tion, most men reported had intercourse satisfaction after
the use of tadalafil. Roehrborn et al reported that LUTS se-
condary to BPH were improved 4, 8, and 12 weeks after the
once-a-day administration of tadalafil 5 mg in the treat-
ment group as compared with the placebo group and that
there were no significant differences in Qmax between the
treatment and placebo groups [26]. Similarly, the IPSS was
significantly improved in this study, but Qmax and PVR
were not. However, in men with Qmax＜12 ml/sec, Qmax
and PVR were improved. Kaplan and Hatzichristou said,
“It is reasonable to assume that the reason why Qmax did
not improve is because flow rate was normal at baseline
[27]. There were no upper limits or exclusion criteria based
on flow rate and consequently, how can one expect to im-
prove a ‘normal’ flowrate?” So we think this was a very
meaningful study because there are no reports based on low
Qmax patients.
Because PDE5 exists in the vessels, bronchus, esoph-
agus, anal sphincter, urethra, and prostate, tadalafil caus-
es adverse effects in these organs. Seftel et al reported that
the most common treatment-emergent adverse events
were headache (15.7% vs. 6.3% with placebo), back pain
(8.8% vs. 0%), and dyspepsia (7.5% vs. 0%) after on-demand
20 mg tadalafil administration during 12 weeks [28].
Roehrborn et al documented that most men with ED toler-
ate a wide range of doses, so they can take the drug con-
tinually, and that there were no significant differences in
tadalafil-associated adverse effects between the treatment
and placebo groups [26].
Our study is subject to some limitations. First, there
were no placebo and control groups comparable to each
other. Second, this study had a limitation stemming from
a relatively short follow-up period (8 weeks). Third, we did
not restrict the use of alpha-blocker medication; therefore,
the results concerning LUTS cannot be regarded as a pure
effect of tadalafil. However, to the best of our knowledge,
this is the first such study in Korea. Further studies with
a larger sample size and a longer follow-up period are need-
ed to confirm our results.
CONCLUSIONS
There were a few mild adverse effects in men with ED taken
tadalafil 5 mg once-a-day. This treatment improved sexual
functioning, overall intercourse satisfaction, and LUTS.
The results of this study suggest that tadalafil 5 mg ad-
ministered once-a-day may be effective in the treatment of
ED with acceptable tolerability.
Conflicts of Interest
The authors have nothing to disclose.
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