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- Review -
More than eight years' hands-on experience with the novel long-acting parenteral testosterone undecanoate
Farid Saad1,2, Axel
Kamischke3, Aksam Yassin2,4, Michael
Zitzmann3, Markus Schubert5, Friedrich
Jockenhövel6, Hermann M.
Behre7, Louis Gooren8, Eberhard
Nieschlag3
1Bayer-Schering, Department of Men's Health, Berlin, Germany
2Gulf Medical College School of Medicine, Ajman, United Arab Emirates
3Institute of Reproductive Medicine of the University of Munster, Munster, Germany
4Department of Urology, Segeberger Kliniken, Norderstedt, Germany
5Innere Medizin, Klinikum der Universität zu Köln, Köln, Germany
6Evangelisches Krankenhaus Herne, Herne, Germany
7Andrology Unit, Department of Urology, Martin-Luther University, Halle, Germany
8Department of Endocrinology, Andrology Section, Vrije Universiteit Medical Center, Amsterdam, the Netherlands
Abstract
Testosterone (T) as a compound for treatment of T deficiency has been available for almost 70 years, but the
pharmaceutical formulations have been less than ideal. Traditionally, injectable T esters have been used for treatment,
but they generate supranormal T levels shortly after the 2-3 weekly injection interval. T levels then decline very
rapidly, becoming subnormal during the days preceding the next injection. The rapid fluctuations in plasma T are
subjectively experienced as disagreeable. T undecanoate (TU) is a new injectable T preparation with a considerably
better pharmacokinetic profile. After two initial injections separated by a 6-week interval, the following intervals
between two injections are generally 12 weeks, eventually amounting to a total of four injections per year. Plasma T
levels with this preparation are nearly always in the range of normal men, as are its metabolic products estradiol and
dihydrotestosterone (DHT). It reverses the effects of hypogonadism on bone and muscle and metabolic parameters,
and on sex functions. It is suitable for male contraception. Its safety profile is excellent because of the continuous
normalcy of plasma T levels. No polycythemia has been observed and no adverse effects on lipid profiles. Prostate
safety parameters are well within reference limits. TU is a valuable treatment option of androgen
deficiency. (Asian J Androl 2007 May; 9: 291_297)
Keywords: testosterone treatment; testosterone undecanoate; pharmacokinetic profile; clinical efficacy; side effects; sexual dysfunction;
male contraception
Correspondence to: Dr Farid Saad, Bayer-Schering Pharma, Men's Healthcare, 13342 Berlin, Germany.
Tel: +49-30-4681-5057 Fax: +49-30-4689-5057
E-mail: Farid.Saad@bayerhealthcare.com
Received 2007-01-30 Accepted 2007-02-08
DOI: 10.1111/j.1745-7262.2007.00275.x
1 Introduction
There are a number of new treatment modalities for
androgen deficiency, such as transdermal testosterone
(T) gels, a buccal T tablet, and injectable long-acting
T undecanoate (TU) in castor oil, which appears to be a real
depot preparation requiring only four injections per year [1,
2]. In this review the pharmacokinetics, the first clinical
experiences and the use of TU for the treatment of sexual
dysfunction and male contraception are summarized.
2 Pharmacokinetic studies
Injectable TU was first used in China for the
treatment of hypogonadism [3], and later also for
contraception [4, 5]. The long half-life of the Chinese preparation
was confirmed in monkeys [6] and in hypogonadal men
in Europe. In a study by Behre et al. [7] it was found
that TU dissolved in castor oil had better
pharmacokinetic properties than TU dissolved in tea-seed oil. TU
appeared to generate plasma T levels with longer
half-lives, and which did not exceed the upper limit of normal.
In an initial multiple-dose kinetics study, 13 hypogonadal
men received four intramuscular injections of TU (Nebido, Bayer-Schering Pharma, Berlin, Germany ) at
6-week intervals [8]. Serum T levels were never found
to lie below the lower limit of normal and, only briefly
after the 3rd and 4th injection, serum T levels were above
the upper limit of normal, while peak and trough levels
increased over the 24-week observation period with this
regimen of an injection every 6 weeks. Serum estradiol
and dihydrostestosterone (DHT) followed this pattern,
not exceeding the normal limits [8]. The same research
group performed a study to establish suitable injection
intervals for TU. In seven hypogonadal men, injections
were given at gradually increasing intervals between the
5th and 10th injection (starting with 6-week injection
intervals) and from then on every 12 weeks. Steady
state kinetics were assessed after the 13th injection.
Cmax was 32.0 ± 11.7 nmol/L and half-life was 70.2 ± 21.1
days. The mean Cmax of 32 nmol/L seen during
steady-state with TU administration was lower than that achieved
by transdermal T gel (Testogel, Besins-Iscovesco, Paris,
France) 100 mg/day (37.5 nmol/L). However, it was higher
than with transdermal T gel 50 mg/day (28.8 nmol/L) and
testosterone skin patch (Androderm, Watson Pharmaceuticals,
Corona, CA, USA) 5mg/day (26.5 nmol/L). Before the next
injection, the serum levels for T and its metabolites DHT
and estradiol were mostly within the normal (eugonadal)
range and showed a tendency to decrease with
increasing length of injection intervals. The study concluded
that after initial loading doses at 0 and 6 weeks, injection
intervals of 12 weeks establish eugonadal values of
serum T in almost all men [9].
Clinical long-term experience up to 120 weeks was
also published in 2004 by another group (Bueber V
et al. Treatment of hypogonadal men with long-acting
testosterone undecanoate (TU): Clinical and pharmacokinetic
results after intramuscular application of 1 000 mg TU
every three months up to 120 weeks. The Endocrine Society's 86th Annual Meeting, June 16_19, 2004,
p.445 [PS-556]). Twenty-six hypogonadal patients received
TU (1 000 mg/4mL) in a first-stage of the study in weeks
0, 6, 16, 26 and 36, followed by an additional stage of up
to 120 weeks with injections every 12 weeks. Supranormal
peak concentrations of total and free T occurred 2 weeks
after the first injection, then a decrease to within the
physiological range was observed. At the end of the study,
during the wash-out period, serum T levels declined to
the low pre-treatment levels 14 weeks after the final
injection. A parallel increase of 17β-estradiol levels was
seen, but the decrease to pre-treatment levels was sooner
than that of T and occurred by 4 weeks after the last
injection. Serum LH and FSH were suppressed during
the treatment period, while sex hormone binding
globulin (SHBG) remained stable. Serum prostate-specific
antigen (PSA) rose from 0.660 to 0.976 ng/mL (P
< 0.01) after 120 weeks, but did not exceed the normal range. Prostate
volume increased from 19.6 to 26 mL (P <
0.05). Osteocalcin rose from 0.734 to 1.049 nmol/L
(P < 0.01). Bone mineral density (BMD) did not change.
Standard laboratory tests and uroflow did not change. Sexual
interest (assessed by use of the Aging Male Symptoms
score [AMS] questionnaire) increased.
There is now long-term experience of more than 8
years with TU in 22 hypogonadal men [10].
Individual dosing intervals ranged from 10 to 14
weeks. Serum trough levels of T were generally above
the lower limit of normal, indicating sufficient
substitution over the previous injection interval. In contrast to
short-acting T esters, perceptions of fluctuations in
androgen serum concentrations were rare. If this was the
case, it occurred during the last 2 weeks before the next
injection, indicating that levels of T had fallen below
normal. Interestingly, patients recognize psychosomatic
symptoms when plasma T levels fall below an individual
threshold value [11]. Summarizing the two key studies
by Zitzmann and Nieschlag [12] and Schubert et
al. [13], the following regimen of administration is recommended
for TU therapy in hypogonadal men: the second injection
of 1 000 mg TU should be administered 6 weeks after
the first injection of 1 000 mg TU (loading dose),
followed by injections every 12 weeks. An individualisation
of the TU therapy should be recommended. If the T
serum concentration before the 4th injection lies between
10_15 nmol/L, then the injection interval should be
maintained every 12 weeks. If the T serum concentration at
this time is lower than 10 nmol/L, then the injection
interval should be shortened to 10 weeks. If the T level is,
however, greater than 15 nmol/L, then the injection
interval can be extended to 14 weeks. Additionally,
clinical symptoms carry weight for the individualisation of
injection intervals with TU therapy [11]. The loading
dose of TU achieved by the first two injections with an
interval of 6 weeks is also recommended for patients
who are being transferred from short-acting T
injections (e.g. T enanthate [TE] 250 mg) to treatment with
TU.
3 Therapy of hypogonadism with TU
The efficacy of TU has been compared to the
previous standard therapy of 250 mg TE i.m. administered
every three weeks in a 30-week controlled, prospective,
randomized, parallel-group study [13]. During the first
30 weeks of the comparative phase, 40 hypogonadal men
with T levels below 5 nmol/L were randomly assigned to
either 250 mg TE i.m. every 3 weeks (n = 20) or TU
three times at 6-week intervals followed by a 9-week
interval. Following the first 30 weeks of the
comparative part of the study, all patients received TU every 12
weeks in the one-arm follow-up study over an additional
30 months. During the first 30 weeks there were no
differences in sexual parameters (spontaneous morning
erections, total erections, ejaculations) between the two
groups. After 30 weeks, serum PSA levels in both
treatment groups had risen slightly, but remained stable
during long-term TU administration and stayed within the
normal range over the entire observation period.
Prostate volumes increased during the first 30 weeks to a
similar degree with both T preparations but then remained
stable until the end of the follow-up study [13].
Comparing the mean baseline levels with the mean levels after
follow-up, there was an increase of serum T (from 3.9
to 16.2 nmol/L), of PSA serum levels (from 0.27 to 0.75
ng/mL) and of prostate volume (from 14.5 to 20.2 mL),
whereas a decline of serum total cholesterol (from 235.3
to 202.4 mg/dL), low-density lipoprotein (LDL)
cholesterol ( from 158.8 to 134.9 mg/dL), high-density
lipoprotein (HDL) cholesterol (from 46.1 to 42.8 mg/dL)
and triglycerides (from 199.9 to 161.2 mg/dL) was observed. Using a standardized self-evaluation
questionnaire for assessing psychosexual effects of TU treatment,
it was found that scores for sexual thoughts/fantasies
and sexual interest/desire doubled. The score for
satisfaction of sex life also increased. Improvements were
seen for waking erections, total number of erections, and
number of ejaculations. The psychological parameters
for depression, fatigue and anxiety decreased within the
first 3-6 weeks and remained stable thereafter. There
were no statistically significant differences between TE
and TU. No significant change was observed in the score
for aggressiveness in either group, indicating that this
parameter was not affected by the treatment provided.
These results obtained in hypogonadal men are paralleled
in some respects by the study of O'Connor et
al. [14] showing that a single injection of 1 000 mg TU to 28
eugonadal young men, elevating mean T levels above
normal, was associated with significant increases in
anger-hostility from baseline to week 2 after the injection.
It was accompanied by an overall reduction in
fatigueinertia, and did not increase aggressive behaviour or induce any
changes in non-aggressive or sexual behaviour.
It is now clear that TU is at least as effective and
safe as the standard injectable formulation and requires
only four injections per year in long-term treatment while
maintaining serum T levels within the physiological range.
There are data to confirm the safety and efficacy of
long-term TU therapy of hypogonadal patients treated over a
period of more than 8 years [15]. The study included 22
patients who received TU up to 8.5 years at injection
intervals of approximately 12 weeks. Patients reported
restoration of sexual functions and positive changes in
mood patterns. In contrast to short-acting TE preparations,
patients rarely reported perceptions of fluctuations in
androgen concentrations. Over the whole treatment period,
PSA concentrations did not exceed the normal range and
prostate size remained below 30 mL in all patients.
Haemoglobin and hematocrit increased initially during
treatment but remained within the normal range over the
entire treatment period. Computer tomography of the
lumbar spine showed that bone density improved in all
patients during the first 2 years and remained stable
thereafter. Body mass index (BMI) decreased during
the first 2 years of treatment. Serum total cholesterol
levels did not change over the treatment period and
serum LDL levels decreased slightly, parallel to the decrease
of BMI, and serum HDL levels increased slightly over
time. There were no relevant changes in blood pressure
or heart rate. Overall, treatment with intramuscular TU
appeared to have beneficial effects on body
composition and lipid profile (Zitzmann M, von Eckardstein S,
Saad F, Nieschlag E. Long-term experience with
injections of testosterone undecanoate for substitution
therapy in hypogonadal men. In: 87th Annual Meeting
of the Endocrine Society; 2005 June 4_7; San Diego,
CA; p. 306).
The above studies were confirmed recently by a study in elderly men (Jacobeit JW, Schulte HM.
Long-acting intramuscular testosterone undecanoate [TU,
NebidoÒ] in treatment of aging males with hypogonadism.
8th European Congress of Endocrinology, Glasgow,
1_5 April 2006, Poster No. P184).
Thirty-three hypogonadal men with primary,
secondary or late-onset hypogonadism, between the ages of
45_79 years, were treated with TU. Serum T levels increased
from 9.0 ± 3.8 nmol/L at baseline to 13.5 ± 4.6 nmol/L
after 6 weeks and to 16.4 ± 6.4 nmol/L after 30 weeks
of treatment. DHT levels increased from 0.98 ± 0.48
nmol/L to 3.1 ± 1.0 nmol/L. Serum PSA levels
fluctuated minimally in the normal range. In two patients, the
length between two injections could be prolonged from
12 to 14 weeks. All patients reported improved mood,
sexual function and quality of life.
4 Treatment of erectile dysfunction (ED) with TU
There is a renewed interest in the treatment of
erectile dysfunction (ED) with T. Apart from its well-known
effects on libido, T appears to have significant direct
effects on anatomical and physiological properties of
erectile tissue [16, 17], and there are some interesting new
observations. In support of a direct effect of T on penile
tissues, treatment with TU appeared to improve
veno-occlusive dysfunction evidenced by cavernosographic
changes in hypogonadal patients with severe ED,
diabetes mellitus, obesity and/or metabolic syndrome who had
earlier not responded to PDE5 inhibitors and alprostadil
injections [18, 19]. One patient having venous leakage
prior to T administration received treatment with TU at
12_14 week intervals following a loading dose of 6 weeks.
The patient showed improved sexual function after 9
weeks of treatment and repeated cavernosography after
12 weeks revealed that the venous leakage had receded
[18]. The results from this case study suggest that TU
has a positive impact on the veno-occlusive properties
of penile trabecular tissues in hypogonadal ED patients.
This finding has been replicated in five out of 12
hypogonadal patients [19]. These results confirm data
obtained from animal studies showing that androgen
insufficiency leads to veno-occlusive dysfunction, which
cannot be restored with PDE-5 inhibitor treatment alone
[20].
In a study assessing the impact of T therapy alone
on ED, 22 hypogonadal men with ED received injections
with TU, and sexual function was assessed using the
International Index of Erectile Function (IIEF). While in
all patients T therapy alone significantly improved the
sexual desire domain of the IIEF (from 4.5 to 8.4 on a
scale of 10), in 12 out of 22 patients (54%) the erectile
function domain score increased from 12 at baseline
(moderate ED) to 25 (indicating normal erectile function)
at week 24. It is of note that the effect of T on erectile
function may appear as late as 12-24 weeks of
administration of T [21]. These observations have been
extended to larger groups of patients confirming the
results of the above study, which have been submitted for
publication.
5 TU for male contraception
Exogenous administration of T functions as a
contraceptive in the male by suppressing the secretion of LH and
FSH from the pituitary. This approach to contraceptive
development appears safe and fully reversible; however,
sperm concentrations are not suppressed to zero in all
men. Therefore, researchers have combined T with progestins to further suppress pituitary
gonadotropins and optimize contraceptive efficacy [22_24]. Surprisingly,
studies in East Asian men show that intramuscular TU
alone affords better suppression of spermatogenesis and
protection against pregnancy than does male condom use,
and thus use of TU alone could suffice for contraceptive
use in East Asian men [25].
In contrast to East Asians, only approximately 60%
of Caucasian volunteers exhibited azoospermia
following treatment with TU alone administered every 6 weeks
[26]. However, these results with TU, which are
comparable to those obtained following weekly injections of
TE, offer the advantage of longer injection intervals, and
therefore TU is the most promising androgen preparation
for further development as a male contraceptive if
combined with potent progestins [22_24]. To increase
long-term acceptability of the regimen, TU injection intervals
might even be prolonged to 8 or 12 weeks. Meriggiola
et al. [27] showed that injections of TU every 8 weeks
combined with 200 mg of the long-acting parenteral
norethisterone enanthate (NETE) very effectively
suppressed spermatogenesis in normal men.
For many years, the lack of suitable T formulations
in terms of pharmacokinetics and of convenience of
administration has hampered the development of male
hormonal contraceptives. Recent studies using TU
represent a turning point in the development of male
hormonal contraceptives [22_24]. Despite the requirement
for regular injections, the acceptability of this regimen
(TU combined with NETE) is high [23, 27].
6 Safety and tolerability
TU is generally well tolerated. Local irritation at the
site of injection is moderate, does not last longer than
three days and can be minimised by administering TU
slowly over a period of at least 1 min. Very few patients
reported irritation or pain at the injection site despite the
large volume of injection of 4 mL. No patient
discontinued treatment as a result of problems of local discomfort.
TU should be injected deeply into the gluteal muscle. The
patient should be in a prone position. During the first
year of TU treatment, for safety reasons, erythropoiesis
parameters and prostate size and serum PSA should be
monitored in men above the age of 45 years at quarterly
intervals and then yearly thereafter [28].
Several treatment options exist for hypogonadal
patients; the most commonly used are injectable T esters
such as TE with injection intervals of 2_3 weeks. Their
administration is associated with supra-physiological peak
values shortly after the injection and to
sub-physiological levels in the days before the new injection. This
often leads to mood swings or emotional instability.
Another important consequence of the supra-physiological
T levels under treatment with TE is the induction of
elevations of the hematocrit [29]. Of 70 older men with
low serum T receiving 200 mg of TE every other week,
30% developed a hematocrit greater than 52% [30, 31].
In another study of 32 hypogonadal men receiving 200
mg TE every other week, 14 patients (43.8%) had at
least one occurrence of an elevated hematocrit value [32].
Elevated hematocrit values may lead to
thrombo-embolic events.
No major adverse effects were encountered in the
clinical trials of TU. This is not surprising as the
pharmaceutically active component is T itself. Common side
effects of T administration, such as gynecomastia, breast
tenderness and acne were reported in only a minority of
patients. This absence of side effects is probably to be
ascribed to the largely normal physiological levels of T,
and its derivatives DHT and estradiol, achieved with TU.
Adverse effects were observed in the initial studies when
the dosing schedule was not yet well established and the
higher frequency of administration of TU led to
higher-than-normal levels of T. Significant increase in PSA and
prostate size were noted in some of these trials; however,
this is a result of the fact that hypogonadal men have
subnormal PSA values and small prostate sizes at baseline
and the increase is observed with every treatment
modality of T administration upon normalization of plasma
T levels. In a systematic review, the average PSA
increase after initiation of T therapy was 0.3 ng/mL in
young hypogonadal men and 0.44 ng/mL in older men [33].
In the further course of treatment with TU, PSA
levels and prostate size remained stable and within the
normal range. Similarly, increases of parameters of
erythropoiesis to eugonadal values were observed, but there was
no occurrence of polycythemia as observed in studies
with the more traditional T esters [29, 31, 32]. Only one
study showed a transient decline in serum HDL cholesterol; however, its value remained within the
normal range. For a review see Harle et al. [2]. It is clear
now that TU is at least as effective and safe as the
standard injectable formulation and eventually requires only
four injections per year, while maintaining serum T
levels within the physiological range. There are data to
confirm the safety and efficacy of long-term TU therapy in
hypogonadal patients treated over a period of more than
8 years. TU appears to be a safe modality of T treatment,
because with the presently established dosage regimen,
plasma T levels remain in the physiological range.
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