Mechanism of Action
Animal studies have indicated the following mode of action. At the cellular
level, alendronate shows preferential localization to sites of bone resorption,
specifically under osteoclasts. The osteoclasts adhere normally to the bone
surface but lack the ruffled border that is indicative of active resorption.
Alendronate does not interfere with osteoclast recruitment or attachment, but
it does inhibit osteoclast activity. Studies in mice on the localization of
radioactive [3H]alendronate in bone showed about 10-fold higher uptake
on osteoclast surfaces than on osteoblast surfaces. Bones examined 6 and 49
days after [3H]alendronate administration in rats and mice, respectively,
showed that normal bone was formed on top of the alendronate, which was incorporated
inside the matrix. While incorporated in bone matrix, alendronate is not pharmacologically
active. Thus, alendronate must be continuously administered to suppress osteoclasts
on newly formed resorption surfaces. Histomorphometry in baboons and rats showed
that alendronate treatment reduces bone turnover (i.e., the number of sites
at which bone is remodeled). In addition, bone formation exceeds bone resorption
at these remodeling sites, leading to progressive gains in bone mass.
Pharmacokinetics
Absorption
Relative to an intravenous (IV) reference dose, the mean oral bioavailability
of alendronate in women was 0.64% for doses ranging from 5 to 70 mg when administered
after an overnight fast and two hours before a standardized breakfast. Oral
bioavailability of the 10 mg tablet in men (0.59%) was similar to that in women
when administered after an overnight fast and 2 hours before breakfast.
FOSAMAX 70 mg oral solution and FOSAMAX 70 mg tablet are equally bioavailable.
A study examining the effect of timing of a meal on the bioavailability of
alendronate was performed in 49 postmenopausal women. Bioavailability was decreased
(by approximately 40%) when 10 mg alendronate was administered either 0.5 or
1 hour before a standardized breakfast, when compared to dosing 2 hours before
eating. In studies of treatment and prevention of osteoporosis, alendronate
was effective when administered at least 30 minutes before breakfast.
Bioavailability was negligible whether alendronate was administered with or
up to two hours after a standardized breakfast. Concomitant administration of
alendronate with coffee or orange juice reduced bioavailability by approximately
60%.
Distribution
Preclinical studies (in male rats) show that alendronate transiently distributes to soft tissues following 1 mg/kg IV administration but is then rapidly redistributed to bone or excreted in the urine. The mean steady-state volume of distribution, exclusive of bone, is at least 28 L in humans. Concentrations of drug in plasma following therapeutic oral doses are too low (less than 5 ng/mL) for analytical detection. Protein binding in human plasma is approximately 78%.
Metabolism
There is no evidence that alendronate is metabolized in animals or humans.
Excretion
Following a single IV dose of [14C]alendronate, approximately 50%
of the radioactivity was excreted in the urine within 72 hours and little or
no radioactivity was recovered in the feces. Following a single 10 mg IV dose,
the renal clearance of alendronate was 71 mL/min (64, 78; 90% confidence interval
[CI]), and systemic clearance did not exceed 200 mL/min. Plasma concentrations
fell by more than 95% within 6 hours following IV administration. The terminal
half-life in humans is estimated to exceed 10 years, probably reflecting release
of alendronate from the skeleton. Based on the above, it is estimated that after
10 years of oral treatment with FOSAMAX (10 mg daily) the amount of alendronate
released daily from the skeleton is approximately 25% of that absorbed from
the gastrointestinal tract.
Special Populations
Pediatric: The oral bioavailability in children was similar to
that observed in adults; however, FOSAMAX is not indicated for use in children
(see PRECAUTIONS, Pediatric Use).
Gender: Bioavailability and the fraction of an IV dose excreted
in urine were similar in men and women.
Geriatric: Bioavailability and disposition (urinary excretion)
were similar in elderly and younger patients. No dosage adjustment is necessary
(see DOSAGE AND ADMINISTRATION).
Race: Pharmacokinetic differences due to race have not been studied.
Renal Insufficiency: Preclinical studies show that, in rats with
kidney failure, increasing amounts of drug are present in plasma, kidney, spleen,
and tibia. In healthy controls, drug that is not deposited in bone is rapidly
excreted in the urine. No evidence of saturation of bone uptake was found after
3 weeks dosing with cumulative IV doses of 35 mg/kg in young male rats. Although
no clinical information is available, it is likely that, as in animals, elimination
of alendronate via the kidney will be reduced in patients with impaired renal
function. Therefore, somewhat greater accumulation of alendronate in bone might
be expected in patients with impaired renal function.
No dosage adjustment is necessary for patients with mild-to-moderate renal
insufficiency (creatinine clearance 35 to 60 mL/min). FOSAMAX is not recommended
for patients with more severe renal insufficiency (creatinine clearance < 35
mL/min) due to lack of experience with alendronate in renal failure.
Hepatic Insufficiency: As there is evidence that alendronate
is not metabolized or excreted in the bile, no studies were conducted in patients
with hepatic insufficiency. No dosage adjustment is necessary.
Drug Interactions
(also see PRECAUTIONS: DRUG INTERACTIONS)
Intravenous ranitidine was shown to double the bioavailability of oral alendronate.
The clinical significance of this increased bioavailability and whether similar
increases will occur in patients given oral H2-antagonists is unknown.
In healthy subjects, oral prednisone (20 mg three times daily for five days)
did not produce a clinically meaningful change in the oral bioavailability of
alendronate (a mean increase ranging from 20 to 44%).
Products containing calcium and other multivalent cations are likely to interfere
with absorption of alendronate.
Pharmacodynamics
Alendronate is a bisphosphonate that binds to bone hydroxyapatite and specifically inhibits the activity of osteoclasts, the bone-resorbing cells. Alendronate reduces bone resorption with no direct effect on bone formation, although the latter process is ultimately reduced because bone resorption and formation are coupled during bone turnover.
Osteoporosis in postmenopausal women
Osteoporosis is characterized by low bone mass that leads to an increased risk
of fracture. The diagnosis can be confirmed by the finding of low bone mass,
evidence of fracture on x-ray, a history of osteoporotic fracture, or height
loss or kyphosis, indicative of vertebral (spinal) fracture. Osteoporosis occurs
in both males and females but is most common among women following the menopause,
when bone turnover increases and the rate of bone resorption exceeds that of
bone formation. These changes result in progressive bone loss and lead to osteoporosis
in a significant proportion of women over age 50. Fractures, usually of the
spine, hip, and wrist, are the common consequences. From age 50 to age 90, the
risk of hip fracture in white women increases 50-fold and the risk of vertebral
fracture 15- to 30-fold. It is estimated that approximately 40% of 50-year-old
women will sustain one or more osteoporosis-related fractures of the spine,
hip, or wrist during their remaining lifetimes. Hip fractures, in particular,
are associated with substantial morbidity, disability, and mortality.
Daily oral doses of alendronate (5, 20, and 40 mg for six weeks) in postmenopausal
women produced biochemical changes indicative of dose-dependent inhibition of
bone resorption, including decreases in urinary calcium and urinary markers
of bone collagen degradation (such as deoxypyridinoline and cross-linked N-telopeptides
of type I collagen). These biochemical changes tended to return toward baseline
values as early as 3 weeks following the discontinuation of therapy with alendronate
and did not differ from placebo after 7 months.
Long-term treatment of osteoporosis with FOSAMAX 10 mg/day (for up to five
years) reduced urinary excretion of markers of bone resorption, deoxypyridinoline
and cross-linked N-telopeptides of type l collagen, by approximately 50% and
70%, respectively, to reach levels similar to those seen in healthy premenopausal
women. Similar decreases were seen in patients in osteoporosis prevention studies
who received FOSAMAX 5 mg/day. The decrease in the rate of bone resorption indicated
by these markers was evident as early as one month and at three to six months
reached a plateau that was maintained for the entire duration of treatment with
FOSAMAX. In osteoporosis treatment studies FOSAMAX 10 mg/day decreased the markers
of bone formation, osteocalcin and bone specific alkaline phosphatase by approximately
50%, and total serum alkaline phosphatase by approximately 25 to 30% to reach
a plateau after 6 to 12 months. In osteoporosis prevention studies FOSAMAX 5
mg/day decreased osteocalcin and total serum alkaline phosphatase by approximately
40% and 15%, respectively. Similar reductions in the rate of bone turnover were
observed in postmenopausal women during one-year studies with once weekly FOSAMAX
70 mg for the treatment of osteoporosis and once weekly FOSAMAX 35 mg for the
prevention of osteoporosis. These data indicate that the rate of bone turnover
reached a new steady-state, despite the progressive increase in the total amount
of alendronate deposited within bone.
As a result of inhibition of bone resorption, asymptomatic reductions in serum
calcium and phosphate concentrations were also observed following treatment
with FOSAMAX. In the long-term studies, reductions from baseline in serum calcium
(approximately 2%) and phosphate (approximately 4 to 6%) were evident the first
month after the initiation of FOSAMAX 10 mg. No further decreases in serum calcium
were observed for the five-year duration of treatment; however, serum phosphate
returned toward prestudy levels during years three through five. Similar reductions
were observed with FOSAMAX 5 mg/day. In one-year studies with once weekly FOSAMAX
35 and 70 mg, similar reductions were observed at 6 and 12 months. The reduction
in serum phosphate may reflect not only the positive bone mineral balance due
to FOSAMAX but also a decrease in renal phosphate reabsorption.
Osteoporosis in men
Treatment of men with osteoporosis with FOSAMAX 10 mg/day for two years reduced urinary excretion of cross-linked N-telopeptides of type I collagen by approximately 60% and bone-specific alkaline phosphatase by approximately 40%. Similar reductions were observed in a one-year study in men with osteoporosis receiving once weekly FOSAMAX 70 mg.
Glucocorticoid-induced Osteoporosis
Sustained use of glucocorticoids is commonly associated with development of
osteoporosis and resulting fractures (especially vertebral, hip, and rib). It
occurs both in males and females of all ages. Osteoporosis occurs as a result
of inhibited bone formation and increased bone resorption resulting in net bone
loss. Alendronate decreases bone resorption without directly inhibiting bone
formation.
In clinical studies of up to two years' duration, FOSAMAX 5 and 10 mg/day reduced
cross-linked N-telopeptides of type I collagen (a marker of bone resorption)
by approximately 60% and reduced bone-specific alkaline phosphatase and total
serum alkaline phosphatase (markers of bone formation) by approximately 15 to
30% and 8 to 18%, respectively. As a result of inhibition of bone resorption,
FOSAMAX 5 and 10 mg/day induced asymptomatic decreases in serum calcium (approximately
1 to 2%) and serum phosphate (approximately 1 to 8%).
Paget's disease of bone
Paget's disease of bone is a chronic, focal skeletal disorder characterized by greatly increased and disorderly bone remodeling. Excessive osteoclastic bone resorption is followed by osteoblastic new bone formation, leading to the replacement of the normal bone architecture by disorganized, enlarged, and weakened bone structure.
Clinical manifestations of Paget's disease range from no symptoms to severe morbidity due to bone pain, bone deformity, pathological fractures, and neurological and other complications. Serum alkaline phosphatase, the most frequently used biochemical index of disease activity, provides an objective measure of disease severity and response to therapy.
FOSAMAX decreases the rate of bone resorption directly, which leads to an indirect decrease in bone formation. In clinical trials, FOSAMAX 40 mg once daily for six months produced significant decreases in serum alkaline phosphatase as well as in urinary markers of bone collagen degradation. As a result of the inhibition of bone resorption, FOSAMAX induced generally mild, transient, and asymptomatic decreases in serum calcium and phosphate.
Clinical Studies
Treatment of osteoporosis
Postmenopausal women
Effect on bone mineral density
The efficacy of FOSAMAX 10 mg once daily in postmenopausal women, 44 to 84
years of age, with osteoporosis (lumbar spine bone mineral density [BMD] of
at least 2 standard deviations below the premenopausal mean) was demonstrated
in four double-blind, placebo-controlled clinical studies of two or three years'
duration. These included two three-year, multicenter studies of virtually identical
design, one performed in the United States (U.S.) and the other in 15 different
countries (Multinational), which enrolled 478 and 516 patients, respectively.
The following graph shows the mean increases in BMD of the lumbar spine, femoral
neck, and trochanter in patients receiving FOSAMAX 10 mg/day relative to placebo-treated
patients at three years for each of these studies.
Osteoporosis Treatment Studies in Postmenopausal Women Increase
in BMD
FOSAMAX 10 mg/day at Three Years
At three years significant increases in BMD, relative both to baseline and
placebo, were seen at each measurement site in each study in patients who received
FOSAMAX 10 mg/day. Total body BMD also increased significantly in each study,
suggesting that the increases in bone mass of the spine and hip did not occur
at the expense of other skeletal sites. Increases in BMD were evident as early
as three months and continued throughout the three years of treatment. (See
figures below for lumbar spine results.) In the two-year extension of these
studies, treatment of 147 patients with FOSAMAX 10 mg/day resulted in continued
increases in BMD at the lumbar spine and trochanter (absolute additional increases
between years 3 and 5: lumbar spine, 0.94%; trochanter, 0.88%). BMD at the femoral
neck, forearm and total body were maintained. FOSAMAX was similarly effective
regardless of age, race, baseline rate of bone turnover, and baseline BMD in
the range studied (at least 2 standard deviations below the premenopausal mean).
Thus, overall FOSAMAX reverses the loss of bone mineral density, a central factor
in the progression of osteoporosis.
Osteoporosis Treatment Studies in Postmenopausal Women
Time Course of Effect of FOSAMAX 10 mg/day versus placebo: Lumbar Spine BMD
Percent Change From Baseline
In patients with postmenopausal osteoporosis treated with FOSAMAX 10 mg/day for one or two years, the effects of treatment withdrawal were assessed. Following discontinuation, there were no further increases in bone mass and the rates of bone loss were similar to those of the placebo groups. These data indicate that continued treatment with FOSAMAX is required to maintain the effect of the drug.
The therapeutic equivalence of once weekly FOSAMAX 70 mg (n=519) and FOSAMAX
10 mg daily (n=370) was demonstrated in a one-year, double-blind, multicenter
study of postmenopausal women with osteoporosis. In the primary analysis of
completers, the mean increases from baseline in lumbar spine BMD at one year
were 5.1% (4.8, 5.4%; 95% CI) in the 70-mg once-weekly group (n=440) and 5.4%
(5.0, 5.8%; 95% CI) in the 10-mg daily group (n=330). The two treatment groups
were also similar with regard to BMD increases at other skeletal sites. The
results of the intention-to-treat analysis were consistent with the primary
analysis of completers.
Effect on fracture incidence
Data on the effects of FOSAMAX on fracture incidence are derived from three
clinical studies: 1) U.S. and Multinational combined: a study of patients with
a BMD T-score at or below minus 2.5 with or without a prior vertebral fracture,
2) Three-Year Study of the Fracture Intervention Trial (FIT): a study of patients
with at least one baseline vertebral fracture, and 3) Four-Year Study of FIT:
a study of patients with low bone mass but without a baseline vertebral fracture.
To assess the effects of FOSAMAX on the incidence of vertebral fractures (detected
by digitized radiography; approximately one third of these were clinically symptomatic),
the U.S. and Multinational studies were combined in an analysis that compared
placebo to the pooled dosage groups of FOSAMAX (5 or 10 mg for three years or
20 mg for two years followed by 5 mg for one year). There was a statistically
significant reduction in the proportion of patients treated with FOSAMAX experiencing
one or more new vertebral fractures relative to those treated with placebo (3.2%
vs. 6.2%; a 48% relative risk reduction). A reduction in the total number of
new vertebral fractures (4.2 vs. 11.3 per 100 patients) was also observed. In
the pooled analysis, patients who received FOSAMAX had a loss in stature that
was statistically significantly less than was observed in those who received
placebo (-3.0 mm vs. -4.6 mm).
The Fracture Intervention Trial (FIT) consisted of two studies in postmenopausal
women: the Three-Year Study of patients who had at least one baseline radiographic
vertebral fracture and the Four-Year Study of patients with low bone mass but
without a baseline vertebral fracture. In both studies of FIT, 96% of randomized
patients completed the studies (i.e., had a closeout visit at the scheduled
end of the study); approximately 80% of patients were still taking study medication
upon completion.
Fracture Intervention Trial: Three-Year Study (patients with at least one
baseline radiographic vertebral fracture)
This randomized, double-blind, placebo-controlled, 2027-patient study (FOSAMAX, n=1022; placebo, n=1005) demonstrated that treatment with FOSAMAX resulted in statistically significant reductions in fracture incidence at three years as shown in the table below.
Effect of FOSAMAX on Fracture Incidence in the Three-Year
Study of FIT
(patients with vertebral fracture at baseline)
| |
Percent of Patients |
FOSAMA
X
(n=1022) |
Placebo
(n=1005) |
Absolute Reduction in Fracture Incidence |
Relative Reduction in Fracture Risk % |
Patients with:
Vertebral fractures (diagnosed by X-ray)† |
| ≥ 1 new vertebral fracture |
7.9 |
15.0 |
7.1 |
47*** |
| ≥ 2 new vertebral fractures |
0.5 |
4.9 |
4.4 |
90*** |
| Clinical (symptomatic) fractures |
| Any clinical (symptomatic) fracture |
13.8 |
18.1 |
4.3 |
26‡ |
| ≥ 1 clinical (symptomatic) vertebral fracture |
2.3 |
5.0 |
2.7 |
54** |
| Hip fracture |
1.1 |
2.2 |
1.1 |
51* |
| Wrist (forearm) fracture |
2.2 |
4.1 |
1.9 |
48* |
†Number evaluable for vertebral
fractures: FOSAMAX, n=984; placebo, n=966
*p < 0.05, **p < 0.01, ***p < 0.001, ‡p=0.007
|
Furthermore, in this population of patients with baseline vertebral fracture, treatment with FOSAMAX significantly reduced the incidence of hospitalizations (25.0% vs. 30.7%).
In the Three-Year Study of FIT, fractures of the hip occurred in 22 (2.2%)
of 1005 patients on placebo and 11 (1.1%) of 1022 patients on FOSAMAX, p=0.047.
The figure below displays the cumulative incidence of hip fractures in this
study.
Cumulative Incidence of Hip Fractures in the Three-Year Study
of FIT
(patients with radiographic vertebral fracture at baseline)
Fracture Intervention Trial: Four-Year Study (patients with low bone mass
but without a baseline radiographic vertebral fracture)
This randomized, double-blind, placebo-controlled, 4432-patient study (FOSAMAX, n=2214; placebo, n=2218) further investigated the reduction in fracture incidence due to FOSAMAX. The intent of the study was to recruit women with osteoporosis, defined as a baseline femoral neck BMD at least two standard deviations below the mean for young adult women. However, due to subsequent revisions to the normative values for femoral neck BMD, 31% of patients were found not to meet this entry criterion and thus this study included both osteoporotic and non-osteoporotic women. The results are shown in the table below for the patients with osteoporosis.
Effect of FOSAMAX on Fracture Incidence in Osteoporotic†
Patients in the Four-Year Study of FIT (patients without vertebral fracture
at baseline)
| |
Percent of Patients |
FOSAMA
X
(n=1545) |
Placebo
(n=1521) |
Absolute Reduction in Fracture Incidence |
Relative Reduction in Fracture Risk (%) |
Patients with:
Vertebral fractures (diagnosed by X-ray)†† |
| ≥ 1 new vertebral fracture |
2.5 |
4.8 |
2.3 |
48*** |
| ≥ 2 new vertebral fractures |
0.1 |
0.6 |
0.5 |
78* |
| Clinical (symptomatic) fractures |
| Any clinical (symptomatic) fracture |
12.9 |
16.2 |
3.3 |
22** |
| ≥ 1 clinical (symptomatic) vertebral fracture |
1.0 |
1.6 |
0.6 |
41 (NS)††† |
| Hip fracture |
1.0 |
1.4 |
0.4 |
29 (NS)††† |
| Wrist (forearm) fracture |
3.9 |
3.8 |
-0.1 |
NS††† |
†Baseline femoral neck
BMD at least 2 SD below the mean for young adult women
††Number evaluable for vertebral fractures: FOSAMAX,
n=1426; placebo, n=1428
†††Not significant. This study was not
powered to detect differences at these sites.
*p=0.035, ** p=0.01, ***p < 0.001 |
Fracture results across studies
In the Three-Year Study of FIT, FOSAMAX reduced the percentage of women experiencing
at least one new radiographic vertebral fracture from 15.0% to 7.9% (47% relative
risk reduction, p < 0.001); in the Four-Year Study of FIT, the percentage was
reduced from 3.8% to 2.1% (44% relative risk reduction, p=0.001); and in the
combined U.S./Multinational studies, from 6.2% to 3.2% (48% relative risk reduction,
p=0.034).
FOSAMAX reduced the percentage of women experiencing multiple (two or more)
new vertebral fractures from 4.2% to 0.6% (87% relative risk reduction, p < 0.001)
in the combined U.S./Multinational studies and from 4.9% to 0.5% (90% relative
risk reduction, p < 0.001) in the Three-Year Study of FIT. In the Four-Year
Study of FIT, FOSAMAX reduced the percentage of osteoporotic women experiencing
multiple vertebral fractures from 0.6% to 0.1% (78% relative risk reduction,
p=0.035).
Thus, FOSAMAX reduced the incidence of radiographic vertebral fractures in
osteoporotic women whether or not they had a previous radiographic vertebral
fracture.
FOSAMAX, over a three- or four-year period, was associated with statistically
significant reductions in loss of height vs. placebo in patients with and without
baseline radiographic vertebral fractures. At the end of the FIT studies the
between-treatment group differences were 3.2 mm in the Three-Year Study and
1.3 mm in the Four-Year Study.
Bone histology
Bone histology in 270 postmenopausal patients with osteoporosis treated with FOSAMAX at doses ranging from 1 to 20 mg/day for one, two, or three years revealed normal mineralization and structure, as well as the expected decrease in bone turnover relative to placebo. These data, together with the normal bone histology and increased bone strength observed in rats and baboons exposed to long-term alendronate treatment, support the conclusion that bone formed during therapy with FOSAMAX is of normal quality.
Men
The efficacy of FOSAMAX in men with hypogonadal or idiopathic osteoporosis
was demonstrated in two clinical studies.
A two-year, double-blind, placebo-controlled, multicenter study of FOSAMAX
10 mg once daily enrolled a total of 241 men between the ages of 31 and 87 (mean,
63). All patients in the trial had either: 1) a BMD T-score ≤ -2 at the femoral
neck and ≤ -1 at the lumbar spine, or 2) a baseline osteoporotic fracture
and a BMD T-score ≤ -1 at the femoral neck. At two years, the mean increases
relative to placebo in BMD in men receiving FOSAMAX 10 mg/day were significant
at the following sites: lumbar spine, 5.3%; femoral neck, 2.6%; trochanter,
3.1%; and total body, 1.6%. Treatment with FOSAMAX also reduced height loss
(FOSAMAX, -0.6 mm vs. placebo, -2.4 mm).
A one-year, double-blind, placebo-controlled, multicenter study of once weekly
FOSAMAX 70 mg enrolled a total of 167 men between the ages of 38 and 91 (mean,
66). Patients in the study had either: 1) a BMD T-score - ≤ 2 at the femoral
neck and - ≤ 1 at the lumbar spine, 2) a BMD T-score - ≤ 2 at the lumbar spine
and - ≤ 1 at the femoral neck, or 3) a baseline osteoporotic fracture and a
BMD T-score - ≤ 1 at the femoral neck. At one year, the mean increases relative
to placebo in BMD in men receiving FOSAMAX 70 mg once weekly were significant
at the following sites: lumbar spine, 2.8%; femoral neck, 1.9%; trochanter,
2.0%; and total body, 1.2%. These increases in BMD were similar to those seen
at one year in the 10 mg once-daily study.
In both studies, BMD responses were similar regardless of age ( ≥ 65 years vs.
< 65 years), gonadal function (baseline testosterone < 9 ng/dL vs. ≥ 9 ng/dL),
or baseline BMD (femoral neck and lumbar spine T-score ≤ -2.5 vs. > -2.5).
Prevention of osteoporosis in postmenopausal women
Prevention of bone loss was demonstrated in two double-blind, placebo-controlled
studies of postmenopausal women 40-60 years of age. One thousand six hundred
nine patients (FOSAMAX 5 mg/day; n=498) who were at least six months postmenopausal
were entered into a two-year study without regard to their baseline BMD. In
the other study, 447 patients (FOSAMAX 5 mg/day; n=88), who were between six
months and three years postmenopause, were treated for up to three years. In
the placebo-treated patients BMD losses of approximately 1% per year were seen
at the spine, hip (femoral neck and trochanter) and total body. In contrast,
FOSAMAX 5 mg/day prevented bone loss in the majority of patients and induced
significant increases in mean bone mass at each of these sites (see figures
below). In addition, FOSAMAX 5 mg/day reduced the rate of bone loss at the
forearm by approximately half relative to placebo. FOSAMAX 5 mg/day was similarly
effective in this population regardless of age, time since menopause, race and
baseline rate of bone turnover.
Osteoporosis Treatment Studies in Postmenopausal Women
The therapeutic equivalence of once weekly FOSAMAX 35 mg (n=362) and FOSAMAX 5 mg daily (n=361) was demonstrated in a one-year, double-blind, multicenter study of postmenopausal women without osteoporosis. In the primary analysis of completers, the mean increases from baseline in lumbar spine BMD at one year were 2.9% (2.6, 3.2%; 95% CI) in the 35-mg once-weekly group (n=307) and 3.2% (2.9, 3.5%; 95% CI) in the 5-mg daily group (n=298). The two treatment groups were also similar with regard to BMD increases at other skeletal sites. The results of the intention-to-treat analysis were consistent with the primary analysis of completers.
Bone histology
Bone histology was normal in the 28 patients biopsied at the end of three years who received FOSAMAX at doses of up to 10 mg/day.
Concomitant use with estrogen/hormone replacement therapy (HRT)
The effects on BMD of treatment with FOSAMAX 10 mg once daily and conjugated
estrogen (0.625 mg/day) either alone or in combination were assessed in a two-year,
double-blind, placebo-controlled study of hysterectomized postmenopausal osteoporotic
women (n=425). At two years, the increases in lumbar spine BMD from baseline
were significantly greater with the combination (8.3%) than with either estrogen
or FOSAMAX alone (both 6.0%).
The effects on BMD when FOSAMAX was added to stable doses (for at least one
year) of HRT (estrogen ± progestin) were assessed in a one-year, double-blind,
placebo-controlled study in postmenopausal osteoporotic women (n=428). The addition
of FOSAMAX 10 mg once daily to HRT produced, at one year, significantly greater
increases in lumbar spine BMD (3.7%) vs. HRT alone (1.1%). In these studies,
significant increases or favorable trends in BMD for combined therapy compared
with HRT alone were seen at the total hip, femoral neck, and trochanter. No
significant effect was seen for total body BMD.
Histomorphometric studies of transiliac biopsies in 92 subjects showed normal
bone architecture. Compared to placebo there was a 98% suppression of bone turnover
(as assessed by mineralizing surface) after 18 months of combined treatment
with FOSAMAX and HRT, 94% on FOSAMAX alone, and 78% on HRT alone. The long-term
effects of combined FOSAMAX and HRT on fracture occurrence and fracture healing
have not been studied.
Glucocorticoid-induced osteoporosis
The efficacy of FOSAMAX 5 and 10 mg once daily in men and women receiving glucocorticoids
(at least 7.5 mg/day of prednisone or equivalent) was demonstrated in two, one-year,
double-blind, randomized, placebo-controlled, multicenter studies of virtually
identical design, one performed in the United States and the other in 15 different
countries (Multinational [which also included FOSAMAX 2.5 mg/day]). These studies
enrolled 232 and 328 patients, respectively, between the ages of 17 and 83 with
a variety of glucocorticoid-requiring diseases. Patients received supplemental
calcium and vitamin D. The following figure shows the mean increases relative
to placebo in BMD of the lumbar spine, femoral neck, and trochanter in patients
receiving FOSAMAX 5 mg/day for each study.
Studies in Glucocorticoid - Treated Patients Increase in
BMD FOSAMAX 5 mg/day at One Year
After one year, significant increases relative to placebo in BMD were seen
in the combined studies at each of these sites in patients who received FOSAMAX
5 mg/day. In the placebo-treated patients, a significant decrease in BMD occurred
at the femoral neck (-1.2%), and smaller decreases were seen at the lumbar spine
and trochanter. Total body BMD was maintained with FOSAMAX 5 mg/day. The increases
in BMD with FOSAMAX 10 mg/day were similar to those with FOSAMAX 5 mg/day in
all patients except for postmenopausal women not receiving estrogen therapy.
In these women, the increases (relative to placebo) with FOSAMAX 10 mg/day were
greater than those with FOSAMAX 5 mg/day at the lumbar spine (4.1% vs. 1.6%)
and trochanter (2.8% vs. 1.7%), but not at other sites. FOSAMAX was effective
regardless of dose or duration of glucocorticoid use. In addition, FOSAMAX was
similarly effective regardless of age ( < 65 vs. ≥ 65 years), race (Caucasian
vs. other races), gender, underlying disease, baseline BMD, baseline bone turnover,
and use with a variety of common medications.
Bone histology was normal in the 49 patients biopsied at the end of one year
who received FOSAMAX at doses of up to 10 mg/day.
Of the original 560 patients in these studies, 208 patients who remained on
at least 7.5 mg/day of prednisone or equivalent continued into a one-year double-blind
extension. After two years of treatment, spine BMD increased by 3.7% and 5.0%
relative to placebo with FOSAMAX 5 and 10 mg/day, respectively. Significant
increases in BMD (relative to placebo) were also observed at the femoral neck,
trochanter, and total body.
After one year, 2.3% of patients treated with FOSAMAX 5 or 10 mg/day (pooled) vs. 3.7% of those treated with placebo experienced a new vertebral fracture (not significant). However, in the population studied for two years, treatment with FOSAMAX (pooled dosage groups: 5 or 10 mg for two years or 2.5 mg for one year followed by 10 mg for one year) significantly reduced the incidence of patients with a new vertebral fracture (FOSAMAX 0.7% vs. placebo 6.8%).
Paget's disease of bone
The efficacy of FOSAMAX 40 mg once daily for six months was demonstrated in
two double-blind clinical studies of male and female patients with moderate
to severe Paget's disease (alkaline phosphatase at least twice the upper limit
of normal): a placebo-controlled, multinational study and a U.S. comparative
study with etidronate disodium 400 mg/day. The following figure shows the mean
percent changes from baseline in serum alkaline phosphatase for up to six months
of randomized treatment.
Studies in Paget's Disease of Bone Effect on Serum Alkaline
Phosphatase of FOSAMAX 40 mg/day Versus Placebo or Etidronate 400 mg/day
At six months the suppression in alkaline phosphatase in patients treated with
FOSAMAX was significantly greater than that achieved with etidronate and contrasted
with the complete lack of response in placebo-treated patients. Response (defined
as either normalization of serum alkaline phosphatase or decrease from baseline
≥ 60%) occurred in approximately 85% of patients treated with FOSAMAX in the
combined studies vs. 30% in the etidronate group and 0% in the placebo group.
FOSAMAX was similarly effective regardless of age, gender, race, prior use of
other bisphosphonates, or baseline alkaline phosphatase within the range studied
(at least twice the upper limit of normal).
Bone histology was evaluated in 33 patients with Paget's disease treated with
FOSAMAX 40 mg/day for 6 months. As in patients treated for osteoporosis (see
Clinical Studies, Treatment of osteoporosis in postmenopausal women, Bone
histology), FOSAMAX did not impair mineralization, and the expected decrease
in the rate of bone turnover was observed. Normal lamellar bone was produced
during treatment with FOSAMAX, even where preexisting bone was woven and disorganized.
Overall, bone histology data support the conclusion that bone formed during
treatment with FOSAMAX is of normal quality.
Animal Pharmacology
The relative inhibitory activities on bone resorption and mineralization of alendronate and etidronate were compared in the Schenk assay, which is based on histological examination of the epiphyses of growing rats. In this assay, the lowest dose of alendronate that interfered with bone mineralization (leading to osteomalacia) was 6000-fold the antiresorptive dose. The corresponding ratio for etidronate was one to one. These data suggest that alendronate administered in therapeutic doses is highly unlikely to induce osteomalacia.
Last updated on RxList: 12/2/2008