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Mechanism of Action

Risedronate has an affinity for hydroxyapatite crystals in bone and acts as an antiresorptive agent. At the cellular level, risedronate inhibits osteoclasts. The osteoclasts adhere normally to the bone surface, but show evidence of reduced active resorption (for example, lack of ruffled border). Histomorphometry in rats, dogs, and minipigs showed that risedronate treatment reduces bone turnover (activation frequency, that is, the rate at which bone remodeling sites are activated) and bone resorption at remodeling sites.


Risedronate treatment decreases the elevated rate of bone turnover that is typically seen in postmenopausal osteoporosis. In clinical trials, administration of risedronate sodium immediate- release to postmenopausal women resulted in decreases in biochemical markers of bone turnover, including urinary deoxypyridinoline/creatinine and urinary collagen cross-linked Ntelopeptide (markers of bone resorption) and serum bone-specific alkaline phosphatase (a marker of bone formation). At the 5 mg daily dose, decreases in deoxypyridinoline/creatinine were evident within 14 days of treatment. Changes in bone formation markers were observed later than changes in resorption markers, as expected, due to the coupled nature of bone resorption and bone formation; decreases in bone-specific alkaline phosphatase of about 20% were evident within 3 months of treatment. Bone turnover markers reached a nadir of about 40% below baseline values by the sixth month of treatment and remained stable with continued treatment for up to 3 years. Bone turnover is decreased as early as 14 days and maximally within about 6 months of treatment, with achievement of a new steady-state that more nearly approximates the rate of bone turnover seen in premenopausal women. In a 1-year study comparing Atelvia 35 mg weekly taken immediately after breakfast versus risedronate sodium immediate-release 5 mg daily oral dosing regimens in postmenopausal women, mean decreases from baseline at 1 year in urinary collagen cross-linked N-telopeptide were 47% in the Atelvia 35 mg once-a-week following breakfast group and 42% in the risedronate sodium immediate-release 5 mg daily group. In addition, serum bone-specific alkaline phosphatase at 1 year was reduced by 33% in the Atelvia 35 mg once-a-week following breakfast group and 32% in the risedronate sodium immediate-release 5 mg daily group.



The mean absolute oral bioavailability of the 30 mg risedronate sodium immediate-release tablet taken 4 hours prior to a meal is 0.63% (90% confidence interval [CI]: 0.54% to 0.75%) and is similar to an oral solution. The time to peak concentration (Tmax) for Atelvia tablet is approximately 3 hours when administered in the morning 4 hours prior to a meal.

Food Effect

In a crossover pharmacokinetic study, the bioavailability of Atelvia 35 mg delayed-release tablets decreased by approximately 30% when administered immediately after a high-fat breakfast compared to administration in the morning 4 hours before a meal.

The bioavailability of the 35 mg Atelvia tablet administered after a high-fat breakfast was similar to risedronate sodium 35 mg immediate-release tablet dosed 4 hours before a meal in one study and was approximately 2- to 4-fold greater than the immediate-release 35 mg tablet administered 30 minutes prior to a high-fat breakfast.

In a separate study, Atelvia administered after dinner exhibited approximately 87% increase in risedronate exposure compared to administration following a breakfast. The safety and efficacy of dosing Atelvia after dinner has not been evaluated [see DOSAGE AND ADMINISTRATION].


The mean steady-state volume of distribution for risedronate is 13.8 L/kg in humans. Human plasma protein binding of drug is about 24%. Preclinical studies in rats and dogs dosed intravenously with single doses of [14C] risedronate indicate that approximately 60% of the dose is distributed to bone. The remainder of the dose is excreted in the urine. After multiple oral dosing in rats, the uptake of risedronate in soft tissues was in the range of 0.001% to 0.01%.


There is no evidence of systemic metabolism of risedronate.


In young healthy subjects, approximately half of the absorbed dose of risedronate was excreted in urine within 24 hours, and 85% of an intravenous dose was recovered in the urine over 28 days. Based on simultaneous modeling of serum and urine data for the risedronate sodium immediate-release tablets, mean renal clearance was 105 mL/min (CV = 34%) and mean total clearance was 122 mL/min (CV = 19%), with the difference primarily reflecting nonrenal clearance or clearance due to adsorption to bone. The renal clearance is not concentration dependent, and there is a linear relationship between renal clearance and creatinine clearance. Unabsorbed drug is eliminated unchanged in feces. In osteopenic postmenopausal women, the terminal exponential half-life was 561 hours, mean renal clearance was 52 mL/min (CV = 25%), and mean total clearance was 73 mL/min (CV = 15%).

Specific Populations

Pediatric: Atelvia is not indicated for use in pediatric patients [see Pediatric Use].

Geriatric: Effect of age on bioavailability of Atelvia has not been evaluated. Based on data from risedronate immediate-release tablet, bioavailability and disposition of risedronate are similar in elderly (greater than 60 years of age) and younger subjects. No dosage adjustment is necessary.

Race: Pharmacokinetic differences due to race have not been studied. The clinical trial of Atelvia was conducted mostly in Caucasians.

Renal Impairment: Risedronate is excreted unchanged primarily via the kidney. As compared to persons with normal renal function, the renal clearance of risedronate was decreased by about 70% in patients with creatinine clearance of approximately 30 mL/min. Atelvia is not recommended for use in patients with severe renal impairment (creatinine clearance less than 30 mL/min). No dosage adjustment is necessary in patients with a creatinine clearance greater than or equal to 30 mL/min.

Hepatic Impairment: No studies have been performed to assess risedronate's safety or efficacy in patients with hepatic impairment. Risedronate is not metabolized in rat, dog, and human liver preparations. Insignificant amounts (less than 0.1% of intravenous dose) of drug are excreted in the bile in rats. Therefore, dosage adjustment is unlikely to be needed in patients with hepatic impairment.

Drug Interactions

Risedronate is not metabolized and does not induce or inhibit hepatic microsomal drug-metabolizing enzymes (for example, Cytochrome P450).

Calcium supplement: A Phase 1 single-dose, cross-over study in 101 postmenopausal women evaluated the relative bioavailability of Atelvia 35 mg delayed-release tablets taken after breakfast and following a 600 mg elemental calcium/400 international units vitamin D supplement, compared to Atelvia alone taken after breakfast without calcium or vitamin D supplemention. The addition of the calcium/vitamin D supplement following the meal resulted in an approximate 38% reduction in the amount of risedronate absorbed [see DRUG INTERACTIONS].

Proton Pump Inhibitors: A Phase 1, 2-period, cross-over study in 60 healthy postmenopausal female subjects evaluated the relative bioavailability of a single dose Atelvia 35 mg delayed-release tablet taken after breakfast following 6 days of esomeprazole magnesium delayed release 40 mg capsules. On Day 6, esomeprazole 40 mg capsule was administered with 240 mL water one hour before breakfast and Atelvia 35 mg tablet was administered with 240 mL water within 10 minutes after a standard breakfast. The Cmax and AUCinf of risedronate were increased by 60 percent and 22 percent, respectively, in presence of esomeprazole.

Animal Toxicology and/or Pharmacology

Risedronate demonstrated potent anti-osteoclast, antiresorptive activity in ovariectomized rats and minipigs. Bone mass and biomechanical strength were increased dose-dependently at daily oral doses up to 4 and 25 times the recommended human dose of 5 mg/day for rats and minipigs, respectively. Risedronate treatment maintained the positive correlation between BMD and bone strength and did not have a negative effect on bone structure or mineralization. In intact dogs, risedronate induced positive bone balance at the level of the bone remodeling unit at oral doses ranging from 0.5 to 1.5 times the human dose of 5 mg/day.

In dogs treated with an oral dose approximately 5 times the human dose of 5 mg/day, risedronate caused a delay in fracture healing of the radius. The observed delay in fracture healing is similar to other bisphosphonates. This effect did not occur at a dose approximately 0.5 times the human daily dose.

The Schenk rat assay, based on histologic examination of the epiphyses of growing rats after drug treatment, demonstrated that risedronate did not interfere with bone mineralization even at the highest dose tested, which was approximately 3500 times the lowest antiresorptive dose in this model (1.5 mcg/kg/day) and approximately 800 times the human dose of 5 mg/day. This indicates that Atelvia administered at the therapeutic dose is unlikely to induce osteomalacia.

Dosing multiples provided above are based on the recommended human osteoporosis dose of 5 mg/day and normalized using body surface area (mg/m²).

Clinical Studies

Treatment of Osteoporosis in Postmenopausal Women

The efficacy of Atelvia 35 mg once-a-week in the treatment of postmenopausal osteoporosis was demonstrated in a randomized, double-blind, active-control trial of approximately 900 subjects. All patients in this study received supplemental calcium (1000 mg/day) and vitamin D (800 to 1000 international units/day). The primary efficacy endpoint was percent change in lumbar spine bone mineral density at 1 year.

Atelvia 35 mg once-a-week administered after breakfast was shown to be non-inferior to risedronate sodium immediate-release 5 mg daily. Table 2 presents the primary efficacy analysis, percent change in lumbar spine BMD, in the intent-to-treat population with last observation carried forward (LOCF).

Table 2 : Lumbar Spine BMD - Percent Change from Baseline at Endpointa

  Risedronate sodium immediate-release 5 mg Daily
N = 307
Atelvia 35 mg Once-a-Week Following Breakfast
N = 307
Primary Efficacy (LOCF)
  n 270 261
  LS Mean (95% CI) 3.1* (2.7, 3.5) 3.3* (2.9, 3.7)
  LS Mean Differenceb (95% CI) -0.2 (-0.8, 0.3)
N = number of intent-to-treat patients within specified treatment; n = number of patients with values at the visit.
*Indicates a statistically significant difference from baseline determined from 95% CI unadjusted for multiple comparisons.
LS = Least Squares
a at 1 year LOCF
b LS Mean Difference is 5 mg daily minus 35 mg weekly treatment.

Fracture efficacy with risedronate sodium immediate-release 5 mg daily

The fracture efficacy of risedronate sodium immediate-release 5 mg daily in the treatment of postmenopausal osteoporosis was demonstrated in 2 large, randomized, placebo-controlled, double-blind studies that enrolled a total of almost 4000 postmenopausal women under similar protocols. The Multinational study (VERT MN) (risedronate sodium immediate-release 5 mg daily, N = 408) was conducted primarily in Europe and Australia; a second study was conducted in North America (VERT NA) (risedronate sodium immediate-release 5 mg daily, N = 821). Patients were selected on the basis of radiographic evidence of previous vertebral fracture, and therefore, had established disease. The average number of prevalent vertebral fractures per patient at study entry was 4 in VERT MN, and 2.5 in VERT NA, with a broad range of baseline BMD levels. All patients in these studies received supplemental calcium 1000 mg/day. Patients with low 25-hydroxyvitamin D3 levels (approximately 40 nmol/L or less) also received 500 international units/day supplemental vitamin D.

Effect on Vertebral Fractures

Fractures of previously undeformed vertebrae (new fractures) and worsening of pre-existing vertebral fractures were diagnosed radiographically; some of these fractures were also associated with symptoms (that is, clinical fractures). Spinal radiographs were scheduled annually and prospectively planned analyses were based on the time to a patient's first diagnosed fracture. The primary endpoint for these studies was the incidence of new and worsening vertebral fractures across the period of 0 to 3 years. Risedronate sodium immediate-release 5 mg daily significantly reduced the incidence of new and worsening vertebral fractures and of new vertebral fractures in both VERT NA and VERT MN at all time points (Table 3). The reduction in risk seen in the subgroup of patients who had 2 or more vertebral fractures at study entry was similar to that seen in the overall study population.

Table 3 : The Effect of Risedronate sodium 5 mg Immediate-Release Daily on the Risk of Vertebral Fractures

VERT NA Proportion of Patients with Fracture (%) a Absolute Risk Relative Risk
N = 678
Risedronate sodium 5 mg
N = 696
Reduction (%) Reduction (%)
New and Worsening
  0 to 1 Year 7.2 3.9 3.3 49
  0 to 2 Years 12.8 8.0 4.8 42
  0 to 3 Years 18.5 13.9 4.6 33
  0 to 1 Year 6.4 2.4 4.0 65
  0 to 2 Years 11.7 5.8 5.9 55
  0 to 3 Years 16.3 11.3 5.0 41
VERT MN Placebo
N = 346
Risedronate sodium 5 mg N = 344 Absolute Risk Reduction (%) Relative Risk Reduction (%)
New and Worsening
  0 to 1 Year 15.3 8.2 7.1 50
  0 to 2 Years 28.3 13.9 14.4 56
  0 to 3 Years 34.0 21.8 12.2 46
  0 to 1 Year 13.3 5.6 7.7 61
  0 to 2 Years 24.7 11.6 13.1 59
  0 to 3 Years 29.0 18.1 10.9 49
aCalculated by Kaplan-Meier methodology.

Effect on Osteoporosis-Related Nonvertebral Fractures

In VERT MN and VERT NA, a prospectively planned efficacy endpoint was defined consisting of all radiographically confirmed fractures of skeletal sites accepted as associated with osteoporosis. Fractures at these sites were collectively referred to as osteoporosis-related nonvertebral fractures. Risedronate sodium immediate-release 5 mg daily significantly reduced the incidence of nonvertebral osteoporosis-related fractures over 3 years in VERT NA (8% versus 5%; relative risk reduction 39%) and reduced the fracture incidence in VERT MN from 16% to 11%. There was a significant reduction from 11% to 7% when the studies were combined, with a corresponding 36% reduction in relative risk. Figure 1 shows the overall results as well as the results at the individual skeletal sites for the combined studies.

Figure 1: Nonvertebral Osteoporosis-Related Fractures Cumulative Incidence Over 3 Years Combined VERT MN and VERT NA

Nonvertebral Osteoporosis-Related Fractures Cumulative Incidence Over 3 Years Combined VERT MN and VERT NA - Illustration


Bone biopsies from 110 postmenopausal women were obtained at endpoint in the VERT NA study. Patients had received placebo or daily risedronate sodium immediate-release (2.5 mg or 5 mg) for 2 to 3 years. Histologic evaluation (N = 103) showed no osteomalacia, impaired bone mineralization, or other adverse effects on bone in risedronate sodium immediate-release treated women. These findings demonstrate that bone formed during risedronate sodium immediate-release administration is of normal quality. The histomorphometric parameter mineralizing surface, an index of bone turnover, was assessed based upon baseline and post-treatment biopsy samples from 21 treated with placebo and 23 patients treated with risedronate sodium immediate-release 5 mg daily. Mineralizing surface decreased moderately in risedronate sodium immediate-release treated patients (median percent change: placebo, -21%; risedronate sodium immediate-release 5 mg daily, -74%), consistent with the known effects of treatment on bone turnover.

Effect on Height

In the two 3-year osteoporosis treatment studies, standing height was measured yearly by stadiometer. Both risedronate sodium immediate-release 5 mg daily and placebo-treated groups lost height during the studies. Patients who received risedronate sodium immediate-release 5 mg daily had a statistically significantly smaller loss of height than those who received placebo. In VERT MN, the median annual height change was -2.4 mm/yr in the placebo group compared to -1.3 mm/yr in the risedronate sodium immediate-release 5 mg daily group. In VERT NA, the median annual height change was -1.1 mm/yr in the placebo group compared to -0.7 mm/yr in the risedronate sodium immediate-release 5 mg daily group.

Effect on Bone Mineral Density

The results of 4 randomized, placebo-controlled trials in women with postmenopausal osteoporosis (VERT MN, VERT NA, BMD MN, BMD NA) demonstrate that risedronate sodium immediate-release 5 mg daily increases BMD at the spine, hip, and wrist compared to the effects seen with placebo. Table 4 displays the significant increases in BMD seen at the lumbar spine, femoral neck, femoral trochanter, and midshaft radius in these trials compared to placebo. In both VERT studies (VERT MN and VERT NA), risedronate sodium immediate-release 5 mg daily produced increases in lumbar spine BMD that were progressive over the 3 years of treatment, and were statistically significant relative to baseline and to placebo at 6 months and at all later time points.

Table 4 : Mean Percent Increase in BMD from Baseline in Patients Taking Risedronate sodium Immediate-Release 5 mg or Placebo at Endpointa

N = 323
5 mg
N = 323
N = 599
5 mg
N = 606
N = 161
5 mg
N = 148
N = 191
5 mg
N = 193
Lumbar Spine 1.0 6.6 0.8 5.0 0.0 4.0 0.2 4.8
Femoral Neck -1.4 1.6 -1.0 1.4 -1.1 1.3 0.1 2.4
Femoral -1.9 3.9 -0.5 3.0 -0.6 2.5 1.3 4.0
Midshaft Radius -1.5* 0.2* -1.2* 0.1* ND ND
aThe endpoint value is the value at the study's last time point for all patients who had BMD measured at that time; otherwise the last post-baseline BMD value prior to the study's last time point is used.
bThe duration of the studies was 3 years.
cThe duration of the studies was 1.5 to 2 years.
*BMD of the midshaft radius was measured in a subset of centers in VERT MN (placebo, N = 222; 5 mg, N = 214) and VERT NA (placebo, N = 310; 5 mg, N = 306).
ND = analysis not done

Last reviewed on RxList: 5/3/2013
This monograph has been modified to include the generic and brand name in many instances.


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