Risedronate Sodium (Page 4 of 9)

8.5 Geriatric Use

Of the patients receiving risedronate sodium tablets in postmenopausal osteoporosis studies [see Clinical Studies (14)], 47% were between 65 and 75 years of age, and 17% were over 75. The corresponding proportions were 26% and 11% in glucocorticoid-induced osteoporosis trials, and 40% and 26% in Paget’s disease trials. No overall differences in efficacy between geriatric and younger patients were observed in these studies. In the male osteoporosis trial, 28% of patients receiving risedronate sodium tablets were between 65 and 75 years of age and 9% were over 75. The lumbar spine BMD response for risedronate sodium tablets compared to placebo was 5.6% for subjects less than 65 years and 2.9% for subjects greater than or equal to 65 years. No overall differences in safety between geriatric and younger patients were observed in the risedronate sodium trials, but greater sensitivity of some older individuals cannot be ruled out.

8.6 Renal Impairment

Risedronate sodium tablets are not recommended for use in patients with severe renal impairment (creatinine clearance less than 30 mL/min) because of lack of clinical experience. No dosage adjustment is necessary in patients with a creatinine clearance greater than or equal to 30 mL/min.

8.7 Hepatic Impairment

No studies have been performed to assess risedronate’s safety or efficacy in patients with hepatic impairment. Risedronate is not metabolized in human liver preparations. Dosage adjustment is unlikely to be needed in patients with hepatic impairment.

10 OVERDOSAGE

Decreases in serum calcium and phosphorus following substantial overdose may be expected in some patients. Signs and symptoms of hypocalcemia may also occur in some of these patients. Milk or antacids containing calcium should be given to bind risedronate sodium and reduce absorption of the drug.

In cases of substantial overdose, gastric lavage may be considered to remove unabsorbed drug. Standard procedures that are effective for treating hypocalcemia, including the administration of calcium intravenously, would be expected to restore physiologic amounts of ionized calcium and to relieve signs and symptoms of hypocalcemia.

Lethality after single oral doses was seen in female rats at 903 mg/kg and male rats at 1703 mg/kg. The minimum lethal dose in mice and rabbits was 4000 mg/kg and 1000 mg/kg, respectively. These values represent 320 to 620 times the 30 mg human dose based on surface area (mg/m2).

11 DESCRIPTION

Risedronate sodium tablets, USP are pyridinyl bisphosphonates that inhibit osteoclast-mediated bone resorption and modulate bone metabolism. Each risedronate sodium tablet, USP for oral administration contains the equivalent of 35, 75, or 150 mg of anhydrous risedronate sodium in the form of the hemi-pentahydrate. The empirical formula for risedronate sodium hemi-pentahydrate is C7 H10 NO7 P2 Na •2.5 H2 O. The chemical name of risedronate sodium is [1-hydroxy-2-(3-pyridinyl)ethylidene]bis[phosphonic acid] monosodium salt. The chemical structure of risedronate sodium hemi-pentahydrate is the following:

risedronatestructure

Molecular Weight:
Anhydrous: 305.10
Hemi-pentahydrate: 350.13

Risedronate sodium, USP is a white powder. It is soluble in water and essentially insoluble in common organic solvents.

Inactive Ingredients

All dose strengths contain: anhydrous lactose, crospovidone, hydroxypropyl cellulose, hypromellose, magnesium stearate, polyethylene glycol, silicon dioxide, and titanium dioxide.

Dose strength-specific ingredients include: 35 mg—ferric oxide red, ferric oxide yellow; 75 mg—ferric oxide red; 150 mg -FD&C blue #2, sodium phosphate monobasic monohydrate, sodium phosphate dibasic.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Risedronate sodium has an affinity for hydroxyapatite crystals in bone and acts as an antiresorptive agent. At the cellular level, risedronate sodium 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 sodium treatment reduces bone turnover (activation frequency, that is, the rate at which bone remodeling sites are activated) and bone resorption at remodeling sites.

12.2 Pharmacodynamics

Risedronate sodium treatment decreases the elevated rate of bone turnover that is typically seen in postmenopausal osteoporosis. In clinical trials, administration of risedronate sodium to postmenopausal women resulted in decreases in biochemical markers of bone turnover, including urinary deoxypyridinoline/creatinine and urinary collagen cross-linked N-telopeptide (markers of bone resorption) and serum bone-specific alkaline phosphatase (a marker of bone formation). At the 5 mg 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 daily versus weekly oral dosing regimens of risedronate sodium for the treatment of osteoporosis in postmenopausal women, risedronate sodium tablets 5 mg daily and risedronate sodium tablets 35 mg once-a-week decreased urinary collagen cross-linked N-telopeptide by 60% and 61%, respectively. In addition, serum bone-specific alkaline phosphatase was also reduced by 42% and 41% in the risedronate sodium tablets 5 mg daily and risedronate sodium tablets 35 mg once-a-week groups, respectively. When postmenopausal women with osteoporosis were treated for 1 year with risedronate sodium tablets 5 mg daily or risedronate sodium tablets 75 mg two consecutive days per month, urinary collagen cross-linked N-telopeptide was decreased by 54% and 52%, respectively, and serum bone-specific alkaline phosphatase was reduced by 36% and 35%, respectively. In a 1–year study comparing risedronate sodium tablets 5 mg daily versus risedronate sodium tablets 150 mg once-a-month in women with postmenopausal osteoporosis, urinary collagen cross-linked N-telopeptide was decreased by 52% and 49%, respectively, and serum bone-specific alkaline phosphatase was reduced by 31% and 32%, respectively.

Osteoporosis in Men
In a 2-year study of men with osteoporosis, treatment with risedronate sodium tablets 35 mg once-a-week resulted in a mean decrease from baseline compared to placebo of 16% (placebo 20%; risedronate sodium tablets 35 mg 37%) for the bone resorption marker urinary collagen cross-linked N-telopeptide, 45% (placebo -6%; risedronate sodium tablets 35 mg 39%) for the bone resorption marker serum C-telopeptide, and 27% (placebo -2%; risedronate sodium tablets 35 mg 25%) for the bone formation marker serum bone-specific alkaline phosphatase.

Glucocorticoid-Induced Osteoporosis

Osteoporosis with glucocorticoid use occurs as a result of inhibited bone formation and increased bone resorption resulting in net bone loss. Risedronate sodium decreases bone resorption without directly inhibiting bone formation.

In two 1-year clinical trials in the treatment and prevention of glucocorticoid-induced osteoporosis, risedronate sodium tablets 5 mg decreased urinary collagen cross-linked N-telopeptide (a marker of bone resorption), and serum bone-specific alkaline phosphatase (a marker of bone formation) by 50% to 55% and 25% to 30%, respectively, within 3 to 6 months after initiation of therapy.

Paget’s Disease

Paget’s disease of bone is a chronic, focal skeletal disorder characterized by greatly increased and disordered 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.

In pagetic patients treated with risedronate sodium tablets 30 mg daily for 2 months, bone turnover returned to normal in a majority of patients as evidenced by significant reductions in serum alkaline phosphatase (a marker of bone formation), and in urinary hydroxyproline/creatinine and deoxypyridinoline/creatinine (markers of bone resorption).

12.3 Pharmacokinetics

Absorption
Based on simultaneous modeling of serum and urine data, peak absorption after an oral dose is achieved at approximately 1 hour (Tmax ) and occurs throughout the upper gastrointestinal tract. The fraction of the dose absorbed is independent of dose over the range studied (single dose, from 2.5 mg to 30 mg; multiple dose, from 2.5 mg to 5 mg). Steady-state conditions in the serum are observed within 57 days of daily dosing. Mean absolute oral bioavailability of the 30 mg tablet is 0.63% (90% CI: 0.54% to 0.75%) and is comparable to a solution.

Food Effect
The extent of absorption of a 30 mg dose (three 10 mg tablets) when administered 0.5 hours before breakfast is reduced by 55% compared to dosing in the fasting state (no food or drink for 10 hours prior to or 4 hours after dosing). Dosing 1 hour prior to breakfast reduces the extent of absorption by 30% compared to dosing in the fasting state. Dosing either 0.5 hours prior to breakfast or 2 hours after dinner (evening meal) results in a similar extent of absorption. Risedronate sodium tablets are effective when administered at least 30 minutes before breakfast.

Distribution
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 [14 C] 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%.

Metabolism
There is no evidence of systemic metabolism of risedronate.

Excretion
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, 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: Risedronate sodium tablets are not indicated for use in pediatric patients [see Pediatric Use (8.4)].

Gender: Bioavailability and pharmacokinetics following oral administration are similar in men and women.

Geriatric: Bioavailability and disposition 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.

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. Risedronate sodium tablets are not recommended for use in patients with severe renal impairment (creatinine clearance less than 30 mL/min) because of lack of clinical experience. 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: No specific drug-drug interaction studies were performed. Risedronate is not metabolized and does not induce or inhibit hepatic microsomal drug-metabolizing enzymes (Cytochrome P450) [see Drug Interactions (7) ].

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