Bone Loss

 

ACR: Fosamax Prevents Loss Of Bone Mass Following Hip 
Doctor's Guide November 15, 1999

BOSTON, MA -- November 15, 1999 -- Fosamax(R) (alendronate sodium) in investigational use prevented the early loss of bone mass that often occurs in patients following hip replacement surgery. The two-year study, presented at the annual meeting of the American College of Rheumatology, is the first study of a medicine for the prevention of bone loss in this population.

Approximately 300,000 hip replacement surgeries are performed in the United States each year. The surgical procedure, called hip arthroplasty, involves removing parts of the hip joint that have been destroyed by injury or disease such as arthritis and replacing the joint with an artificial implant or prosthesis.

Because hip replacement surgery causes a redistribution of load or stress to the bone around the implant (known as stress shielding), rapid bone loss frequently occurs following surgery. Furthermore, years after the surgery additional bone destruction around the implant may occur due to osteolysis, an inflammatory reaction to the debris particles generated by wear and tear on the artificial hip joint, and may eventually lead to loosening of the hip joint or pain in the hip. Loosening of the hip prosthesis is a significant complication that can lead to an increased risk of fracture and is the leading cause for surgery to replace hip implants (revision surgery). Revision surgery is technically demanding and costly with lower rates of success than primary hip replacement and higher rates of complications.

"Our goal is to help prevent the complications of hip prostheses, such as loosening, and the need for revision surgeries by preserving bone mass with drug therapy," said Dr. Albert Leung, associate director, Endocrine and Metabolism Clinical Research, Merck Research Laboratories. "In this study, initiation of therapy with Fosamax immediately following hip replacement surgery maintained, or even increased, the patients' bone mass above pre-surgery levels. The impact that this will have on the need for future revision surgeries is yet to be determined."

The data on Fosamax are two-year results from a double-blind, single- center, placebo-controlled, randomized trial performed by the late Anthony Lyons, Faculty Royal College of Surgeons (FRCS) and Brigitte Scammell, FRCS, Department of Orthopaedic & Accident Surgery, Queen's Medical Centre and University Hospital, Nottingham, U.K. The study was sponsored by Merck & Co., Inc.

In the first year of this investigational study, 49 patients between 46 and 81 years of age with cemented Charnley Total Hip Arthroplasty were divided into three patient groups:

-- "acute" patients with a recent hip replacement within 30 days of entering the study (n=16)

-- "chronic" patients with hip replacement surgery performed more than five years prior to the study with no evidence of loosening of the implant (n=17)

-- "revision" patients with hip replacement surgery performed more than five years ago and loosening of their implant. These patients were enrolled in the study while awaiting revision surgery to replace the loose implant (n=16).

Patients were randomized to receive either Fosamax (10 mg once daily) or placebo. All patients were supplemented with 500 mg elemental calcium daily. Bone mineral density was measured by dual-energy x-ray absorptiometry (DXA) using special software to study the region around the hip implant.

In the second year of the study, 13 patients from the acute group (seven treated with Fosamax and six placebo) and 13 from the chronic group (six treated with Fosamax and seven placebo) were continued on the same treatment as in year one. Revision patients from the first year of the study were not continued in year two.

At the end of two years of treatment, pooled data for the acute and chronic groups showed patients treated with Fosamax had a mean increase in bone mineral density relative to baseline of 1.4 plus or minus 0.76 percent versus a mean decrease relative to baseline in the placebo group of 0.4 plus or minus 1.75 percent. The estimated mean difference between patients treated with Fosamax and patients treated with placebo was 2.30 percent (p=0.18).

-- Confirming earlier findings from the first year of the study, there was a significant treatment effect seen in the acute treatment group. Patients treated with Fosamax in the acute group had a 0.8 plus or minus 1.06 percent gain in bone mineral density from baseline vs. a loss of 4.78 plus or minus 0.47 percent from baseline in the patients treated with placebo. The mean difference between the patients treated with Fosamax and patients treated with placebo was 5.58 percent (p<0.001) at month 24.

-- In the chronic group the difference in bone mineral density around the hip implant was not significantly different between the patients treated with Fosamax and those treated with placebo.

"These results showed that it may be more beneficial to begin treatment with Fosamax soon after hip replacement surgery in order to prevent loss of bone mass," said Dr. Leung.

A non-hormonal, bone-specific therapy, Fosamax has been studied in more than 17,000 patients in randomized clinical trials to advance the understanding of the prevention and treatment of osteoporosis. This study of Fosamax in investigational use for periprosthetic bone loss continues the extensive clinical trial program to explore new uses for the drug.

Fosamax was approved in the United States by the Food and Drug Administration in 1995 for the treatment of osteoporosis in postmenopausal women (10 mg once daily) and for treatment of Paget's disease of bone (40 mg once daily). In 1997, Fosamax (5 mg once daily) was approved for the prevention of osteoporosis in postmenopausal women at risk of osteoporosis, and Fosamax (10 mg once daily) was approved for the prevention of fractures in postmenopausal women who have osteoporosis. In June 1999, Fosamax was approved as the first medication for treatment of glucocorticoid-induced osteoporosis in men and women receiving glucocorticoids (commonly referred to as corticosteroids or steroids) in a daily dosage equivalent to 7.5 mg or greater of prednisone and who have low bone mineral density.

Like other drugs in the same class, known as bisphosphonates, Fosamax should be used with caution in people with certain stomach or digestive problems. Fosamax should not be used if the patient has certain disorders of the esophagus (the tube that connects the mouth with the stomach) that delay emptying or if the patient is unable to stand or sit upright for at least 30 minutes. In addition, Fosamax should not be used in patients with severe kidney disease or low levels of calcium in their blood, in patients who are allergic to Fosamax or in patients who are pregnant or nursing.

Some patients may develop severe digestive reactions including irritation, inflammation or ulceration of the esophagus. (See prescribing information for more details.) Patients who experience heartburn, difficulty or pain when swallowing or chest pain should stop taking the drug and consult their doctor.

Like all prescription drugs, Fosamax may cause side effects. Side effects usually have been mild and generally have not caused patients to stop taking Fosamax.

Related Links: Fosamax(R) (alendronate sodium) and Merck & Co.

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