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Risedronate is an osteoporosis medication, proven to reduce the
risk of bone fractures in elderly patients, and used widely by
doctors to treat osteoporosis and osteopenia.
Risedronate hit the market in 1997 as a third-generation bisphosphate. It was
developed by Proctor and Gamble and Sanofi-Aventis Pharmaceutical
company and now under Warner Chilcott. Risedronate is indicated
for treatment and prevention of postmenopausal woman with osteoporosis
by reducing the risk of bone fractures. A second indication is
in men with osteoporosis to increase bone mass. The third indication
is the treatment and prevention in men and women who are being
treated with glucocorticoids such as prednisone or similar products
for chronic diseases. These patients should also receive additional
amounts of calcium and vitamin D to prevent bone loss. The fourth
indication is for the treatment of Paget's Disease of both men
and women.
The bisphosphonate drugs, of which risedronate is one, have become
the mainstay medicine in attempts to forstall the progress of
osteoporosis in post menopausal women, and in other patients with
thinning bones. Risedronate has been found to reduce the incidence
of non-vertebral and hip fractures as well as breaks in the vertebrae
bones.
To understand the way risedronate acts on the bones, it is important
to understand the composition
and structure of bone. Bone composition is connective tissue
that becomes mineralized. Bone is composed of three components:
protein matrix, a mineral phase and bone cells. Osteonectin
is a protein found only in bone that binds to hydroxyapatite
crystals and bone collagen. The bone cell consist of primary three
types of cells, osteoblasts, osteocytes and osteoclasts.
Osteoblasts
are the cells that control the mineralization and produce the
bone matrix. Osteocytes are connected to each other by cytoplasm
extensions. This allows controls the rate of ions transported
into and out of the bone and regulate the mineralization of new
bone matrix. Risedronate works on the orthoclast cellular level.
Osteoclasts are large cells found on the resorbing surface of
mineralized bone. Osteoclasts primary responsibility is removal
of bone matrix. Risedronate works by acting as an antiresorptive
agent. At the cellular level risedronate inhibits osteoclasts.
The osteoclasts attach normally to the bone surface. This reduces
the active bone resorption, and prevents bone loss by reducing
bone turn over and bone resorption. Biochemical studies suggest
the drug "up-regulates" the cyclooxygenase 2 enzyme
and this contributes to the bone building.
Although risedronate is not routinely used in treatment of cancer,
recent research shows it
can be effective in treatment of a bone cancer called osteosarcoma.
Global sales of Risedronate are over 1 billon dollars annually.
Indeed, risedronate was the fastest Proctor and Gamble drug to
reach the $1 billion mark. The company spent 80 million dollars
on marketing in one year. Alendronate, marketed as Fosamax and
as a generic, holds 50% of the bisphosphonate market. Risedronate
ranks second holding 25% of the market.
Thin Bones
Although estrogen is commonly thought of as a woman’s hormone, it is present in men’s bodies as well and plays a part in the onset of at least some osteoporosis cases. It has been found that men with a deficiency of aromatase, the enzyme that converts testosterone to estrogen, have a higher tendency to develop osteoporosis. Giving these men estrogen supplements results in an increase in bone mass. Testosterone injections can result in an increase in bone mass, but only in men with sufficient serum estrogen levels.
Androgen deficiency also increases the risk of osteoporosis in both men and women. Androgen levels decline with age.
Approximately 1.5 million bone fractures occur every year in the US as a result of osteoporosis. Almost half of these are vertebrae (spinal) fractures, resulting in pain and disability. Wrist and hip fractures due to osteopenia are also common.
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