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Osteoporosis (Teriparatide
-Anabolic agent that increases bone formation.…
Osteoporosis
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Bisphosphonates
-Antiresorptive agent.
-Enzyme-resistant analogues of pyrophosphate, a normal constituent of tissue fluids that accumulates in bone and has a role in regulating bone resorption.
-Forms tight complexes with calcium in the bone matrix, and are released slowly as bone is resorbed.
Simple Compounds
-Similar to pyrophosphate
-Etidronate
-Incorporated into ATP analogues that accumulate within osteoclasts and promote apoptosis.
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Nitrogen-containing
-Prevent bone resorption by interfering with the anchoring of cell surface proteins to the osteoclast membrane.
-Alendronate, zoledronate
Given Orally (poorly absorbed).
50% of a dose accumulates at sites of bone mineralisation.
Free drug excreted by the kidney
ADR: GI, peptic ulcers, esophagitis, bone pain, osteonecrosis of the jaw
Vit. D (Colecalciferol, calcitriol)
All preparations can be given orally (well absorbed).
Fat soluble (bile salts necessary for absorption).
Excessive intake may cause kidney stones.
In clinical deficiency, administration of vitamin D restores bone formation
Given orally, well absorbed and fat soluble.
Increases calcium absorption in the intestine and decreases excretion.
Helps to mobilise calcium fro the bones.
Calcitonin
Given SC or IM or intranasally.
Action lasts several hours.
ADRs: N&V, facial flush, tingling sensation of the hands, unpleasant taste in the mouth.
A peptide hormone secreted by C-cells in the thyroid.
Inhibits bone resorption through binding to a specific receptor on osteoclasts, inhibiting their action.
In the kidney → decreases reabsorption of calcium and phosphate in the proximal tubules.
Overall effect: To decrease the plasma concentration.
HRT and SERMS s
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Raloxifene stimulates osteoblasts and inhibits osteoclasts.
Agonist actions on the cardiovascular system.
Antagonist action on mammary tissue.
Well absorbed in the GI
Extensive metabolism (low bioavailability)
ADRs: Hot flushes, leg cramps, flu-like symptoms, peripheral oedema.
Parathyroid hormone
Mobilises calcium from the bone.
Promotes resorption by the kidney.
Stimulates synthesis of calcitriol (increases calcium absorption from the intestine).
Promotes phosphate excretion, net effect to increase calcium in the plasma and lower phosphate.
Calcium
Calcium gluconate (po, IV)
Calcium lactate (po)
IV causes local necrosis.
Calcium carbonate poorly absorbed in the gut (used to treat hyperphosphatemia).
Also an antacid.
ADRs: GI disturbance
Estrogen
Inhibits cytokines that recruit osteoclasts and oppose the bone-resorbing, calcium mobilizing action of PTH.
Increase osteoblast proliferation, augment the production of TGF-beta and inhibit apoptosis.
Decrease of estrogen (menopause) can lead to osteoporosis
Glucocorticoids
Excessive concentration inhibit osteoclast differentiation and activity, and may stimulate osteoclast action → osteoporosis (e.g. Cushing's syndrome).
Thyroxine
Stimulates osteoclast action, reducing bone density and liberating calcium. Osteoporosis occurs in association with thyrotoxocosis (care during treatment of hypothyroidism).
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Monitored via DEXA (dual energy X-ray absorptiometry). This enables the definition of the degree of bone thinning.