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HRT
- anti-resorptive (anti-catabolic).
- considered for tx of mod-severe vasomotor symptoms of postmenopause only
- osteoporosis prevention is a secondary benefit
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Etidronate
- first-gen bisphosphonate, least potent anti-resorptive(anti-catabolic). R1 -CH3, R2 -OH
- Incorporates into bone, released when hydroxyapatite dissolved by osteoclasts
- Preferentially taken up by osteoclasts -> impair recruitment, differentiation, activity of osteoclasts. Increase osteoclast apoptosis.
- Dose that inhibits bone resorption also impairs bone mineralization --> osteomalacia.
- Therefore give: 400mg etid x14d, then 500mg CaCO3 x76d.
- 1o px post-men: no effect
- 2o px post-men: 50% RR vertebral fracture. NSS for non-vert, hip, wrist.
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Alendronate
- 2nd gen bisphosphonate. anti-resorptive (anti-catabolic). R1 -OH, R2 -CH2CH2CH2NH2
- Incorporates into bone, released when hydroxyapatite dissolved by osteoclasts
- Preferentially taken up by osteoclasts -> impair recruitment, differentiation, activity of osteoclasts. Increase osteoclast apoptosis.
- 1o px: 45% RR vertebral fracture (vs. NOT risedronate, and zolen was not tested)
- 2o px: 50% RR in vert, non-vert, hip fx (all 3 drugs)
- Orally, poorly absorbed (1-5%). Empty stomach, water only. t1/2 is 1 hour in plasma, 10 years in bone.
- 10mg/d or 70mg/week
-
Risedronate:
- 2nd gen bisphosphonate. anti-resorptive (anti-catabolic). R1 -OH, R2 -CH2N-ring.
- Incorporates into bone, released when hydroxyapatite dissolved by osteoclasts
- Preferentially taken up by osteoclasts -> impair recruitment, differentiation, activity of osteoclasts. Increase osteoclast apoptosis.
- 1o px: no effect
- 2o px: 50% RR in vert, non-vert, hip fx (all 3 drugs)
- Orally, poorly absorbed (1-5%). Empty stomach, water only. t1/2 is 1 hour in plasma, 10 years in bone.
- 5mg/d, or 35mg/week, or 75mg/day x2 days/month.
-
Zoledronate:
- 3rd gen bisphosphonate. anti-resorptive (anti-catabolic). R1 -OH, R2 CH2N-ring.
- Incorporates into bone, released when hydroxyapatite dissolved by osteoclasts
- Preferentially taken up by osteoclasts -> impair recruitment, differentiation, activity of osteoclasts. Increase osteoclast apoptosis.
- 1o px: not tested
- 2o px: 50% RR in vert, non-vert, hip fx (all 3 drugs)
- Injected 5mg once/year by IV infusion.
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Calcitonin
- peptide hormone in calcium homeostasis; decreases Plasma Calcium. Anti-resorptive (anti-catabolic).
- Suppresses activity of osteoclasts, decreases bone resorption.
- 30% RR in vertebral fx, but not non-vertebral.
- May have analgesic effect.
- 2nd line tx for post-men osteo, 1st line tx for pain ass'd with acute vert fx.
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Denosumab (prolia)
- osteoporosis anti-resorptive (anti-catabolic)
- monoclonal Ab to RANKL that mimcs action of OPG, prevents RANKL from binding to RANK.
- Decrease in osteoclast formation and bone resorption.
- Px severe osteoporosis in post-men: 60% RR vertebral, 20% RR non-vertebral, 40% RR hip
- May also be useful in conditions characterized by temporary rapid bone resorp (i.e. aromatase inhib tx)
- Injection: 60mg SC q6mo.
-
Teriparatide
- recombinante human PTH.
- Increases recruitment and differentioatn of osteoblasts and decreases apoptosis.
- Given intermittently, get net bone forming effect: increases bone remodeling, with anabolic window: initial stimulation of bone formation before resorption takes place. Window lasts 12-18 months.
- 2o post-men: 65% RR vert, 53% RR non-vert. No sig decrease in hip fx.
- Also for glucocorticoid-induced osteo in high-risk pts.
- Tx duration limited 2 years.Once daily injections.
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