Pharmacology of bone and calcium Flashcards
Osteodystrophy
Occurs in renal failure. Driven by secondary hyperparathyroidism.
Fragility fracture
Low trauma fracture.
Conservative prevention of osteoporosis
Maintain strong bones - diet, exercise
Early detection (DEXA)
Prevent fractures (mortality and morbidity)
Drug targets for Ca2+ homeostasis
Parathyroid glands
Kidney
Gut
Bones
Drugs used in calcium disorders
bisphosphonates
Calcium salts
Calcitonin
SERMs
Vitamin D
Indications for using calcium salts as therapy.
Used to replace calcium deficits. e.g. calcium deficiency, hypocalcaemia, osteoporosis
Given orally (IV in emergency). Causes mild GI disturbance.
Name 3 actions of vitamin D
Regulation of Ca2+/PO4 homeostasis
Maintencance of normal bone
Cell growth and division
Phamacological vitamin D
Can be adminstered as inactive form (cholecalciferol D3 or ergocalciferol D2) or active form (calcitriol)
Acts on the gut to absorb calcium from the diet.
Used in patiens with rickets/osteomalacia, kidney disease, hyperparathyroidism and renal osteodystrophy
May cause hypercalemia
Name 3 drugs used in prevention of osteoporosis
Bisphosphonates
SERMs
Parathyroid hormone
HRT
Calcitonin
Strontium Ranelate
Mechanism of action of calcitonin
Binds receptors on osteoclasts which inhibits their mobilisation of bone, and acts on the kidney to limit calcium reabsorption from the proximal tubules.
used in hypercalcaemia, osteoporosis, Pagets disease or neoplastic disease
SERMs in osteoporosis
SERMs act on oestrogen receptors
Raloxifene is bone specific. It acts as an agonist in bone and lipid metabolism, but antagonises receptors in the endometrium and breast.
Used for the prevention of post-menopausal osteoporosis
Mechanism of action of bisphosphonates
Inhibit bone resorption.
Form complexes with calcium in the bone matrix and area absorbed onto hypoxyapatite crystals.
Released when OC-mediated bone resorption occurs and inhibit metabolism of OCs or accumulate and promote apoptosis.
Used in osteoporosis, malignant disese of bone (reduces damage, pain and hypercalcaemia), Paget’s disease.
Absorption is impaired by food (particurly Ca2+) so must be taken on an empty stomach. Excreted renally and can cause insufficiency. Also cause Gi disturbance
Strontium ranelate
Inhibits bone resorption and stimulates bone formation. Absorbed into hydroxyapatite. Mechanism unclear.
Drugs used in gout
Allopurinol: reduces uric acid synthesis. Used as long term treatment.
Colcicine: inhibits migration of neutrophils to the joint. Can relieve and prevent an acute attack. Causes GI disturbance
NSAIDs (not aspirin) reduce plasma urate levels by inhibiting uric acid secretion.
