Bone Mineral Homeostasis Flashcards
Vitamin D analogs and what do they treat
Calcipotriene – used to treat psoriasis
Paricalcitol – used to treat secondary hyperparathyroidism in patients with chronic kidney disease
Fibroblast growth factor 23 (FGF23)
Long polypeptide chain
Inhibits 1,25(OH)D3 production and phosphate reabsorption in the kidney
Produced in osteoblasts and osteocytes
Calcitonin naturally in the body does what?
Lowers serum calcium and phosphate levels
Acts on bone and kidney
Inhibits osteoclasts (blocks bone resorption)
Reduces calcium and phosphate reabsorption
What stimulates calcitonin secretion
Pentagastrin
Calcitonin is used to treat what?
Paget’s Dz
Hypercalcemia
Postmenopausal osteoporosis (sometimes)
Used off label for bone pain (cancer) and vertebral fracture
Calcitonin med MOA
Reduces the number of osteoclast and prevents resorptive activity of the bone: reduced bone turnover rate; temporary increase in osteoblastic activity.
*derived from salmon
Calcitonin Administration and Bio availability
Nasal spray or IV
BA of nasal = 3%
Calcitonin general recommendation for use
Recommended to use for short term (under 6 mos) or for use in bone pain (vertebral fracture/bone ca)
FDA warning for Calcitonin
Advisory Panel for FDA “benefit of calcitonin salmon products in treating…osteoporosis is outweighed by a potential increase in the risk of cancer.” (0.7% oral to 2.4% nasal)
Estrogens MOA and use
Prevent accelerated bone loss (postmenopausal)
Use for osteoporosis prophylaxis (increased vit D)
Estrogens ADE
endometrial/breast hyperplasia/cancer, MI, stroke, cancer, dementia, DVT
Glucocorticoids MOA
Antagonize vitamin D-stimulated intestinal calcium transport, stimulate renal calcium excretion, block bone formation.
Bisphosphonates Drugs
Alendronate (Fosamax)
Risedronate (Actonel),
Zoledronate (Zometa, Reclast)
Ibandronate (Boniva)
Bisphosphonates MOA
Osteoclast Inhibitors/osteoclast apoptosis
Bisphosphonates ADE
Esophagitis (oral) Do not use in Barrett’s esophagus
Risk of osteonecrosis of the jaw and subtrochanteric fractures- both are rare
Bisphosphonates drug admin instructions
Administer first thing in the morning on empty stomach with nothing but plain water, remain upright for 30 min.
Note: Food delays absorption (BA under 10% t ½ 10yrs)
May consider “drug holiday” after 5 years
Calcimimetics Name, MOA, and Use
Cinacalcet (Sensipar) – blocks PTH secretion in parathyroid gland – lowers serum Ca levels
Use for txt of secondary hyperparathyroidism (chronic kidney dz, cx), Hypercalcemia- parathyroid cx
Thiazides use
reduce renal calcium excretion
Fluoride
stabilizes hydroxyappatite crystal
Hypercalcemia Tx
Avoid aggravating factors: thiazide diuretics, lithium, volume depletion, inactivty, dietary Ca
Volume expansion- NS @ 200-300ml/hr
Bisphosphonates
(Pamidronate, zoledronate)
Calcitonin
Cinacalcet (Sensiar)
Plicamycin (Mithramycin)- Drug of last resort due to toxicity
Hypocalcemia causes
Caused by vit D def, CKD, malabsorption hypoparathyroidism. (neuromuscular sxs)
How to calculate corrected calcium
CC=0.8(4-albumin)+ serum Ca
Hyperphophatemia Preferred Drug and MOA
Sevelamer (Renagel, Renvela) titrate based on levels
800mg-1600mg TIDcc (BA=0%)
Inhibits intestinal absorption, lowers LDL and TC
What is a risk of using calcium supplements?
risk ectopic calcification
