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Drugs affecting Bone Homeostasis
IL - Block 6 - Dr. Williams
27
Pharmacology
Professional
04/08/2012

Additional Pharmacology Flashcards

 


 

Cards

Term
what are the primary regulators of calcium and phosphate homeostasis?
Definition

PTH and vitamin D

 

calcitonin, glucocorticoids, and estrogens play secondary roles

Term
parathyroid hormone
Definition

acts on membrane G-protein-coupled receptors to increase cAMP in bone and renal tubular cells

 

in kidney: inhibits excretion of Ca2+, promotes PO4 excretion; stimulates production of active vitamin D metabolites

 

in bone: promotes bone turnover by increasing activity of osteoclasts and osteoblasts (osteoclast indirectly activated by PTH via osteoblast formation of RANK ligand (RANKL) - part of TNF cytokine family)

 

Term
PTH at continuously high levels (such as secondary hyperparathyroidism)
Definition
leads to increased bone resporption, hypercalcemia (initially), and hyperphosphatemia
Term
low intermittent doses of PTH produce . . .
Definition
a net increase in bone formation - basis of use of teriparatide, a recombinant truncated form of PTH, for IV tx of osteoporosis
Term
regulation of PTH
Definition

 

 

synthesis and secretion of PTH is primarily regulated by the serum concentration of free ionized calcium - drop in free ionized calcium stimulates PTH release

 

secondary Vitamin D metabolites play secondary role --> inhibit PTH synthesis

Term
teriparatide
Definition

recombinate truncated form of PTH

 

given IV for tx of osteoporosis

Term
Vitamin D
Definition
  • - fat soluble vitamin
  • - active metabolites are formed in the liver and kidney:

 

* 25-hydroxyvitamin D

* calcifediol

* 1,25-dihydroxyvitamin D (calcitriol)

 

  • - Renal synthesis of active metabolites of Vit D stimulated by PTH and FGF23 (produced by osteoclasts and osteoblasts)
  • active Vit D metabolites cause net increase in serum concentrations of calcium and phosphate by increasing intestinal absorption and bone resorption and decreasing renal excretion
  • inhibits PTH secretion DIRECTLY and INDIRECTLY (by increasing serum Ca)

 

-

Term
where does Vit. D have a greater effect: kidney or GI tract?
Definition
greater effect on GI tract and bone than kidney
Term
Vitamin D deficiency?
Definition

Vit D required for normal bone mineralization

 

= Ricket's in kids

 

= osteomalacia in adults

Term
what is Vitamin D used to treat?
Definition

deficiency states

intstinal osteodystrophy

chronic kidney or liver dz

hypoparathyroidism

nephrotic syndrome

 

also used in combination with calcium supplementation (prevent and treat osteoporosis in older women)

 

topical formation for psoriasis

 

 

Term
cholecalciferol and ergocalciferol
Definition

2 forms of Vitamin D

 

available as oral supplements

 

commonly added to dairy products and other foods

Term
calcitrol
Definition

active form of Vitamin D

 

required in patients with conditions that impair vitamin D activation (chronic kidney dz, liver dz, hypoparathyroidism)

 

in chronic kidney dz, calcitriol reduces PTH levels, corrects hypocalcemia, and improves bone disease, but it can also result in hypercalcemia and hypercaliuria through direct effects on intestinal, bone, and renal handling of calcium and phosphate

Term
doxercalciferol
Definition

prodrug that is converted in the liver to 1,25-dihyrdroxyvitain D

 

causes less hypercalcemia and less hypercalciuria than calcitriol

 

used in tx of secondary hyperparathyroism due to chronic renal dz

Term
paricalcitol
Definition

19-nor-1,25-dihydroxyvitamin D2

 

analog of calcitriol

 

causes less hypercalcemia and less hypercalciuria than calcitriol

 

approved for tx of 2ary hyperparathyroidism due to chronic renal dz

Term
calcipotriene
Definition

analog of calcitriol

 

causes less hypercalcemia and less hypercalciuria than calcitriol

 

used for tx of psoriasis

Term
toxicity of Vitamin D or its active metabolites
Definition

hypercalcemia

 

hyperphosphatemia

 

hypercalciuria

Term
calcitonin
Definition

secreted by the thyroid gland

 

decreases serum calcium and phosphate by inhibiting bone resorption and inhibiting renal excretion of these minerals

 

bone formation is ultimately reduced

 

USE: in conditions where an actue reduction of serum calcium is needed (ex: Paget's dz and hypercalcemia)

 

also approved for tx of osteoporosis (but not as effective)

 

salmon calcitonin used because has longer half-life and greater potency

 

admin = injection or nasal spray

Term
raloxifene
Definition

selective estrogen receptor modulators (SERMs)

 

prevent or delay bone loss in postmenopausal women

 

inhibition of PTH-stimulated bone resorption

Term
glucocorticoids
Definition

inhibit bone mineral maintenance = chronic systemic use is common cause of osteoporosis in adults

 

but they are useful in intermediate-term tx of hypercalcemia

Term
bisphosphonates
Definition

(alendronate, etidronate, ibandronate, pamidronate, risedronate, tiludronate, and zoledronic acid)

 

short-chain organic polyphosphate compounds that reduce both the resorption and the formation of bone by an action on the baasic hydroxyapatite crystal structure

 

effects on vit. D production and calcium absorptions from GI tract

 

direct effects on osteoclasts

 

used to manage hyper calcemia associated with some malignancies and to treat Paget's dz

 

chronic uses of this for osteoporosis tx (increases bone density and reduces fractures)

Term
cinacalcet
Definition

calcimimetics

 

 

lowers PTH by activating the calcium-sensing receptor in parathyroid gland

 

oral tx for secondary hyperparathyroidism in chronic kidney dz

 

tx for hypercalcemia in pts with parathyroid carcinoma -

 

toxicities include hypocalcemia and adynamic bone dz (profound decr. bone cell activity)

Term
which diuretics affect serum and urinary calcium levels
Definition
thiazide diuretics and furosemide
Term
1,25-dihydroxyvitamin D3 would do what on intesinal absorption of Ca and PO4-???
Definition
would increase absorption of both
Term
what would you give to a man with calcium-containing renal stones: Lasix or HCTZ?
Definition
hydrochlorothiazide (HCTZ)
Term
where does cinacalcet act to decr. PTH secretion?
Definition
acts by activating calcium-sensing receptors
Term
densoumab
Definition
decreases bone resorption by binding RANKL and preventing its effects on osteoclasts/osteoclas precursors
Term
alendronate is an analog of what?
Definition
pyrophosphate
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