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Pharmacology (Winter) > Osteoporosis Drugs > Flashcards

Osteoporosis Drugs Flashcards

1
Q

Osteoporosis:

A

“Osteo” = Bones and “Porosis” = Porous

INCREASE likelihood of a fracture

“a pediatric disease w/ geriatric consequences”

  • Porous bones are weak and fracture easily.
  • A major cause of disability in the elderly.

breakdown/resorption > formation
= REDUCED bone density
–> fracture

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2
Q

What are Bone Cells?

A
  • OSTEOBLASTS secrete collagen matrix around themselves which calcifies
  • Type 1 collagen + Ca2+ + PO42- → hydroxyapatite crystal
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3
Q

Osteocyte:

A

maintains bone tissue

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4
Q

Osteoblast:

A

forms bone matrix

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5
Q

Osteogenic cell:

A

stem cell

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6
Q

Osteoclast:

A

resorbs bone

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7
Q

What is bone remodelling?

A

Bone turnover: 100% per year for infants, 20% in adults

balance b/t blasts & clasts constantly

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8
Q

Bone __________ & ___________ are normally balanced.

A

resorption

reformation

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9
Q

What is Excessive Osteoclastic activity?

A

Excessive Osteoclastic activity and the same level of Osteoblastic activity leads to osteoporosis.

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10
Q

What is the diagnosis of Osteoporosis?

A

X-RAY
* Fragility fractures from minor trauma- sneezing, coughing, bending, etc.

BONE MINERAL DENSITY
* Assessed by dual X-ray Absorptiometry at hip & spine.
* >50% decrease in density = osteoporosis
* T score < -2.5

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11
Q

What is the risk factors for osteoporosis?

A
  • Menopause (b/c no longer have monthly cycle of estrogen)
  • Age (>50 yrs old)
  • Drugs e.g. Glucocorticoids
  • Stress
  • Genetics
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12
Q

Parathyroid Hormone (PTH):

A
  • Maintains blood calcium

↓ EC Ca2+

↑ PTH secretion
1. ↑ Ca2+ & Phosphorus Secretion in Blood
2. ↑ Ca2+ Reabsorption
↑ Phosphorus Excretion in Urine Activates 1a-Hydroxylase
3. ↑ Ca2+ & Phosphorus Reabsorption

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13
Q

What is Parathyroid Hormone (PTH)?

A
  • Elevated PTH increases bone turnover and remodeling
  • ACTIVATES osteoblasts (bone formation increases)
  • But osteoblasts activate osteoclasts by induction of a membrane-bound protein ligand (RANKL)
  • Indirectly increases both the NUMBERS and ACTIVITY of osteoclasts
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14
Q

What does Calcitonin do?

A

Comes from the Thyroid gland - opposite of PTH (when Ca2+ levels get too HIGH in body, we have more Calcitonin produced & its goal is to try to REDUCE Ca2+ in blood)

  • Inhibits Ca2+ reabsorption in the kidney (excreted in the urine)
  • Promotes deposition of Ca2+ into bones (inhibits osteoclasts & stimulates osteoblasts)
  • Inhibits Ca2+ absorption by the intestines
  • Lowers Ca2+ levels in blood
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15
Q

What is Estrogen & Testosterone?

A
  • Sex hormones increase osteoblast activity, block osteoclast activation
  • This becomes an issue with aging, particularly after menopause in women
  • b/c don’t have estrogen needed to maintain bone
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16
Q

Glucocorticoids:

A
  1. ↓ Bone Formation
  2. ↓ Sex Hormone Secretion –>
    ↑ Bone Resorption
  3. ↓ Ca2+ Absorption & ↓ Renal Ca2+ Reabsorption
    –> ↓ Plasma Ca2+ –> ↑ PTH Secretion –> ↑ Remodeling

=> Osteoporosis

17
Q

What are strategies for preventing or delaying
osteoporosis?

A

Stronger bones at age 16 to 25 decrease degree of osteoporosis in later life.

  1. Weight bearing exercise
  2. Cessation of smoking, limiting alcohol intake
  3. Avoiding drugs that increase bone loss, e.g. Glucocorticoids
  4. Diet containing Calcium and Vitamin D
18
Q

What is Calcium?

A
  • ~ 99% of body’s calcium in bones and teeth; 1% in blood, muscle and other tissues
  • Age 18-50: 1000 mg/day
  • Age 50+: 1200 mg/day
  • 300 mg in each: 1 cup milk, 1 cup fortified orange juice, 3⁄4 cup yoghurt, cheese
  • Adequate calcium and vitamin D intake VERY IMPORTANT ADJUNT with OP meds
19
Q

What is Vitamin D?

A

Calcitriol (1, 25 OH-VIT D3) Bone Actions (systemically)
* ↑ Ca2+ and phosphate absorption from gut
* ↓ renal excretion of Ca2+ and phosphate
* ↑ bone turnover or remodeling (stimulates both bone formation and resorption)

  • Deficiency can be due to poor diet or inadequate sunlight
  • Age <50: 400-1000 IU/day
  • Age>50: 800-2000 IU/day
20
Q

What are strategies for managing osteoporosis?

A

Anti-resportives (prevent osteoclast activity)

21
Q

What is Bisphosphonates
(Alendronate, Risendronate, Zoledronic acid) MOA?

A
  • BIND DIRECTLY TO THE BONE (hydroxyapatite crystals)
  • Taken up by osteoclasts during remodeling

*Inhibit osteoclast activity and bone resorption by
inhibiting the cholesterol synthesis pathway (2nd, 3rd gen)
- kill osteoclasts

22
Q

What are the pharmacokinetics of Bisphosphonates?

A

Considered 1st line therapy for prevention and treatment of OP

23
Q

What is the absorption of Bisphosphonates?

A

low and variable; <1% of an oral dose is absorbed;

  • Must be taken first thing in a.m. with full glass of water only on empty stomach
  • Beverages (especially milk, coffee, orange juice, and mineral water) and food reduce absorption by up to 60%, do not consume for at LEAST 30 min after dose
  • Dairy-rich foods, antacids, calcium should ideally be taken 2 or 3 hours after med.
24
Q

What is the half-life elimination of Bisphosphonates?

A

Varies from months to years; slowly released with process of bone turnover
▪Eliminated by kidneys

25
Q

What is the dosing of Bisphosphonates?

A

Alendronate and risedronate once weekly; Zoledronic acid given intravenously once yearly

26
Q

What are the adverse effects of Bisphosphonates?

A

▪ALL bisphosphonates may cause bone, joint &/or muscle pain

▪Oral- may cause GI related problems such as abdominal pain, acid reflux, nausea, esophagitis, ulcers

▪I.V.-Acute-phase reaction; FLU-LIKE sx’s such as fatigue, fever, chills; usually occurs 3 to 7 days following the infusion; reaction tends to lessen with subsequent infusions.

▪RARE risks with long term use: osteonecrosis of the jaw (ONJ) and atypical femur fractures (AFF)

27
Q

What is Denosumab?

A
  • Monoclonal antibody
  • Prevents RANKL from binding to RANK receptor on osteoclasts in the circulation
  • Inhibits development, activation, and survival of osteoclasts
  • Dose: subcutaneously q 6 months
28
Q

What are the hormone related medication strategies for managing osteoporosis?

A
  • Teriparatide
  • Calcitonin
  • Estrogen (for post-menopausal women)
  • Raloxifene
29
Q

What is Teriparatide?

A
  • Recombinant formulation of part of parathyroid hormone
  • ANABOLIC ACTION: stimulates osteoblast activity (more than osteoclasts)
  • Net effect is increased bone formation
  • Indicated for SEVERE osteoporosis
  • Administered subcutaneously (DAILY)
  • Associated with an increased risk of cancer (osteocarcinoma)
  • Expensive!
30
Q

What is Calcitonin?

A

↓ osteoclastic bone resorption (↓ serum calcium)

  • Can be used to treat osteoporosis
  • Only WEAKLY BENEFICIAL (other drugs are better)
  • Increased risk of CANCER
31
Q

What is Estrogen (for post-menopausal women)?

A
  • Not recommended for treatment of OP, but may provide some benefit when menopause symptoms are also severe
  • Decreases bone resorption; reduces RANKL; increases OPG

Potential systemic effects:
* Increased risk of breast cancer with long term therapy; increased risk of stroke,

32
Q

What is Raloxifene?

A
  • Selective Estrogen Receptor Modulator
    (partial estrogen agonist-antagonist) for OP in post- menopausal women (better)
  • Agonist on bone; ANTAGONIST AT BREAST & ENDOMETRIUM
  • Decreases bone resorption, reduces RANKL
  • Associated with RISK REDUCTION IN BREAST CANCER (therefore, better than Estrogen option) in postmenopausal women
  • Other adverse events: hot flashes; leg cramps/muscle spasms, thrombosis (can increase risk of stroke)
33
Q

Denosumab?

A

RANKL inhibitor

34
Q

Raloxifene Estrogen?

A

reduce RANKL

35
Q

Teriparatide?

A

PTH Analog - for bone formation

36
Q

Calcitonin?

A

for reabsorption

37
Q

Bisphosphonates?

A

bind to bone inhibit osteoclasts

for resorption

Pharmacology (Winter) (23 decks)

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