corticosteroids Flashcards

1
Q

Glucocorticoids are produced where?

A

adrenal gland, adrenal cortex, zona fasiculata

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2
Q

biosynthesis of adrenal steroids

A
  • cholesterol is the common source from which all adrenal steroids are formed **
  • cortisol: one pathway of cortisol synthesis involves progesterone, one pathway from 17-hydroxyprogesterone
  • aldosterone: from progesterone
  • androgens: from 17-hydroxyprogesterone or 17-hydroxypregnenolone
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3
Q

double negative feedback loop regulation of corticosteroid release

A
  • hypothalamus releases CRF
  • CRF stimulates anterior pituitary to release ACTH into the bloodstream
  • ACTH stimulates the release of cortisol from the adrenal cortex
  • high blood levels of cortisol inhibits both (1) hypothalamus release of CRF and (2) ant. pituitary release of ACTH
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4
Q

circadian rhythm

A
  • the result of fluctuating levels of circulating cortisol caused by dbl negative feedback loop regulation
  • diurnal peak at about 8am daily, assuming hours of wakefulness from 6a-10p
  • affected by travel, sleep patterns, light cycle, exogenous cortisol intake, stress
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5
Q

effect of stress on adrenal steroids

A
  • causes release of catecholamines to maximize utilization of energy
  • causes release of glucocorticoids to maximize availability of energy
  • catecholamines and glucocorticoids work in concert
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6
Q

mechanism of action of glucocorticoids

A
  • ligand binds to receptor in the interior of the cell (widely distributed in the cytosol)
  • ligand/receptor complex moves into the nucleus and binds to DNA where protein production can be activated or inhibited
  • influence on DNA transcription of several proteins may take place simultaneously
  • this mechanism accounts for the slow onset of action of glucocorticoids
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7
Q

general effects of glucocorticoids (list of 10)

A
  • increases sensitivity to adrinergic drugs
  • direct vascular effects (from dyslipidemia and htn)
  • anti-inflammatory effects (decreased leukotriene and prostaglandin production, reduced macrophage recruitment); limits the damage associated with spinal cord injury due to inflammation
  • inhibits wound healing (inhibits fibrin, inhibits collagen deposition)
  • increased bone catabolism / brittle bone syndrome; antagonize effects of vitamin D on calcium absorption
  • required for production of surfactant (effect on fetal growth)
  • destruction of lymphocytes in lymph nodes
  • inhibits mitosis by transformed lymphoblasts
  • anabolic in the liver (leads to enlarged liver) / catabolic everywhere else
  • anti-insulin effects: increases glucose and fatty acid availability for energy (gluconeogenesis, glycogenesis, lipid breakdown to free fatty acids); overall: increased amino acids, fatty acids, glycerol delivery to liver for glucose/glycogen production
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8
Q

simplified arachidonic acid cascade

A
  • phospholipase A2 causes release of free arachidonic acid from cell membranes (this initial step is blocked by glucocorticoids)
  • 2 pathways for metabolism of free arachidonic acid: cyclooxygenase pathway, lipoxygenase pathway
  • lipoxygenase pathway: produces leukotrienes
  • cyclooxygenase pathway: produces prostaglandins and thromboxane A2 (this pathway blocked by NSAIDS this accounts for anti-inflammatory effects (less prostaglandins) and impaired clotting (less thromboxane A2))
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9
Q

inflammatory mediators

A
  • release is stimulated by prostaglandins
  • histamine, serotonin, bradykinin, substance P, lipid mediators
  • prostaglandins also cause change in pH of local tissue
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10
Q

lipid mediators (list)

A
prostaglandins
thromboxane A2
HETE
leukotrienes
platelet activating factor
activated complement components
lysosomal enzymes
autoantibodies
cytokines
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11
Q

prostaglandin D2

A
  • cyclooxygenase metabolite

- causes vasodilation, destabilization of basophils, hyperalgesia, *bronchoconstriction

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12
Q

prostaglandin E2

A
  • cyclooxygenase metabolite
  • causes vasodilation, increased vascular permeability (swelling), release of calcium from bone, hyperalgesia, *elevated body temp by action on hypothalamus, *maintain renal blood flow and sodium excretion during low flow (inhibiting causes serum hyperkalemia), *protection of GI tract mucosal layer
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13
Q

prostaglandin F2alpha

A
  • cyclooxygenase metabolite

- causes *bronchoconstriction, *dysmennorhea, *uterine contractions, hyperalgesia

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14
Q

prostaglandin I2

A
  • cyclooxygenase metabolite

- causes release of calcium from bone, vasodilation, *inhibits platelet aggregation

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15
Q

thromboxane A2

A
  • cyclooxygenase metabolite

- involved in regulation of platelet function

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16
Q

5-HETE

A
  • lipoxygenase metabolite

- causes chemotaxis

17
Q

leukotrienes B4

A
  • lipoxygenase metabolite

- causes chemotaxis

18
Q

leukotrienes C4,D4,E4

A
  • lipoxygenase metabolite

- causes vasoconstriction, bronchospasm, increased vascular permeability, neutrophil activation

19
Q

pharmacokinetics

A
  • 90% plasma bound: cortisol (Corticosteroid binding globulin, α2- globulin); synthetic corticosteroids (albumin)
  • competitive interaction with other plasma bound drugs, will increase serum levels of those drugs (i.e. warfarin, aspirin)
  • liver inactivation
20
Q

short-acting glucocorticoids

A

cortisone
hydrocortisone

  • plasma half life: 30-75 min
  • *biological half-life: 8-12 hrs
  • mineralocorticoid potency is 2x compared to anti-inflammatory potency
21
Q

intermediate-acting glucocorticoids

A

prednisone
prednisolone
triamcinilone
methylprednisolone

  • plasma half life: 1-4 hrs
  • *biological half life: 18-36 hrs
  • slight mineralocorticoid activity with prednisone, none with the rest
  • anti-inflammatory potency is 4-5x compared to short-acting
22
Q

long-acting glucocorticoids

A

dexamethasone
betamethasone

  • plasma half life: 2-5 hrs
  • *biological half life: 36-54 hrs
  • no mineralocorticoid activity
  • anti-inflammatory potency is 25x compared to short-acting

significant s/e of long-actings: disruption of circadian rhythms, no diurnal cortisol peak bc cortisol levels remain consistently high due to long half life

23
Q

therapeutic uses of glucocorticoids (8)

A
  • inflammatory diseases: eczema, dermatitis, arthritis, bursitis, inflammatory bowel disease
  • respiratory diseases: asthma, COPD
  • rheumatoid/collagen diseases: rheumatoid arthritis, lupus
  • immune suppression: autoimmune diseases, organ transplant, acute allergic conditions (bee sting, drug hypersensitivity, angioedema)
  • replacement therapy for Addison’s (cortisone)
  • cerebral edema (dexamethasone)
  • premature delivery (to increase surfactant; betamethasone)
  • inhibit fibrosis in eye injury
24
Q

adverse effects: adrenal suppression

A
  • adrenal cortex normally produces cortisol 30mg/day
  • if exogenous cortisol given for an acute process (not replacement therapy), the artificially high levels of cortisol influence dbl negative feedback loop
  • results in decrease of endogenous cortisol production if exogenous dose < 30 mg/day
  • results in cessation of endogenous cortisol production if exogenous dose > 30 mg/day
  • with abrupt discontinuation of exogenous dosing, the adrenal cortex will not have had time to respond, results in adrenal insufficiency
25
Q

adverse effects

A
  • immunosuppression (can be therapeutic or adverse depending on context)
  • fluid and electrolyte imbalance (due to mineralocorticoid activity of short-acting glucocorticoids)
  • peptic ulcer disease (suppression of PGE1); abdominal pain/burning, bloody/black stools
  • eye problems: with CHRONIC use only; sub capsular cataracts, increased intraocular pressure, eye redness, photophobia
  • CNS: psych sx due to loss of diurnal rhythm/ difficulty sleeping, unusual tiredness/weakness
26
Q

more adverse effects

A
  • osteoporosis/ brittle bone syndrome: decr bone formation, release of bone calcium, reduces protein matrix that bone builds on
  • aseptic necrosis (esp head of femur)
  • decreased wound healing (due to effects on collagen)
  • loss of muscle mass (breakdown protein to amino acids for glucose/glycogen production in liver); muscle cramps/weakness
  • increased circulating triglycerides (breakdown of adipose to free fatty acids for glucose/glycogen production in liver)
  • decreased carbohydrate tolerance (hyperglycemia)
  • redistribution of body fat (loss of body fat to hip and shoulder, truncal obesity, moon face, buffalo hump); rapid weight gain
27
Q

and even more adverse effects

A
  • dysmennorhea
  • pitting of skin at site of injection (must rotate sites with each injection)
  • unusual bruising (inhibition of thromboxane A2)
  • thin, fragile or shiny skin
  • hirsutism
28
Q

Cushing syndrome

A
  • over-administration of exogenous glucocorticoids
  • over-secretion of ACTH (pituitary over-secretion or ectopic secretion)
  • symptoms: acne, truncal obesity, moon face, buffalo hump, purple striae on abdomen, thin extremities
29
Q

Addison’s disease

A
  • auto-immune mediated adrenal insufficiency
  • symptoms: chronic fatigue, muscle weakness, loss of appetite
  • treatment: chronic replacement therapy (either intermediate acting glucocorticoid with alternating day therapy but trending toward short-acting/cortisol given every morning to minimize disruption of circadian rhythm)
30
Q

causes of adrenal insufficiency

A
  • primary adrenal insuff: Addison’s, tuberculosis, surgical removal adrenal gland(s)
  • secondary adrenal insuff: ACTH insuff, abrupt withdrawal of exogenous glucocorticoid therapy