Pharm (lecture focused) Flashcards
Abbreviations used in this section
SE = side effect
Rx = treatment
Corticosteroids - What is the drug that most mimics physiological cortisol?
Hydrocortisone (duration of action: 8-12 hours)
Corticosteroids - What is the drug with the strongest potency?
Dexamethasone (about 25-30x stronger)
Also lasts 3-6x longer (duration of action 36-72 hours)
No mineralocorticoid activity
Corticosteroids - what drug(s) has(have) no mineralocorticoid activity?
Dexamethasone (30x stronger than cortisol)
Triamcinolone (5x stronger)
Corticosteroids - which is used as a replacement for aldosterone?
Fludrocortisone - it has corticosteroid activity, but has much higher affinity for the mineralocorticoid receptors
If you wanted to give a patient something that isn’t as strong as dexamethasone but lasted longer than cortisol, which drug would you use?
Prednisone or prednisolone or any of its derivatives.
They have 4-5x more potency than cortisol and last 12-36 hours (compared to the 8-12 from cortisol and the 36-72 from dexamethasone)
What is an adrenal crisis? Symptoms? What is used to treat it?
Adrenal crisis aka acute adrenal insufficiency
- volume depletion and hypotension (due to combination of loss of aldosterone –> loss of volume and loss of vascular tone due to lack of cortisol)
- hyperkalemia (loss of aldosterone activity)
- hyponatremia (mineralocorticoid deficiency and increased ADH caused by cortisol deficiency)
Treatment
- Do NOT delay while waiting for definitive proof of diagnosis
- Treat with high-dose IV glucocorticoids (ie dexamethasone if no previous dx of adrenal insufficiency)
- Add hydrocortisone until patient stable
- gradual taper to a maintenance dose
Why is hyponatremia seen in adrenal crisis?
Due to 2 reason
- mineralocorticoid deficiency –> loss of Na+ in the tubules
- increased ADH (cortisol has negative feedback on the pituitary secretion of ADH, w/o cortisol –> increased ADH) –> increased volume diluting the low concentration of Na+ –> hyponatremia
Treatment for chronic adrenal insufficiency
Goal is “physiologic” replacement of glucocorticoids and mineralocorticoids
- hydrocortisone (15-20mg) on awakening and 5-10 mg in early afternoon
- fludrocortisone (0.05-0.2mg) orally daily
- liberal salt intake (remember there will be an excessive loss of salts)
“stress-dosing” is needed when a patient is ill
“stress-dosing” situations in patients with adrenal insufficiency
Illness (minor vs major)
emergency treatment of severe stress or trauma
surgeries
21-hydroxylase deficiency treatment
Steroids - usually dexamethasone, prednisone or hydrocortisone
In salt wasting, need fludrocortisone as well
Treat whatever degree of glucocorticoid and mineralocorticoid deficiency exists
Pharmacological treatment of Cushing’s syndrome (6)
- Aminoglutethimide - blocks conversion of cholesterol or pregnenolone (via enzyme P450scc = side chain cleavage)
- Ketoconazole - nonselective inhibitor of adrenal and gonadal steroid synthesis
- Mitotane - nonselective cytotoxic action on adrenal cortex. Bad SE profile
- Metyrapone - relatively selective inhibitor of 11-hydroxylation
- Mifepristone - progesterone receptor antagonist that has glucocorticoid receptor antagonist activity at higher concentration
- Pasireotide - somatostatin analog (blocks release of ACTH from the corticotropes)
Aminoglutethimide
blocks conversion of cholesterol or pregnenolone (via enzyme P450scc aka desmolase)
scc = side chain cleavage
Ketoconazole
nonselective inhibitor of adrenal and gonadal steroid synthesis
most commonly used until recently discovered SE of hepatotoxicity
Mitotane
nonselective cytotoxic action on adrenal cortex.
- toxic to adrenal cells
- most commonly used in adrenal carcinomas where you want to kill a section
Bad SE profile
Metyrapone
relatively selective inhibitor of 11-hydroxylation
Used in to treat and for diagnostic purposes
- If used, should decrease cortisol and corticosterone which should cause a compensatory rise in ACTH
- should also cause an increase in 11-deoxycortisol
Mifepristone
progesterone receptor antagonist that has glucocorticoid receptor antagonist activity at higher concentrations
- More than 3x the binding affinity for the GC receptor than dexamethasone
- no mineralocorticoid activity
Rx:
- to control hyperglycemia secondary to hypercortisolism who have failed or are not cadidates for surgery
- also useful for rapid treatment of cortisol-induced psychosis
SE:
- fatigue
- nausea
- headache
- hypokalemia
- arthralgias
- endometrial thickening in women
- creates generalized glucocorticoid resistance
Pasireotide
Somatostatin analog (agonist) aka GH-inhibiting hormone has a variety of functions:
- Suppresses the release of GI hormone (gastrin, CCK, secretin, motilin, VIP, GIP, enteroglucagon)
- Decreases rate of gastric emptying
- Suppresses the release of pancreatic hormones (inhibits insulin and glucagon release)
- suppresses the exocrine secretory action of pancreas
- blocks release of ACTH from corticotropes via high affinity somatostatin receptor subtype 5
SE:
- hyperglycemia (loss of insulin as stated above)
- GI symptoms (due to suppression of all the GI hormones and delayed gastric emptying)
Function of somatostatin
Suppresses the release of GI hormone (gastrin, CCK, secretin, motilin, VIP, GIP, enteroglucagon)
Decreases rate of gastric emptying
Suppresses the release of pancreatic hormones (inhibits insulin and glucagon release)
suppresses the exocrine secretory action of pancreas
What somatostatin analog is used in treatment of GH adenomas?
Octreotide
SE profile pretty much the same (GI symptoms and hyperglycemia)
Treatment for primary aldosteronism
Surgery
ADH antagonists – spironolactone (has anti-androgenic activity) and eplerenone
Toxicity of corticosteroids
- Insomnia (cortisol usually spike when you wake up and lowest when you sleep. Because its so high, it’s hard to sleep. The lack of sleep ultimately turns into mania resulting in behaviorial symptoms)
- Behaviorial changes (hypomania, acute psychosis)
- acute peptic ulcers (corticosteroids are known to inhibit the biosynthesis of gastric cytoprotective prostaglandins, while suppressing the production of gastric damaging leukotrienes.)
- acute pancreatitis (increased glucose as well as triglycerides mobilization by cortisol can cause excess secretion from the pancreas which increases the likelihood of inflammation)
- all the symptoms associated with Cushings
Why are corticosteroids associated with insomnia? behaviorial changes?
Cortisol usually spikes when you wake up and lowest when you sleep.
Because its so high, it’s hard to sleep. The lack of sleep ultimately turns into mania resulting in behaviorial symptoms
Why are corticosteroids associated with acute peptic ulcers?
corticosteroids are known to inhibit the biosynthesis of gastric cytoprotective prostaglandins
Why are corticosteroids associated with acute pancreatitis?
increased glucose as well as triglycerides mobilization by cortisol can cause excess secretion from the pancreas which increases the likelihood of inflammation
Steps in the synthesis of thyroid hormones
What enzyme(s) catalyze these reactions? Where do these reactions take place?
- (cytoplasm) Trapping (active uptake of iodine via the Na/I+ symporter)
- (cytoplasm) Oxidation of Iodide to iodine (activation)
- (colloid of follicle) Organification (iodide is converted to iodine and then condensed onto tyrosine residues on the polypeptide backbone of thyroglobulin – results in MIT or DIT)
- (colloid of follicle) Coupling (MIT+DIT or DIT+DIT forming T3 or T4)
- (cytoplasm) T3/T4 endocytosed and combined with a lysosome.
- (cytoplasm) Lysosomal enzymes cleave T4 and T3 from thyroglobulin colloid and hormones diffuse from follicle cell into bloodstream.
All the enzymatic reactions are catalyzed by thyroid peroxidase (oxidation, iodination/organification and coupling)!!
What role does thyroid hormone have in embyrological and child development?
Associated with skeletal and neural development via an important role in regulating the expression of genes
- Lack of thyroid hormone will result in short stature and mental status changes (ie retardation, etc…)
Also associated to a lesser degree with liver and heart development,
Synthetic T4
Levothyroxine
Synthetic T3
Liothyronine
What is the preferred thyroid hormone replacement? Why?
T4 (levothyroxine)
Lasts longer. Also avoids the majority of the hyperthyroid effect that may be present if giving T3
Chronic fatigue syndrome
What is it? Treatment?
Trouble converting T4 –> T3
Treat with T3 supplements
Treatment modalities for hyperthyroidism (5)
- Beta blockers (ie propranolol)
- thioamides (PTU, methimazole)
- I131 (irradiate thyroid gland via beta irradiation)
- anions (competitively inhibit the Na/I pump)
- Surgical resection (thryoidectomy)
Thioamides used in the U.S.
PTU (propylthiouracil)
methimazole
Mechanism of action of thioamides
Inhibition of thyroid peroxidase which inhibits:
- the ionization (of iodide)
- organification (attachment to thyroglobulin)
- coupling (formation of T3 and T4)
Major side effect of thioamides
Agranulocytosis
hepatitis
lupus-like syndrome
Which thioamide is used most commonly? why?
Methimazole
More effective. Less side effects (PTU known to cause hepatic toxicity especially in children)
Contraindicated in pregnancies because it has more teratogenic effects on fetus
Which thioamide is used in pregnancy? Why?
PTU
- does not cross (or crosses less) the placenta than methimazole
- methimazole has teratogenic effects
How are thioamides adminstered?
If the patient has thyrotoxicosis, how can the drugs be given?
Normally given orally.
If thyrotoxicosis (excessive hormone in circulation that can be causing some major symptoms), need to bypass the first-pass metabolism
- IV
- rectally (blood vessels in rectum can directly dump into systemics and bypass the liver)