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Flashcards in Kinder, thyroid drugs Deck (57):
1

What thyroid agents do we use

levothyroxine T4
liothyronine T3

2

what are the antithyroid agents

methimazole
propylthiouracil
potassium iodide

3

how is iodide transferred into thyroid gland

Na/iodide symporter

4

what anions impair iodide transport

thiocyanate, pertechnetate, perchlorate

5

how does iodide travel to the follicular lumen

iodide transporter called pendrin

6

what oxidizes iodide

thyroidal peroxidase

7

what do thioamide drugs block

thyroid peroxidase

8

what drugs can inhibit 5' deiodinase needed to convert T4 to T3

amiodarone, iodinated contrast media, beta blockers, corticosteroids, severe illness, starvation

9

what inhibits TSH release

somatostatin, dopamine T3T4

10

thyroid effects are from what process

activation of nuclear R leading to protein synthesis

11

which type of thyroid syndrome causes decreased drug metabolism? increased warfarin requirement?

hypothyroidism

12

where is T4 absorbed

duodenum and ileum

13

what can alter absorption of given thyroid hormones

severe myxedema with ileus

14

how does T3 T4 clearance change in hypo and hyper thyroidism

in hyper clearance is increased
in hypo clearance is decreased

15

what agents increase hepatic CYP and enhance degradation of thyroid hormone

rifampin, phenobarbital, carbamazepine, phenytoin, HIV protease inhibitors

16

what agents interfere with T4 absorption

oral bisphosphonates, bile acid sequestrants, cipro, ppis, sucralfate, antacids, bran, soy, coffee

17

what agents induce autoimmune thyroid disease with hypo or hyperthyroidism

INF-a
lithium
amiodarone

18

CI T2 liothyronine

those with cardiac disease because increased risk for cardiotoxicity

19

why is T3 replacement not commonly used

requires multiple daily dosing, higher cost, difficulty monitoring

20

what are the thioamides

meth`imazole, propylthiouracil

21

MOA thioamides

prevent thyroid hormone synthesis
inhibit thyroid perozidase catalyzed reactions, blocks iodine organification, blocks coupling of iodotyrosines

22

what additional affect does PTU have

peripheral deiodination T4 to T3

23

onset of action of thioamides and why

slow 3-4 weeks before stores of T4 depleted because affects synthesis not release

24

What thioamide is more portent

methimazole

25

what thioamide is rec for pregnant women in 1st trimester or someone in thyroid storm

PTU

26

why is PTU preferred in pregnancy

protein bound so crosses placenta less readily

27

adverse effects to thioamides

maculopapular rash with fever sometimes
urticarial rash, vasculitis, lupus-like reaction, lymphadenopathy, hypoprothrombinemia, exfoliative dermatitis, acute arthralgia

28

What is an adverse effect PTU

severe hepatitis

29

most dangerous complication with thioamides

agranulocytosis

30

What are the anion inhibitors we use in hyperthyroidism

perchlorate, pertechnetate and thiocynate which competitively inhibit iodide transport mech blocking iodide uptake

31

what is MOA potassium iodide

inhibit iodide rganification and hormone release, decrease size and vascularity of hyperplastic gland

32

major action potassium iodidie

inhibits hormone release (possibly inhibition thyroglobulin proteolysis)

33

therapeutic use of potassium iodide

thyroid storm
preoperative reduction hyperplastic gland
block thyroidal uptake of radioactive isotopes of iodine in a radiation EM
after thioamide therapy

34

why do you use potassium iodide after thioamide use

may delay thioamide by increasing intraglandular stores of iodine

35

whye should iodides never be used alone

gland escapes block in 2-8 weeks and withdrawl may produce severe exacerbation of thyrotoxicosis in iodine enriched gland

36

Adverse effects iodidies

uncommon
acneiform rash, swollen salivary glands, mucous membrane ulcerations, conjunctivitis, rhinorrhea, drug fever, metallic taste, bleeding disorders, anaphylactic reactions

37

are iodides used in pregnancy

no because cross placenta and can cause fetal goiter

38

MOA radioactive iodine

destruction of thyroid parenchyma thorugh epithelial swelling, necrosis, follicular disruption, edema and leukocyte infiltration

39

advantages radioactive iodine

easy administration, effective, low expense, absence pain

40

CI RI iodine

pregnancy or breast feeding
destroys fetal thyroid gland

41

which medications can improve the Sx of hyperthyroism but do not alter the thyroid hormone

beta blockers: metoprolol, propanolol, atenolol

42

general Tx strategy for hashimoto

levothyroxine unless drug induced hypothyroidism

43

how long does it take for levothyroxine to work

6-8 weeks

44

signs of thyroxine toxicity

children: restless ness, insomnia, acclerated bone maturation and growth
adults: increased nervousness, heat intolerance, episodes of palpitations and tachy, unexplained weight loss

45

chronic overTx with T4 can lead to what

a fib and accelerated osteoporosis

46

hypothyroid patient has progressive weakness, stupor, hypothermia, hypoventilation, hypoglycemia, hypoNa and water intoxication, shocky

myxedema coma! medical EM!!

47

Tx myxedema coma

IV levothyroxine loading dose with following mainta=enance doses

48

What is your worry in myxedma with patient who has CAD

low levels thyroxine protect heart from increasing demands so want to avoid provoking cardiac event with drugs

49

what is preferred patient for antithyroid drugs

young patients with small glands and mild disease

50

preferred patient for thyroidectomy

large glands or multinodular goiters hyperthyroidism

51

what should you do prior to thyroidectomy

Tx with potassium iodide 10-14 days prior to diminish gland vascularity

52

preferred patient for radioactive iodine

over 21 y.o
no heart disease

53

how do you Tx patient with heart disease with Radioactive iodine

antithyroid drugs until euthyroid
stop medication 3-5 days before RAI, may resume 3-7 days post
taper antithyroid medication over 4-6 weeks as thyroid functio normalizes

54

what are adjunts to antithyroid therapy

beta blockers to control tachy, HTN and a fib

55

if patient cannot have beta blocker how do you treat heart when alost on antithyroid meds

diltiazem
CaCh blocker

56

management thyroid storm

beta blocker
potassium iodidie to prevent release of thyroid hormones
PTU to block synthesis
hydrocortisone IV to protect against shock
supportive therapy for fever, or underlying diseases

57

what is used last resort to lower circulating thyroxine in thyroid storm

oral bile acid sequestrants, plasmapheresis or peritoneal dialysis