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Pharm 7 > Thyroid > Flashcards

Thyroid Flashcards

0
Q

T3 drug form, active metabolite, limited specialized uses

A

Liothyronine

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1
Q

T4 drug form, most replacement uses

A

Levothyroxine

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2
Q

Thiamine, peroxidase inhibitor, effective once daily

A

Methimazole

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3
Q

Thioamide, peroxidase inhibitor, many specific uses

A

Propylthiouricil

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4
Q

Prior to thyroidectomy, for thyroid storm, for radiation emergencies

A

Iodides

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6
Q

Alternative to surgery for destruction of thyroid

A

Radioactive iodide

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7
Q

T3 or T4: What is 5x more potent?

A

T3

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8
Q

T3 or T4: What is more rapidly metabolized?

A

T3. T4 is more protein bound so slows degradation

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9
Q

Levothyroxine has (SLOW/FAST) onset and (SHORT/LONG) duration?

A

Slow, Long. Converted to more active T3 in body.

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10
Q

T/F: Levothyroxine (T4) given IV is preferred even in myxedema coma, due to its more predictable effects on patients?

A

True

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11
Q

T/F: Switching brands of levothyroxine should be avoided.

A

True- due to differences

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12
Q

What is rarely used in chronic therapy of hypothyroidism due to rapid onset, too-marked effects, and too-short half life?

A

Liothyronine

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13
Q

When is liothyronine indicated?

A
  • Has specific and limited indications.
  • In thyroid cancer, for maintaining supressive effects while patients are tapered off of T4 prior to surgery and for the more rapid onset while T4 takes effect after surgery.
  • For similar short term support prior to and following radioiodine.
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14
Q

Levothyroxine and liothyronine can be given ______.

A

Orally

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15
Q

Side effects of levothyroxine and liothyronine?

A

Minor- generally overdose leading to hyperthyroidism

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16
Q

What can alter thyroid function and/or TH absorption?

A

Numerous drugs along with effecting protein binding and metabolism.
-Physiological status and/or other diseases also can change TH effectiveness and may require dosage adjustments.

17
Q

Symptomatic relief for hyperthyroidism includes…

A

Propranolo or diltiazem to treat symptoms primarily due to sympathetic nervous system stimulation

18
Q

Disease modifying treatments of hyperthyroidism

A

Anti-thyroid drugs: Thioamides, iodides

Thyroid gland ablation: Therapeutic radioiodine, partial thyroidectomy

19
Q

List 2 thioamides and their MOA

A

Propylthiouracil and Methimazole.

  • Inhibit peroxidase enzyme, both iodination and coupling steps.
  • Do not block release of preformed THs, therefore exhibit a latent period of weeks before colloid is depleted of stored TH.
  • May have direct anti-autoimmune effects as well
20
Q

What also inhibits peripheral conversion of T4 to T3, therefore more rapid effect, so it is preferred in treating thyroid storm?

A

Propylthiouracil

21
Q

Therapeutic use of Thioamides (Propylthiouracil and Methimazole)

A

Non-destructive

  • Useful for immediate control of thyroid hormone production.
  • Average therapy about 1 year, but disease remission in only 30% of pts.
  • Radioiodine or surgery required if relapse occurs after thioamides.
22
Q

How are thioamides (Propylthiouracil and Methimazole) taken? Concentrated? Metabolized?

A

Orally,
Cleared from circulation and concentrated in thyroid.
Metabolism by conjugation and excretion in urine.

23
Q

Propylthiouracil or Methimazole? Which is more potent?

A

Methimazole

24
Q

Propylthiouracil or Methimazole? Short half life and must be given 2-4 times/day

A

Propylthiouracil

25
Q

T/F: The 10x higher potency of methimazole is a significant advantage?

A

False: is not

-Longer duration is important because helps with compliance

26
Q

Adverse effects of both Propylthiouracil and Methimazole?

A
  • Agranulocytosis: rare, can be fatal, usually in 1st few months, symptoms of sore throat and fever, immediately discontinue use, dont use thioamide in patient again.
  • Skin rash, drug fever, arthralgia, myalgia, others.
  • Hypothyroidism if dose too high
27
Q

Propylthiouracil or Methimazole? Which causes liver toxicity/failure?

A

Propylthiouracil- a reason why Methimazole is preferred drug along with the longer duration of action.

28
Q

When is Propylthiouracil indicated?

A
  • Pregnancy and breast feeding.

- Thyroid storm

29
Q

Potassium iodide, sodium iodide, and molecular iodide are given orally as solutions or tablets in hyperthyroidism and are examples of what?

A

Iodides

30
Q

Pharmacologic effects of Iodides

A
  • Acute inhibition of synthesis and release of THs; no effect on T4–>T3 conversion.
  • Decrease size and vascularity of thyroid gland.
31
Q

Therapeutic uses of iodides

A
  • During thyroid storm, to inhibit synthesis and release of THs; effect is rapid but of short duration, so iodides not useful for long term treatment.
  • During last 10 days before thyroidectomy, to make cleaner safer surgery.
  • Used in radiation emergencies, eg: nuclear power plant accidents, to intentionally compete with released radioactive iodine.
32
Q

T/F: Iodides should be used prior to radioiodine therapy?

A

False- should not be used because they would compete for uptake.

33
Q

Side effects of iodides:

A

Mild: sore throat, burning mouth, rash, diarrhea

34
Q

What are present in foods such as cabbage and turnips and act s natural “goitrogens”?

A

Iodides

35
Q

Radioactive Iodine:

1) Isotope used?
2) Half life= ____days
3) 85% weak ____ radiation (travels 1-2 mm in tissue); useful for localized tissue destruction.
4) 15% stronger _______ radiation; useful for diagnosis.

A

A) 131 I
B) 8
C) Beta
d) Gamma

36
Q

1) Small doses of radioiodine are used for what?

2) Large doses of radioiodine are used for what?

A

1) Tracer studies of uptake for diagnosis of hyperthyroidism, assessment of anatomy and function of thyroid tissue, and localization of metastatic thyroid cancer.
2) Destruction of thyroid tissue. Given orally as solution or capsules; concentrated in gland.

37
Q

Radioiodine is contraindicated in…

A

Pregnancy, nursing and young children

38
Q

High doses of radioiodine can cause what?

A

Radiation thyroiditis and salivary adenitis

39
Q

Treatment of choice for hyperthyroidsim in:
A) Young
B) Older
C) Pregnant

A

A- Methimazole
B- Radioactive iodine
C- Propylthiouracil

Pharm 7 (10 decks)

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