Thyroid Drugs

Question 1

levothyroxine

Answer 1

Thyroid hormone
T4
MOA: activation of T3 receptors
Use: hypothyroidism, coronary artery disease
Treatment of choice: more stable, low cost, easy lab measurement, 7 day half life
Adverse effects:
-child: restlessness, insomnia, accelerated bone maturation
-adult: nervousness, heat intolerance, palpitations, tachycardia, weight loss
-geriatric: atrial fibrillation, osteoporosis

Question 2

liothyronine

Answer 2

Thyroid hormone
T3
MOA: activation of T3 receptors
Use: hypothyroidism, coronary artery disease
1 day half life
Adverse effects:
-child: restlessness, insomnia, accelerated bone maturation
-adult: nervousness, heat intolerance, palpitations, tachycardia, weight loss
-geriatric: atrial fibrillation, osteoporosis

Question 3

liotrix

Answer 3

Thyroid hormone
T3+T4
MOA: activation of T3 receptors
Use: hypothyroidism, coronary artery disease
Adverse effects:
-child: restlessness, insomnia, accelerated bone maturation
-adult: nervousness, heat intolerance, palpitations, tachycardia, weight loss
-geriatric: atrial fibrillation, osteoporosis

Question 4

methimazole

Answer 4

Anthithyroid-thioamides
MOA: inhibit peroxidase reaction, iodine organification, and coupling of iodotyrosines
Use: hyperthyroidism
Adverse effects: rash, nausea, GI distress, agranulocytosis, altered taste and smell
Cross placental barrier–>fetal hypothyroidism

Question 5

propylthiouracil

Answer 5

Anthithyroid-thioamides
MOA: inhibit peroxidase reaction, iodine organification, and coupling of iodotyrosines
Use: hyperthyroidism, fast acting–>thyroid storm
Adverse effects: rash, nausea, GI distress, agranulocytosis, severe hepatitis
Bound to plasma protein–>less cross placental barrier

Question 6

Potassium iodide

Lugol’s solution

Answer 6

Antithyroid agents-Iodides
MOA: inhibit proteolysis of thyroglobulin–> inhibit hormone release; inhibit organification; decrease vascularity, size, and fagility of hyperplastic gland
Uses: hyperthyroidism, thyroid storm
Adverse effects: metallic taste, sore gums, teeth, headache, sneezing, cough, skin lesions, hypersenstivity, angioedema, laryngeal edema, fetal goiter
Only inhibit 2-8 wks b/c decrease in Na/I transporter expression
Delays onset of thioamide therapy due to accumulation of iodide

Question 7

radioactive iodine

Answer 7

Antithyroid agent
123I and 131I
MOA: beta rays destroy parenchymal cells of thyroid, gamma rays used to detect conc. of RAI remaining in glands
Use: hyperthyroidism–dose so not all cells destroyed
Adverse effects: hypothyroidism, leukemia, neoplasia
Contraindicated in pregnancy

Question 8

perchlorate
pertechnetate
thiocyanate

Answer 8

Antithyroid-anion inhibitor
MOA: inhibit energy dependent uptake of iodide into thyroid cell that is mediated by Na/I symporter
Use: iodide-induced hyperthyroidism (amiodarone causing)
Adverse effects: perchlorate can cause aplastic anemia
Can be overcome by large dose of iodide

Question 9

propranolol

Answer 9

Key adjunts
MOA: antagonize Beta 1 and Beta 2 adrenergic receptors; inhibit conversion of T4 to T3
Use: hyperthyroidism; control tachycardia, hypertension, and atrial fibrillation; useful for thyroid storm
Adverse effects: asthma, AV block, hypotension, bradycardia

Question 10

diltiazem

Answer 10

Key adjunct
MOA: control tachycardia in asthmatic
Use: hyperthyroidism

Question 11

barbiturates

Answer 11

Key adjunct
MOA: increase T4 metabolism
Use: hyperthyroidism

Question 12

bile acid sequestrants

Answer 12

Key adjunct
MOA: increase biliary T4 excretion
Use: hyperthyroidism