Thyroid And Antithyroid Drugs

Question 1

What are the drugs for hyperthyroidism?

Answer 1

Antithyroid drugs: thioamides, potassium iodide
Radioactive iodine
Adjunctive drugs: beta blockers, calcium channels blockers, corticosteroids

Question 2

What are the drugs for hypothyroidism?

Answer 2

Levothyroxine, liothyronine

Question 3

What are the causes of hyperthyroidism?

Answer 3

Grave’s disease- most common
Too much iodine
Over medication with synthetic thyroid hormone

Question 4

What are the manifestations of hyperthyroidism?

Answer 4

Hot, heat intolerance
Moist skin, thin air 
Retraction of eye lids with wide stare
Exophthalmos
Tachycardia, heart failure, arrhythmia 
Nervousness

Question 5

What are the thioamides drugs?

Answer 5

Methimazole

Propylthiouracil (PTU)

Question 6

What are the MOA of the thioamides?

Answer 6

Prevent thyroid hormone synthesis by inhibiting iodination and coupling reactions
PTU also inhibits conversion of T4 to T3
Slow onset: takes 3-4 weeks to deplete stored T4

Question 7

What are the pharmacokinetics and pharmacodynamics of the thioamides?

Answer 7

Methimazole- 10 times more potent and longer half life(6h) than PTU(1.5hr)
Methimazole: oral once a day
PTU: oral every 8 hrs

Question 8

What are the clinical use of the methimazole?

Answer 8

Drug treatment f choice for treatment of hyperthyroidism

Question 9

What is the clinical use of PTU?

Answer 9

Preferred during the 1st trimester of pregnancy
Drug of choice for thyroid storm due to inhibition of conversion of T4 to T3
For those having adverse reactions to methimazole

Question 10

What are the adverse effects of The Thioamides?

Answer 10

Hepatic toxicity (PTU>>)
Hepatic failure
Liver function closely monitored especially with PTU

Question 11

What is the MOA of potassium iodide?

Answer 11

Inhibit thyroid hormone release and synthesis

Transient effect due to escapability of gland

Question 12

What is the clinical use of the potassium iodide?

Answer 12

Decreases the size and vascularity of thyroid gland before surgery (7-10 days tx)
Inhibits uptake of radioactive iodine: protects gland from damage

Question 13

What are the adverse effects of the potassium iodide?

Answer 13

Unpleasant taste, gastritis
Salivary gland inflammation
Conjunctivitis

Question 14

What is the MOA of RAI?

Answer 14

Causes destruction of parenchymal cells in the thyroid

Question 15

What is the clinical use of RAI?

Answer 15

Definitive therapy for hyperthyroidism
Has a permanent effect
May be used after patients are treated with thioamides to become euthyroid

Question 16

What are the precautions and contraindications of RAI?

Answer 16

Patients must be capable of following radiation safety procedures
Do not use in pregnant or nursing women

Question 17

What are the adverse effects of RAI?

Answer 17

Permanent hypothyroidism in most patients(90%)

Monitor thyroid function and initiate levothyroxine if necessary

Question 18

What are the clinical uses of the adjunct therapies?

Answer 18

Propanolol- reduces conversion of T4 to T3
CCB (Diltiazem, Verapamil)- patients with beta blockers contraindications (asthma patients)
Corticosteroids- reduce conversion of T4 to T3, inhibits TSH secretion

Question 19

What are the major causes of hypothyroidism?

Answer 19

Hashimoto’s disease
Surgical removal
Radiation treatment

Question 20

What are the manifestations of hypothyroidism?

Answer 20

Cold intolerance 
Pale, dry skin
Lethargy fatigue
Weight gain
Decrease metabolic rate

Question 21

What is the clinical use of levothyroxine?

Answer 21

Hypothyroidism
Cretinism- to prevent irreversible mental retardation in newborns
Myxedema coma
TSH suppression therapy

Question 22

What are the adverse effects of levothyroxine?

Answer 22

May produce symptoms of hyperthyroidism