Antithyroid Drugs

Question 1

Antithyroid Drugs types?

Answer 1

1. Thioamide
2. Lugol’s Iodine
3. 131- I
4. Synthetic Thyroxine

Question 2

Thioamide drugs?

Answer 2

• PTU does not cross placenta (can use in
pregnancy)

• Carbimazole

Question 3

Thioamide mechanism of action?

Answer 3

• Inhibits thyroperoxidase: oxidation of iodine, coupling, and release of T3/T4
• PTU inhibits peripheral T3 conversion

Question 4

Thioamide Side Effects & Contraindications?

Answer 4

• Arthralgia
• Blood dyscrasiasis
• Cholestatic jaundice
• Drug (maculopapular, pruritic) rash
• Enlarged lymph nodes
• Fever
• Dizziness & Headache

Question 5

Lugol’s Iodine drugs?

Answer 5

• Iodine in KI

Question 6

Lugol’s Iodine mechanism of action?

Answer 6

• Inhibits iodine uptake, coupling and release of T3/T4

* Can be source of iodine in endemic goiter

Question 7

Lugol’s Iodine Side Effects & Contraindications?

Answer 7

• ‘iodism’ with oral ulcers and throat pain with brassy taste
• Allergy leading to glottis swelling

Question 8

131- I drugs?

Answer 8

• Alternative to surgery

Question 9

131- I mechanism of action?

Answer 9

• Releases gamma and beta (damaging) particles killing surrounding follicular cells within 2mm margin (sparing stroma)
• Slow acting and requires interim therapy

Question 10

131- I Side Effects & Contraindications?

Answer 10

• Interim therapy with PTU and beta blocker
• Delayed hypothyroidism as tissue is damaged
• Easy to administer (oral)

Question 11

Synthetic Thyroxine drugs?

Answer 11

• Synthetic L-thyroxine (T3)

* Synthetic L-ionothyronine (T4)

Question 12

Synthetic Thyroxine mechanism of action?

Answer 12

• Replace T3 / T4
• T4 needs higher dose as it is less active
• Larger dose in children, higher metabolic rate

Question 13

Synthetic Thyroxine Side Effects & Contraindications?

Answer 13

• Hyperthyroidism

* Underlying cardiac disease exacerbated