Thyroid & antithyroid drugs

Question 1

Levothyroxine

Answer 1

• MOA
• T₄
• activation of nuclear receptors resulting in protein synthesis
• Indications
• hypothyroidism
• Kinetics, tox, int.
• maximum effect after 6-8w

Question 2

Thioamides

Answer 2

• Antithyroid agents
• Methimazole
• Propylthiouracil (PTU)
• MOA
• inhibit thyroid peroxidase reactions
• block iodine organification
• inhibit peripheral deiodination of T₄ and T₃ (primarily PTU)
• Indications
• hyperthyroidism
• Kinetics, tox, int.
• oral, duration 24h (methimazole), 6-8h (PTU)
• delayed onset
• tox: nausea, GI-distress, rash, agranulocytosis, hepatitis (PTU black box), hypothyroidism