Thyroid Drugs

Question 1

Levothyroxine sodium

Answer 1

• Trades: Eltroxin, Synthroid
• Used for hypothyroidism
• It’s a synthetic version of T4
• Given to replace what the thyroid gland cannot produce to achieve normal thyroid levels
• Levels should be initially monitored every 4-6 weeks until TSH normalized
• Common doses range from 25mcg-300mcg
• Taken on empty stomach 30 min before food, or at night 4 hours after last meal
• Avoid taking iron supplements within 4 hours of this medication
• Iron salts may decrease serum concentration of levothyroxine, decreases its efficacy

Question 2

desiccated thyroid

Answer 2

• Used for hypothyroidism
• Generic: desiccated thyroid (Thyroid)
• Not commonly used
• Desiccated animal thyroid gland
• Common doses 30-120mg
• Monitoring similar to levothyroxine

Question 3

tapazole (thiamazole)

Answer 3

• common doses from 15-60mg/day in adults (rarely used)
• Both are thioamide antithyroid drugs
• Both inhibit the synthesis of thyroid hormones (inhibit the incorporation of iodine molecules which is needed to make T3 and T4)
• Overall effect: decrease in thyroid hormone levels
• Both can be harmful in pregnancies
• Monitor T4, T3 after initiation and repeat if dose is adjusted (~4-6 weeks)
• TSH, CBC, liver function tests (initially and as required)

Question 4

Propylthiouracil

Answer 4

• common doses range from 300-900mg in adults
• Approximately 2 weeks of therapy with propylthiouracil may be necessary before symptoms improve.
• Both are thioamide antithyroid drugs
• Both inhibit the synthesis of thyroid hormones (inhibit the incorporation of iodine molecules which is needed to make T3 and T4)
• Overall effect: decrease in thyroid hormone levels
• Both can be harmful in pregnancies
• Monitor T4, T3 after initiation and repeat if dose is adjusted (~4-6 weeks)
• TSH, CBC, liver function tests (initially and as required)