Unit 5-Thyroid Flashcards
Levothyroxine sodium
Drug class
Synthetic thyroid hormone (T4)
Levothyroxine sodium
Mechanism
Converted to T3 in liver; T3 binds toTR complex to influence gene expression
Levothyroxine sodium
Uses
Drug of choice for hypothyroidism (longer half-life than T3)
Levothyroxine sodium
Side effects
Hyperthyroidism: heart palpitations, nervousness, shaking, heat intolerance, weight loss
“Start low, go slow” in patients with angina pectoris, CAD, and elderly; requires periodic monitoring and adjustment (especially during pregnancy); not effective in Chronic Fatigue Syndrome
Liothyronine sodium
Drug class
Synthetic thyroid hormone (T3)
Liothyronine sodium
Mechanism
T3 binds to TR complex in nucleus to influence gene expression
Liothyronine sodium
Uses
Acute management of hypothyroidism (rapid effect);
myxedema coma (IV formulation)
4X as potent as T4, but not desirable for chronic replacement (less stable, more costly, transient high levels)
Liothyronine sodium
Side effects
Hyperthyroidism: heart palpitations, nervousness, shaking, heat intolerance, weight loss
Liotrix
Drug class
Synthetic thyroid hormone (T4 & T3)
Liotrix
Mechanism
Converted to T3 in liver; T3 binds toTR complex to influence gene expression
Liotrix
Uses
Thyroid hormone replacement therapy (4:1 mix of T4:T3; not used much)
Liotrix
Side effects
Hyperthyroidism: heart palpitations, nervousness, shaking, heat intolerance, weight loss
Propylthiouracil
Drug class
Thioamide (thyroid peroxidase inhibitors)
Propylthiouracil
Mechanism
Inhibit organification of iodide and coupling of iodotyrosine; also reduces peripheral deiodination of T4 to T3
Propylthiouracil
Uses
Hyperthyroidism; thyrotoxicosis (high dose); drug of choice for hyperthyroidism during pregnancy
Propylthiouracil
Side effects
Rare side effects: hepatitis, agranulocytosis (higher than methimazole), lupus-like syndrome
Discontinue and use radio-iodine if patient develops agranulocytosis or drug-induced lupus
Methimazole
Drug class
Thioamide (thyroid peroxidase inhibitors)
Methimazole
Mechanism
Inhibit organification of iodide and coupling of iodotyrosine; active metabolite of carbimazole; less effect on T4 to T3 conversion
Methimazole
Uses
Hyperthyroidism; thyrotoxicosis (high dose)
Methimazole
Side effects
Rare side effects: hepatitis, agranulocytosis (less than propylthiouracil), lupus-like syndrome
Discontinue and use radio-iodine if patient develops agranulocytosis or drug-induced lupus
Methimazole is a possible teratogen
Carbimazole
Drug class
Thioamide (thyroid peroxidase inhibitors)
Carbimazole
Mechanism
Prodrug converted to methimazole; Inhibits organification of iodide and coupling of iodotyrosine; less effect on T4 to T3 conversion
Carbimazole
Uses
Hyperthyroidism; thyrotoxicosis (high dose)
Carbimazole
Side effects
Rare side effects: hepatitis, agranulocytosis, lupus-like syndrome
Discontinue and use radio-iodine if patient develops agranulocytosis or drug-induced lupus; not available in US
