Thyroid Drugs Flashcards
(14 cards)
Levothyroxine (Synthroid)
Thyroid hormone replacement. T4 only. Used for Hypothyroidism. Also TSH suppression in select cases of thyroid nodules and thyroid cancer.
MOA - Acts as thyroid hormone T4.
SFx - Palpitations, tachycardia, intolerance to heat, and anxiety. NOTE: Long term elevation of serum T4 may accelerate cardiac disease and osteoporosis!
Sxs of Hypothyroidism
Fatigue, general weakness, constipation, dry skin, hair loss, bradycardia, cold intolerance.
Thyroid hormone replacement in Addison’s Disease pts
MUST replace cortisol before thyroid. Failure to do so may result in death.
Armour Thyroid
Porcine thyroid gland. 38 mcg of T4 and 9 mcg of T3 for each 60 mg dose (1 grain). 60 mg (1 grain) of Thyroid USP produces an approximate equivalent effect of 100 mcg of Levothyroxine (synthetic T4). Used for hypothyroidism.
SFx - palpitations, tremor, same as levo. Monitor TSH levels in all pts.g
Leiothyronine (Cytomel)
Synthetic thyroid hormone, only T3. Used for pts with hypothyroidism that have intolerance to T4 replacement therapy or no improvement on T4 only. Also used for myxedema coma and “Wilson’s syndrome”.
SFx - same as other thyroid replacements. Spikes and troughs of T3 may accelerate heart disease.
Equivalent doses for thyroid replacement therapies
60 mg Armour = 100 mcg of T4 (Synthroid) = 25 mcg of T3 (Cytomel)
Which hypothyroid drugs are in dose in mg? mcg?
mg - armour (dessicated gland). mcg - synthetic T3 or T4 (cytomel, levo).
Thyroiditis factitia
Excess administration of thyroid hormone induced thyroiditis. May be inadvertent from overdose, or intentional for [and ineffective to cause] weight loss.
Methimazole (Tapazole)
Thionamide. Used for hyperthyroidism (grave’s) to control hyperthyroidism until radiation ablation tx can take place. Occasionally a hyper pt will become euthyroid after d/c. Generally not used for longer than 6-12 mo.
MOA - inhibits inorganic iodine form being converted to organic iodine and thusly blocks formation of thyroxine. DOES NOT inhibit peripheral T4 –> T3 conversion.
SFx - agranulocytosis. Monitor CBCs.
CAT D - crosses placenta. Only use in an emergent case.
Propylthiouracil (PTU)
Thionamide. Used for hyperthyroidism (grave’s). Can control hyper state until radioablation can take place. Some pts will achieve euthyroid state after d/c. Generally not used for longer than 6 - 12 mo.
MOA - blocks iodine conversion, stopping the creation of thyroxine. DOES block T4 –> T3 conversion in periphery.
SFx - agranulocytosis, monitor CBCs.
CAT D, but considered safer than methimazole in pg
Propanolol (Inderal)
Non-selective B-blocker. Used to diminish the effects of hyperthyroidism (tachycardia, anxiety). Emergent tx of thyroid storm!
MOA - B1 and B2 R blockade.
SFx - fatigue, sedation, impotence, depression.
Iodine (SSKI)
Elemental iodine. Used for thyroid storm and general hyperthyroidism.
MOA - large doses of I inhibit release of thyroxine from thyroid. Effective for 2-3 weeks, then the thyroid compensates and resumes production.
SFx - Rash, fever.
Radioactive Iodine (Isotope I-131)
Radioactive isotope used for non-surgical ablation of the thyroid gland. Prior to tx, pt must be rendered euthyroid by thionamide or SSKI
MOA - thyroid absorbs radioactive isotope and is destroyed over a period of several days. Beta particles, specifically.
SFx - NO INCREASED RISK for malignancy, bone marrow depletion in high doses. Lifelong hypothyroidism.
CAT X, obviously.
Thyroid storm
Most severe manifestation of hyperthyroidism.
SSX: high fever, irritability, delirium, vomitting, diarrhea, dehydration, hypotension and vascular collapse. Coma and death are most severe sxs.
Risk factors: surgical intervention of hyperthyroidism, sepsis in a hyperthyroid pt.
Tx: high dose iodine to stun thyroid and B-blockers.
