thyroid Flashcards
hypothyroid drugs
levothyroxine (T4)/ synthroid
thryid USP (T4, T3)/ armour thyroid
liothyronine (T3)/ cytomel
levothyroxine (T4)/ synthroid
thryoid hormone replacement- SYNTHERIC- dosed in MCG
for hypothyroidism, TSH suppression in select nodule or thyroid CA
MOA- replaces normal levels of T4 & T3
PO- 70% absorption, slow onset of action(1 wk 1/2 life). track serum TSH- PARQ on cardiac sxs(angina, palpitations, tachycardia, heat intolerance)
SE- toxicity related to thyroxine lvls- palpitations, tachycardia, heat intolerance, anxiety
**long term elevation of T4 may accelerate cardiac dz & osteoporosis
**ADDISON’S PTS- tx cortisol lvls before tx’ing thyroid(do not give tyroid meds)- will cause circulatory collapse w/o stable cortisol
thyroid USP/ armour
thyroid hormone- dessicated animal thyroid gland- dosed in MG or GRAINS
for hypothyroisim
MOA- replaces both T4 & T3
PO- standardized to iodine content- 0.2% iodine- 38mcg T4 & 9 mcg T3 for each 60mg dose(1 grain)
SE- similar to synthetic- follow clincial serum lvls of TSH- begin at low dose for pts >65yo, or CAD
equivalent doses of Thyroid USP & Synthroid
60mg Thyroid USP = 100mcg of Synthroid
Liothyronine/ Cytomel
thyroid hormone replacement- synthetic T3- dosed in MCG
for pts w/hypothyroidism whom are intolerant to T4, myxedema coma, wilson’s syndrome
MOA- replaces T3
PO/IV- 100% oral absoprtion, rapid onset, 1/2 life several hrs
SE- similar to T4, higher peaks & troughs of T3 inc CAD & osteoporosis
equivalent doses of thyroid
60mg thyroid USP/ armour =
100mcg T4/ synthroid =
25mcg of T3/ cytomel
T4:T3 ratio
T4:T3 = 4:1
hyperthyroid drugs
methimazole/ tapazole propylthiouracil (PTU) propanolol/ inderal iodine/ iodide radioactive iodine (131I)
methimazole/ tapazole
thionamide
for hyperthyroidism- grave’s dz- can control thryoid until definitive therapy is used- may achieve euthyroid on its own
MOA- inhibits transformation of inorganic iodine to organic iodine- blocks produciton of thryoxine. ibhibits coupling of iodotyrosine to form T3 from T4- minimal effect of blocking peripheral conversion
PO- not used for thyroid storm
SE- hypothyroism, rash, edema, arthralgias, AGRANULOCYTOSIS is worst. usu not given beond 6-12 mos period- can cross the placental
propylthiouracil (PTU)
thionamide
for hyperthyroidism(grave’s dz)- may help achieve euthyroid, but usu just to control thyroid until definitive therapy completed
MOA- inhibits transformation of inorgain iodine to organic iodine- blocks T4-T3 & coupling of iodotyrosine- ** noteable effect of blocking the peripheral conversion of T4 to T3- affects production of thyroid but NOT the stored hormone
PO- usu used AFTER thyroid storm is stabilized until definitive tx is reached
SE- hypothyroidism, rash, edema, arthralgias, AGRANULOCYTOSIS, CATEGORY D- safer than methimazole during pregnancy
propanolol/ inderal
non-selective beta blocker
for blockade of adrenergic sxs of hyperthyroidism(tachycardia, anxiety)- **emergent tx of thyroid storm
MOA- beta 1 & beta 2 receptor blockade
PO/IV
SE- fatigue, sedation, impotency, depression
iodine/ SSKI
elemental iodine
for hyperthyroidism, thyroid storm
MOA- large doses of iodine inhibit the release of thyroxine from the thyroid gland
PO/IV- usu givenin the form of SuperSaturated Potassium Iodide(SSKI)
SE- rash, fever, beneficial for 2-3wks untl the thyroid will adapt
radioactive iodine (131I) therapy
- abalation therapy- definitive therapy for hyperthyroidism & selective CA
- genreally minimal systemic effects since the thyroid absorbs nearly all the iodine absorbed by the body
- actual radioactivity is gone within 3-5 days, but cell destruction continues for several wks
- may cause tenderness & swelling intially, N/V
- no evidence of inc malignancy risk for thyroid or other head/neck structures
- prior tx to create euthryroid by anti-thyroid drugs
- CATEGORY X
- acute leukemia has been reported- bone marrow depression
- requires lifelong thyroid replacement following tx
radioactive iodine (131I)
radioactive isotope
for thyroid gland ablation- graves, nodules, some thyroid CA
MOA- radioactive emmision of beta particles results in destruction of thyroid tissue
PO- takes wks for destruciton to be complete
SE- results in hypothyroid- sprem banking may be required for males going under tx, may have dec counts for up to 2 yrs
-CATEGORY X- preganancy should be delayed 6-12 mos after therapy
thyroid storm
may occur in hyperthyroid pts who become septic- hyperthyroid pts undergoing surgery are at risk of developing a “storm” if thyroid fxn has not be blunted previously
-high fever, irritability, delirium, vomiting, diarrhea, dehydration, hypotension, vascular collapse
-coma & death may occur
TX- beta blockade, IV iodine- stuns thyroid’s ability to utilize iodine to synthesize hormone
