notes Flashcards
drugs that can cause hypothyroidism
amiodarone carbamazepine eslicarbazepine oxcarbazepine interferons lithium phenytoin TKIs especially sunitinib
What is the most common cause of hypothyroidism?
Hashimoto’s disease - an autoimmune disease
If left untreated, what life threatening emergency can occur it hypothyroidism?
myxedema coma
diagnosis of hypothyroidism?
low free T2
high TSH
monitoring parameter in hypothyroidism
TSH q4-6 weeks until levels are normal then q4-6 months rarely use T4
Too high doses of thyroid replacement hormone can lead to what in elderly pts?
atrial fibrillation and fractures
how to treat hypothyroidism in pregnancy
levothyroxine is safe in pregnancy and aggressive treatment is warranted (30-50% increase in dose)
What is the drug of choice in hypothyroidism?
levothyroxine (T4) - use same formulation
What are other supplemental medications used in hypothyroidism?
liothyronine (T3, Cytomel, Triostat) dessicated thyroid (T3 & T4, Armour Thyroid)
How should levothyroxine be taken?
60 minutes before breakfast or 3 hours after dinner at bedtime. Should be taken consistently.
What is the dose of levothyroxine in pts w/ CAD?
12.5 to 25 mcg/day
warnings levothyroxine
decrease dose in CAD and decreased BMD
levothyroxine brand
Synthroid, Levoxyl, Tirosint, Unithroid
SE levothyroxine
if euthyroid, no symptoms. Hyperthyroid symptoms if too high of dose
drugs that decrease levothyroxine absorption
space out by 4 hours: aluminum antacids calcium iron magnesium cholestyramine sucralfate sevelamer vitamins containing ADEK, iron, folate orlistat
space out by 3 hours:
Kayexelate
space out by 2 hours:
lanthanum
drugs that decrease thyroid hormone levels
estrogen
SSRIs
hepatic inducers
drugs that decrease conversion of T4 to T3
amiodarone
propylthiouracil
steroids
thyroid hormones are highly protein bound. drugs that can cause protein binding displacement
NSAID
salicylates >2g/day
phenytoin
heparin
levothyroxine and warfarin
can increase PT/INR
levothyroxine and digoxin
decrease digoxin levels
levothyroxine and theophylline
decrease theophylline levels
levothyroxine and antidiabetic agents
decrease antidiabetic agent levels
levothyroxine tablet colors
Orangutans Will Vomit On You Right Before They Become Large, Proud Giants
what is IV:PO levothyroxine ratio
0.75:1
Liotrix brand
whats in it?
Thyrolar
contains levothyroxine and liothyronine in a 1:4 ratio
What is the most common cause of hyperthyroidism?
Grave’s disease
which drugs can cause hyperthyroidism?
iodine
amiodarone
interferon
(amiodarone and interferon can also cause hypothyroidism)
What agent is typically used first for symptom control in hyperthyroidism?
beta blockers to control palpitations, tachycardia, tremors
initially when treating hyperthyroidism with drugs, how long does it take for symptom control?
1-3 months on a high dose and then dose reduce to prevent hypothyroidism
What are thionamides?
they are used in hyperthyroidism to prevent oxidation of iodine. propylthiouracil also prevents conversion of T4 to T3 in the periphery.
pregnancy and thionamides
1st trimester: PTU
2 and 3 trimester: switch to methimazole
brand methimazole
Tapazole
BW PTU
acute hepatic failure, severe liver injury
SE methimazole, PTU
GI upset (take w/ food to decrease) hepatitis, agranulocytosis
which thionamide is preferred in thyroid storm?
PTU
Iodides used in hyperthyroidism
Lugol’s solution - potassium iodide and iodine
SSKI, Thyroshield - saturated solution potassium iodide
why is potassium iodide recommended right after thyroid radiation?
It blocks the accumulation of radioactive iodine therefore preventing thyroid cancer
Drug treatment in Thyroid storm
PTU 500-1000mg LD followed by 250mg q4h inorganic iodide w/ Lugol's or SSKI beta blocker systemic steroids aggressive cooling with acetaminophen and cooling blankets supportive therapy
what is the starting dose of levothyroxine?
- 6 mcg/kg/day
12. 5 to 25 in CAD
PTU and warfarin
can decrease INR
