thyroid drugs Flashcards
(37 cards)
What is the drug of choice (DOC) for hypothyroidism?
Levothyroxine (Synthroid), Liothyronine, Liotrix, Thyroid USP.
How do levothyroxine and related drugs work?
They are synthetic thyroid hormones (T4, T3, or combination).
What is a major adverse effect of levothyroxine?
Overmedication can cause thyrotoxicosis (anxiety, tachycardia, chest pain, nervousness, tremors, weight loss, heat intolerance, diaphoresis, etc.).
What are the risks of chronic overmedication with levothyroxine?
Atrial fibrillation, increased fracture risk.
Is levothyroxine safe in pregnancy?
Yes, but caution in lactation, post-MI, older adults, and diabetics.
What drugs increase the risk of dysrhythmias with levothyroxine?
Catecholamines like epinephrine, dopamine, and dobutamine.
What substances block levothyroxine absorption?
Cholestyramine, colestipol, antiulcer medications, calcium, iron, magnesium, food.
What drugs increase levothyroxine metabolism?
Many antiseizure and antidepressant medications.
What is the effect of levothyroxine on warfarin?
It may increase anticoagulant effects – monitor PT/INR.
What should be monitored with levothyroxine therapy?
Vital signs, weight, height, cardiac excitability (apical pulse, angina, palpitations, dysrhythmias).
How should levothyroxine be taken?
On an empty stomach, 30-60 minutes before the first meal.
How is levothyroxine therapy initiated?
Start with a low dose and increase over a few weeks.
What is the half-life of levothyroxine?
7 days; takes ~1 month (4 half-lives) to reach a steady state.
How long does levothyroxine take to fully work?
6-8 weeks.
Is levothyroxine therapy lifelong?
Yes, and it should not be discontinued without provider approval.
Should patients switch brands of levothyroxine?
No, they should stay with the same brand.
What lab values should improve with levothyroxine?
TSH should decrease, and T4 should be within normal limits.
What are Methimazole & Propylthiouracil (PTU) used for?
Hyperthyroidism; used before surgery or in thyroid crisis.
How do Methimazole & PTU work?
They block the synthesis of thyroid hormones but do not destroy existing hormones.
How long do Methimazole & PTU take to work?
3-12 weeks for euthyroid state.
What are the uses of Methimazole & PTU?
Grave’s Disease, pre-thyroidectomy, thyroid irradiation, thyrotoxic crisis.
Which drug is preferred for hyperthyroidism?
Methimazole is the first choice.
What are the adverse effects of Methimazole & PTU?
Hypothyroidism, agranulocytosis, liver injury/hepatitis (PTU).
What are the contraindications for Methimazole & PTU?
Pregnancy/lactation (Methimazole not in 1st trimester, PTU is safe), bone marrow suppression, immunosuppression, liver failure risk.
