- Body system
- Endocrine
- Drug cards
- 2 in this guide
Drugs in this class
Other examples: Liothyronine, Propylthiouracil (PTU), Potassium iodide, Radioactive iodine.
How thyroid and antithyroid drugs work
Levothyroxine is synthetic T4. Thioamides (methimazole, propylthiouracil) block thyroid hormone synthesis; PTU also blocks conversion of T4 to T3.
Uses
- Hypothyroidism (levothyroxine)
- Hyperthyroidism and Graves disease (methimazole, PTU)
- Thyroid storm (PTU, beta blockers, iodine)
Adverse effects
- Overreplacement: tachycardia, palpitations, insomnia, heat intolerance, weight loss
- Thioamides: rash, agranulocytosis, liver injury
Nursing considerations
- Monitor TSH and free T4.
- Start levothyroxine at a low dose in older adults and in heart disease.
- With thioamides, check the CBC if fever or sore throat develop.
Patient teaching
- Take levothyroxine on an empty stomach, 30 to 60 minutes before breakfast, apart from calcium and iron.
- Report sore throat or fever while taking methimazole or PTU.
- Thyroid replacement is usually lifelong.
Thyroid and antithyroid drugs NCLEX practice questions
Answer each question to see the rationale.
3 questions. Choose an answer to see the rationale.
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When should a patient take levothyroxine?
Show answer
Answer B: On an empty stomach 30 to 60 minutes before breakfast Food, calcium and iron reduce absorption. Taking it consistently on an empty stomach gives stable levels.
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A patient taking methimazole reports fever and a sore throat. What is the priority?
Show answer
Answer C: Notify the provider and check the CBC: possible agranulocytosis Agranulocytosis is a serious adverse effect of thioamides; fever and sore throat are the warning signs.
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Which finding suggests the levothyroxine dose is too high?
Show answer
Answer A: Palpitations and insomnia Too much thyroid hormone causes signs of hyperthyroidism, such as palpitations, nervousness and insomnia.
Frequently asked questions
What are thyroid and antithyroid drugs?
Levothyroxine replaces thyroid hormone in hypothyroidism; methimazole and PTU block hormone production in hyperthyroidism. Both are adjusted using TSH and free T4.
How do thyroid and antithyroid drugs work?
Levothyroxine is synthetic T4. Thioamides (methimazole, propylthiouracil) block thyroid hormone synthesis; PTU also blocks conversion of T4 to T3.
What are examples of thyroid and antithyroid drugs?
Levothyroxine, Methimazole, Liothyronine, Propylthiouracil (PTU), Potassium iodide and Radioactive iodine.
What are the nursing considerations for thyroid and antithyroid drugs?
Monitor TSH and free T4. Start levothyroxine at a low dose in older adults and in heart disease.