👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Pharmacological Therapies🔖 Free to read, print, and share
Also known as: PTU · thyroid-blocker · antithyroid drug
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Use this quick-reference guide to spot, treat, and prevent Propylthiouracil (PTU) on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Mech
Blocks thyroid hormone synthesis
Also blocks T4 → T3
📌 Use
Graves, thyroid storm
Preferred 1st trimester pregnancy
🚩 Report
Agranulocytosis → sore throat, fever
Hepatotoxicity (black box)
Bruising, bleeding
🎓 Teach
Onset weeks, take daily
Monitor CBC + LFTs
📚 Propylthiouracil (PTU) — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Propylthiouracil (PTU) is an antithyroid medication used to treat hyperthyroidism and thyroid storm by blocking the synthesis of thyroid hormone and, importantly, blocking peripheral conversion of T4 to the active T3. Because of liver toxicity risk, it is reserved for the first trimester of pregnancy and thyroid storm rather than first-line maintenance. Its life-threatening adverse effects are agranulocytosis and hepatotoxicity.
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Key points
Understand these first
Inhibits thyroid hormone synthesis and blocks peripheral conversion of T4 to T3, making it useful in thyroid storm.
Preferred antithyroid drug in the first trimester of pregnancy because methimazole has higher teratogenic risk early on.
Agranulocytosis (dangerously low white cells) is a serious adverse effect; sore throat and fever are early warning signs.
Hepatotoxicity, including liver failure, is a boxed-warning risk, more so than with methimazole.
Therapeutic effect is delayed several weeks because it blocks new hormone production, not stored hormone.
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Nursing priorities
What to do, in order
Monitor CBC for agranulocytosis and assess for sore throat, fever, or signs of infection.
Monitor liver function tests and assess for jaundice, dark urine, or right upper quadrant pain.
Assess thyroid status (heart rate, weight, temperature, energy) for response and signs of hypothyroidism from overtreatment.
Administer consistently at the same times each day to maintain stable hormone suppression.
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Red flags — report now
Escalate immediately
Sore throat, fever, or mouth ulcers — possible agranulocytosis; hold dose and report immediately.
Jaundice, dark urine, or right upper quadrant pain — possible hepatotoxicity; report now.
Never give to a nursing or first-trimester patient without confirming it is the intended antithyroid choice.
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Labs & values
Numbers to know
TSH 0.4-4.0 mIU/L
Free T4 0.8-1.8 ng/dL
WBC 5,000-10,000/mm3 (watch for agranulocytosis)
ALT/AST monitor for hepatotoxicity (ALT ~7-56 U/L)
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Patient teaching
What patients must know
Report sore throat, fever, chills, or signs of infection immediately.
Report yellowing of skin or eyes, dark urine, or upper-right belly pain.
Take the medication at the same times every day and do not stop abruptly.
Understand it may take several weeks to feel better as hormone levels fall.
Avoid foods high in iodine (kelp, seafood) unless directed.
❓ Propylthiouracil (PTU): NCLEX FAQs
What are the priority nursing interventions for Propylthiouracil (PTU)?
Monitor CBC for agranulocytosis and assess for sore throat, fever, or signs of infection. Monitor liver function tests and assess for jaundice, dark urine, or right upper quadrant pain. Assess thyroid status (heart rate, weight, temperature, energy) for response and signs of hypothyroidism from overtreatment. Administer consistently at the same times each day to maintain stable hormone suppression.
What are the warning signs of Propylthiouracil (PTU) a nurse must report?
Sore throat, fever, or mouth ulcers — possible agranulocytosis; hold dose and report immediately. Jaundice, dark urine, or right upper quadrant pain — possible hepatotoxicity; report now. Never give to a nursing or first-trimester patient without confirming it is the intended antithyroid choice.
What do I need to know about Propylthiouracil (PTU) for the NCLEX?
Inhibits thyroid hormone synthesis and blocks peripheral conversion of T4 to T3, making it useful in thyroid storm. Preferred antithyroid drug in the first trimester of pregnancy because methimazole has higher teratogenic risk early on. Agranulocytosis (dangerously low white cells) is a serious adverse effect; sore throat and fever are early warning signs. Hepatotoxicity, including liver failure, is a boxed-warning risk, more so than with methimazole.
What patient teaching is important for Propylthiouracil (PTU)?
Report sore throat, fever, chills, or signs of infection immediately. Report yellowing of skin or eyes, dark urine, or upper-right belly pain. Take the medication at the same times every day and do not stop abruptly. Understand it may take several weeks to feel better as hormone levels fall.
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Quick Tip
Inhibits thyroid hormone synthesis and blocks peripheral conversion of T4 to T3, making it useful in thyroid storm.