PROPYLTHIOURACIL (PTU) 
(proe-pill-thye-oh-yoor'a-sill)
Propyl-Thyracil 
Classifications: hormones and synthetic substitutes; antithyroid agent
Pregnancy Category: D
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50 mg tablets
Interferes with use of iodine and blocks synthesis of thyroxine (T4) and triiodothyronine (T3). Does not interfere with release and utilization of stored thyroid hormone; thus antithyroid action is delayed days and
weeks until preformed T3 and T4 are degraded.
Drug-induced hormone reduction results in compensatory release of thyrotropin (TSH), which causes marked hyperplasia and vascularization
of thyroid gland. With good adherence to drug regimen, chemical euthyroidism can be achieved 6–12 wk after start of therapy.
Hyperthyroidism, iodine-induced thyrotoxicosis, and hyperthyroidism associated with thyroiditis; to establish euthyroidism
prior to surgery or radioactive iodine treatment; palliative control of toxic nodular goiter.
Last trimester of pregnancy (category D), lactation; concurrent administration of sulfonamides or coal tar derivatives such
as aminopyrine or antipyrine.
Infection; concomitant administration of anticoagulants or other drugs known to cause agranulocytosis; bone marrow depression;
impaired liver function.
Hyperthyroidism
Adult: PO 300–450 mg/d divided q8h, may need 600–1200 mg/d initially
Geriatric: PO 150–300 mg/d divided q8h
Child: PO 6–10 y, 50–150 mg/d; >10 y, 150–300 mg/d or 150 mg/m2/d
Neonates: PO 5–10 mg/kg/d
Thyrotoxic Crisis
Adult: PO 200 mg q4–6h until full control achieved
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- Give at the same time each day with relation to meals. Food may alter drug response by changing absorption rate.
- If drug is being used to improve thyroid state before radioactive iodine (RAI) treatment, discontinued 3 or 4 d before treatment
to prevent uptake interference. PTU therapy may be resumed if necessary 3–5 d after the RAI administration.
- Store drug at 15°–30° C (59°–86° F) in light resistant container.
CNS: Paresthesias, headache, vertigo, drowsiness, neuritis. GI: Nausea, vomiting, diarrhea, dyspepsia, loss of taste, sialoadenitis, hepatitis. Hematologic: Myelosuppression, lymphadenopathy, periarteritis, hypoprothrombinemia, thrombocytopenia, leukopenia, agranulocytosis. Metabolic: Hypothyroidism (goitrogenic): Enlarged thyroid, reduced GI motility, periorbital edema, puffy hands and feet, bradycardia,
cool and pale skin, worsening of ophthalmopathy, sleepiness, fatigue, mental depression, dizziness, vertigo, sensitivity to
cold, paresthesias, nocturnal muscle cramps, changes in menstrual periods, unusual weight gain. Skin: Skin rash, urticaria, pruritus, hyperpigmentation, lightening of hair color, abnormal hair loss. Body as a Whole: Drug fever, lupus-like syndrome, arthralgia, myalgia, hypersensitivity vasculitis.
Propylthiouracil may elevate prothrombin time and serum alkaline phosphatase, AST, ALT levels.
Drug: Amiodarone, potassium iodide, sodium iodide, thyroid hormones can reverse efficacy.
Absorption: Rapidly absorbed from GI tract. Peak: 1–1.5 h. Distribution: Appears to concentrate in thyroid gland; crosses placenta; some distribution into breast milk. Metabolism: Rapidly metabolized to inactive metabolites. Elimination: 35% excreted in urine within 24 h. Half-Life: 1–2 h.
Assessment & Drug Effects
- Be aware that about 10% of patients with hyperthyroidism have leukopenia <4000 cells/mm3 and relative granulopenia.
- Observe for signs of clinical response to PTU (usually within 2 or 3 wk): Significant weight gain, reduced pulse rate, reduced
serum T4.
- Lab tests: Baseline and periodic T3 and T4; periodic CBC with differential and platelet count.
- Satisfactory euthyroid state may be delayed for several months when thyroid gland is greatly enlarged.
- Be alert to signs of hypoprothrombinemia: Ecchymoses, purpura, petechiae, unexplained bleeding. Warn ambulatory patients to
report these signs promptly.
- Be alert for important diagnostic signs of excess dosage: Contraction of a muscle bundle when pricked, mental depression,
hard and nonpitting edema, and need for high thermostat setting and extra blankets in winter (cold intolerance).
- Monitor for urticaria (occurs in 3–7% of patients during weeks 2–8 of treatment). Report severe rash.
Patient & Family Education
- Note that PTU treatment may be reinstituted if surgery fails to produce normal thyroid gland function.
- Be aware that thyroid hormone may be given concomitantly with PTU throughout pregnancy to prevent hypothyroidism in mother
with little effect on fetus.
- Report severe skin rash or swelling of cervical lymph nodes. Therapy may be discontinued.
- Report to physician sore throat, fever, and rash immediately (most apt to occur in first few months of treatment). Drug will
be discontinued and hematologic studies initiated.
- Avoid use of OTC drugs for asthma, or cough treatment without checking with the physician. Iodides sometimes included in such
preparations are contraindicated.
- Learn how to take pulse accurately and check daily. Report to physician continued tachycardia.
- Report diarrhea, fever, irritability, listlessness, vomiting, weakness; these are signs of inadequate therapy or thyrotoxicosis.
- Chart weight 2 or 3 times weekly; clinical response is monitored through changes in weight and pulse.
- Continue monitoring and recording weight and pulse rate while in remission. Report onset of tremor, anxiety state, gradual
ascending pulse rate, and loss of weight to physician (signs of hormone deficiency).
- Do not alter drug regimen (e.g., increase, decrease, omit doses, change dosage intervals).
- Check with physician about use of iodized salt and inclusion of seafood in the diet.
- Do not breast feed while taking this drug.
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