Propylthiouracil (PTU)

A to Z Drug Facts

(pro-puhl-thigh-oh-YOU-rah-sill)

Propyl-Thyracil

Class: Antithyroid

 Action Inhibits synthesis of thyroid hormones.

 Indications Long-term therapy of hyperthyroidism; amelioration of hyperthyroidism in preparation for subtotal thyroidectomy or radioactive iodine therapy; when thyroidectomy is contraindicated or not advisable. Unlabeled use(s): Management of alcoholic liver disease.

 Contraindications Hypersensitivity to antithyroid drugs; lactating women.

 Route/Dosage

ADULTS: PO Initial dose: 300 mg/day in 3 equal doses q 8 hr. In patients with severe hyperthyroidism or very large goiters, initial dose is usually 400 mg/day, occasionally up to 600 to 900 mg/day. Maintenance: 100 to 150 mg/day in divided doses q 8 hr. CHILDREN > 10 YR: PO Initial dose: 150 to 300 mg/day in divided doses q 8 hr. Maintenance: Determined by response. CHILDREN 6 to 10 YR: PO Initial dose: 50 to 150 mg/day in divided doses q 8 hr. ALTERNATE DOSING FOR CHILDREN: PO Initial dose: 5 to 7 mg/kg/day in divided doses q 8 hr. Maintenance: – initial dose, beginning when patient is euthyroid.

 Interactions

Anticoagulants: Altered anticoagulant action. Beta blockers: Increased effects of beta blockers. Digitalis glycosides: Increased digitalis levels, resulting in toxicity. Theophylline: Altered theophylline clearance in hyperthyroid or hypothyroid patients.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Paresthesias; neuritis; headache; vertigo; drowsiness; neuropathies; CNS stimulation; depression. DERM: Rash; urticaria; pruritus; erythema nodosum; skin pigmentation; exfoliative dermatitis; lupus-like syndrome (splenomegaly, hepatitis, periarteritis; hypoprothrombinemia; bleeding). EENT: Loss of taste; sialadenopathy. GI: Nausea; vomiting; epigastric distress. GU: Nephritis. HEPA: Jaundice; hepatitis. HEMA: Inhibition of myelopoiesis (eg, agranulocytosis, leukopenia, granulocytopenia, thrombocytopenia); aplastic anemia; hypoprothrombinemia; periarteritis. OTHER: Abnormal hair loss; arthralgia; myalgia; edema; lymphadenopathy; drug fever; interstitial pneumonitis; insulin autoimmune syndrome (hypoglycemia).

 Precautions

Pregnancy: Category D. Lactation: Avoid nursing. However, if antithyroid drug is essential, PTU is preferred antithyroid agent while nursing. Children: Hepatotoxicity has occurred in pediatric patients. Discontinue drug immediately if signs and symptoms of hepatic dysfunction develop. Agranulocytosis: Potentially most serious side effect. Discontinue drug if agranulocytosis, aplastic anemia, hepatitis, fever, or exfoliative dermatitis occur. Hemorrhagic effects: May cause hypoprothrombinemia and bleeding.

 Administration/Storage

• Give with meals to minimize GI irritation.
• Administer q 8 hr to maintain serum drug levels.
• Encourage fluid intake of 3 to 4 L/day, unless contraindicated.
• Store in tight, light-resistant container at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Obtain baseline weight, BP, body temperature and pulse rate and monitor periodically during therapy.
• Ensure that baseline thyroid function has been evaluated prior to therapy and reassess q 2 to 3 mo during therapy.
• Determine baseline WBC count and differential before administration and monitor for agranulocytosis during first 3 mo of therapy.
• Monitor I&O and check for edema.
• Before discharge, obtain dietary consult for patient regarding iodine intake; shellfish and iodine-containing foods may be restricted.
• Assess for signs of hypoprothrombinemia; monitor prothrombin time during therapy, especially during surgical procedures.
• Assess patient for development and tolerance of symptoms of hyperthyroidism or hypothyroidism.
• If symptoms of hypersensitivity occur (eg, swollen lymph nodes, skin eruption or itching), notify physician. Drug may be discontinued.

 Patient/Family Education

• Instruct patient to take resting pulse daily and encourage patient to keep recorded chart.
• Advise patient to monitor weight at least 2 to 3 times/wk or per physician instruction, obtaining weight at same time, using same scale. Encourage patient to keep recorded chart.
• Emphasize importance of following dietary restrictions regarding shellfish, iodized salt and other foods high in iodine.
• Explain that desired response may take several months if the thyroid is greatly enlarged.
• Advise patient to carry Medi-Alert identification at all times describing medications.
• Instruct patient to notify dentist or physician of drug regimen before surgical or dental procedures.
• Emphasize importance of follow-up visits to monitor effectiveness of drug therapy.
• Caution patient not to stop taking medication abruptly to avoid thyroid crisis.
• Instruct patient to report the following symptoms to physician: Sore throat, fever, rash, mouth sores; cold intolerance, mental depression; tachycardia, irritability; persistent nausea, steatorrhea or vomiting, drowsiness, yellowing of skin or whites of eyes; unusual bleeding or bruising.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other activities requiring mental alertness.
• Instruct patient not to take otc medications without consulting physician.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts