Indications And Clinical Uses: The medical management of hyperthyroidism. The treatment of thyrotoxicosis prior to surgery. In conjunction with radioiodine to hasten recovery while awaiting the effects of radiation. The management of thyroid storm in addition to other therapeutic measures.
Contra-Indications: Lactation. Hypersensitivity or idiosyncratic reaction to propylthiouracil.
Manufacturers’ Warnings In Clinical States: Pregnancy: Propylthiouracil readily crosses the placenta and can cause goiter or cretinism in the developing fetus. Thyroid does not cross the placenta to a degree significant enough to protect the fetus against the effects of propylthiouracil. If used for the management of thyrotoxicosis during pregnancy, propylthiouracil should be used in the smallest possible dose.
Precautions: The dose of propylthiouracil should be reduced or temporarily discontinued if signs of hypothyroidism occur during treatment.
Blood formula should be determined prior to institution of treatment. Patients receiving propylthiouracil should be advised to notify their physician if fever, sore throat, unusual bleeding or bruising, or skin rash occurs. In such cases, white blood cell and differential counts should be made to determine whether severe leukopenia or agranulocytosis has developed.
Propylthiouracil has occasionally been reported to cause hypoprothrombinemia which would increase the effect of anticoagulants. Doses of oral anticoagulants, administered concurrently, should be adjusted accordingly.
The vascularity and size of the thyroid gland may increase during treatment with propylthiouracil. This suggests overtreatment and indicates the need for reduced dosage.
When propylthiouracil is administered pre-operatively, iodine, in the form of a strong iodine solution (Lugol’s solution or potassium iodide solution) should be given concomitantly for 7 to 10 days prior to surgery. The rationale for this is to reduce the vascularity and fragility of the thyroid gland.
Adverse Reactions: Blood: Agranulocytosis is the most serious potential side effect. The incidence is less than 0.5%. It usually develops in the first few months of therapy, is dose related and is reversible on rapid withdrawal of the drug.
Leukopenia with granulocytopenia, hemolytic anemia, thrombocytopenia, hypoprothrombinemia with hemorrhagic manifestations, aplastic anemia, myeloblastic leukemia and hyperglobulinemia have been reported.
Skin: Urticaria, pruritus and a mild papular rash which may be accompanied by purpura are the most common skin reactions (about 3%).
Loss or depigmentation of the hair are less frequent.
Two cases of vesicular eruption in the newborn have been reported, secondary to maternal propylthiouracil therapy.
Miscellaneous: Nausea, vomiting, abdominal discomfort, drowsiness, headache, dizziness, arthralgia and paresthesia occur occasionally.
Very Rare Reactions: Drug fever, lymphadenopathy, splenomegaly, hepatitis, cholestatic jaundice, neuritis, nephritis, sialadenopathy, recurrent keratitis, conjunctival disorders, connective tissue disorders resembling polyarteritis, arthritis, lupus erythematosus and an ototoxic reaction presenting as unilateral sensorineural hearing impairment.
Symptoms And Treatment Of Overdose: Symptoms and Treatment: Acute poisoning with propylthiouracil has not been reported.
Overdosage can result in enlargement of the thyroid gland, with signs and symptoms of hypothyroidism. This can be readily reversed by reducing or even temporarily withdrawing medication. Thyroxine replacement therapy, until the patient becomes euthyroid, may be indicated.
Overdosage in pregnant women may result in congenital goiter and hypothyroidism in the fetus. The newborn child should be examined carefully for signs of hypothyroidism and immediate thyroid therapy should be instituted if hypothyroidism is confirmed.
Hemorrhage may be controlled by the administration of vitamin K1 and the dosage of propylthiouracil should be reduced.
Dosage And Administration: Treatment should be individualized, according to the severity of symptoms and signs of hyperthyroidism and response to therapy.
Adults: The recommended initial dose is 50 to 100 mg every 8 hours, with increases as necessary up to a maximum of 500 mg/day. In some cases, initial doses as high as 900 mg/day may be required.
When doses larger than 300 mg/day are needed, the drug should be administered every 4 to 6 hours.
Usually after one or 2 weeks, but certainly after 3 weeks of therapy, objective signs of clinical improvement should be seen.
Delayed responses are sometimes noted when the thyroid is unusually large and when iodine in any form has previously been given.
The patient should be examined regularly by the physician and the dose adjusted until the patient is euthyroid (usually after 6 to 8 weeks). At this stage, the dose should be reduced by 33% every 4 to 6 weeks to a maintenance dose of 50 mg 2 or 3 times daily, administered at regular intervals.
The course of therapy may last from 6 months to 3 years. Usually within 1 to 2 years, a prolonged remission in 50% of the cases can be expected.
When remission is observed, propylthiouracil should be withdrawn over a period of 1 to 2 months under close supervision.
Children: Initial Dose Guideline: 150 mg/m24 hours.
For Children 10 Years of Age and Older: 150 to 300 mg/day in divided doses, at regular intervals.
For Children 6 to 10 Years of Age: 50 to 150 mg/day in divided doses, at regular intervals.
General Maintenance Dose: 50 mg twice daily when euthyroid.
Renal Failure: The following schedule is recommended.
SuppliedSupplied: Each white, phi-marked, scored tablet contains: propylthiouracil 50 or 100 mg. Gluten-, lactose- and tartrazine-free. Bottles of 100.
PROPYL-THYRACIL® Frosst Propylthiouracil Hyperthyroidism Therapy