As a result, propylthiouracil is no longer recommended in non-pregnant adults and in children as the front line antithyroid medication.One possible side effect is agranulocytosis, a decrease of white blood cells in the blood. Symptoms and signs of agranulocytosis include infectious lesions of the throat, the gastrointestinal tract, and skin with an overall feeling of illness and fever. A decrease in blood platelets (thrombocytopenia) also may occur. Since platelets are important for the clotting of blood, thrombocytopenia may lead to problems with excessive bleeding. Side effects are suspected and the drug is sometimes discontinued if the patient complains of recurrent episodes of sore throat. Another life-threatening side effect is sudden, severe, fulminant liver failure resulting in death or the need for a liver transplantation, which occurs in up to 1 in 10,000 people taking propylthiouracil. Unlike agranulocytosis which most commonly occurs in the first three months of therapy, this side effect may occur at any time during treatment. Pregnancy
Propylthiouracil is classified as Drug Class D in pregnancy. Class D signifies there is positive evidence of human fetal risk. The maternal benefit may outweigh fetal risk in life-threatening situations. PTU is preferred over methimazole (which is also a class D) only in the first trimester of pregnancy and in women who may become pregnant because of the increased risk of teratogenicity of methimazole during critical organogenesis.
For information on that enzyme family, see Iodotyrosine deiodinase. Pharmacokinetics
The administration is oral, with peak serum concentrations occurring in one hour, and actively concentrated to the thyroid gland. Depending on several patient variables, however, euthyroid status may not be achieved until 2–4 months after treatment initiation. Of note, the drug is approximately 70% protein-bound and significantly ionized at normal physiologic pH, while the antithyroid agent methimazole is substantially less protein bound. However, both are equally transferred across the placenta.The plasma half-life is one hour and is not altered appreciably by the thyroid status of the patient. Due to the concentration in the thyroid, however, dosing intervals may last 8 hours or longer. Less than 10% of the drug is excreted unchanged, with the remaining fraction undergoing extensive hepatic metabolism via glucuronidation. Chemical synthesis
Propylthiouracil can be prepared from ethyl 3-oxohexanoate and thiourea. Role in taste
Propylthiouracil, together with phenylthiocarbamide (PTC), are known to have bitter taste. However, it seems the propensity for tasting these compounds is genetically based and the bitter taste is likely to be engendered by the thiocyanate moiety, also present in PTC. History
It was approved by the United States Food and Drug Administration in 1947. References
External links

"Propylthiouracil". Drug Information Portal. U.S. National Library of Medicine.