Propyl thiouracil
Propylthiouracil , is one of the thiocarbamide compounds. It is an antithyroid drug administered orally.
Mechanism of effect
Exact mechanism(s) not fully elucidated; however, propylthiouracil may interfere with the oxidation of iodide ion and iodotyrosyl groups.
Propylthiouracil inhibits the conversion of thyroxine to triiodothyronine in peripheral tissues and inhibits the synthesis of thyroid hormones.
Pharmacodynamic
Inhibits the synthesis of thyroid hormones by interfering with the incorporation of iodine into tyrosyl residues of thyroglobulin; also inhibits the coupling of these iodotyrosyl residues to form iodothyronine.
Pharmacokinetics
Propylthiouracil is readily absorbed and is extensively metabolized. Bioavailability is approximately 75%. Approximately 35% of the drug is excreted in the urine, in intact and conjugated forms, within 24 hours.
Dosage
Usual Adult Dose for Hyperthyroidism
INITIAL DOSE : 100 mg orally every 8 hours (300 mg daily); some patients may require 400 mg orally daily in 3 divided doses; rarely, a patient may require 600 to 900 mg orally daily in 3 divided doses
MAINTENANCE DOSE : 100 to 150 mg orally daily in 3 equally divided doses every 8 hours
Usual Adult Dose for Thyroid Storm
INITIAL DOSE : 100 mg orally every 8 hours (300 mg daily); some patients may require 400 mg orally daily in 3 divided doses; rarely, a patient may require 600 to 900 mg orally daily in 3 divided doses
MAINTENANCE DOSE : 100 to 150 mg orally daily in 3 equally divided doses every 8 hours
Usual Pediatric Dose for Hyperthyroidism
This drug is generally not recommended for use in pediatric patients except when other therapies are not an option.
SUGGESTED INITIAL DOSE :
-Patients younger than 6 years: Not recommended
-Patients 6 years or older: 50 mg orally daily with careful upward titration based on clinical response and evaluation of TSH and free T4 levels
Drug contraindications
hypersensitivity to this drugAlerts
• Liver injury resulting in liver failure, liver transplantation, or death, has been reported with Propylthiouracil therapy in adult and pediatric patients .
• Biochemical monitoring of liver function (bilirubin, alkaline phosphatase) and hepatocellular integrity (ALT, AST) is not expected to attenuate the risk of severe liver injury due to its rapid and unpredictable onset. Patients should be informed of the risk of liver failure.
• Patients should be instructed to report any symptoms of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.), particularly in the first six months of therapy.
• When these symptoms occur, Propylthiouracil should be discontinued immediately and liver function tests and ALT and AST levels obtained.
• There are cases of liver injury, including liver failure and death, in women treated with Propylthiouracil during pregnancy.
• Two reports of in utero exposure with liver failure and death of a newborn have been reported. If Propylthiouracil is used during pregnancy, or if the patient becomes pregnant while taking Propylthiouracil, the patient should be warned of the rare potential hazard to the mother and fetus of liver damage.
• Propylthiouracil crosses the placenta and can cause fetal goiter and cretinism when administered to a pregnant woman. After the first trimester of pregnancy, the use of an alternative antithyroid medication may be advisable.
• Agranulocytosis occurs in approximately 0.2% to 0.5% of patients and is a potentially life-threatening side effect of Propylthiouracil therapy. Agranulocytosis typically occurs within the first 3 months of therapy.
• Propylthiouracil can cause hypothyroidism necessitating routine monitoring of TSH and free T4 levels with adjustments in dosing to maintain a euthyroid state. Because the drug readily crosses placental membranes, Propylthiouracil can cause fetal goiter and cretinism when administered to a pregnant woman.
Points of recommendation
To make sure this medicine is safe for you, tell your doctor if you have :
• If you have an allergy to propylthiouracil or any other part of this medicine.
• If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching ; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs .
Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect :
• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
• Signs of infection like fever, chills, very bad sore throat, ear or sinus pain, cough, more sputum or change in color of sputum, pain with passing urine, mouth sores, or wound that will not heal.
• You may bleed more easily. Be careful and avoid injury. Use a soft toothbrush and an electric razor.
• If you are taking warfarin, talk with your doctor. You may need to have your blood work checked more closely while you are taking it with propylthiouracil .
• This medicine may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking this medicine, call your doctor right away.
• Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.
• Take a missed dose as soon as you think about it. If it is close to the time for your next dose, skip the missed dose and go back to your normal time. Do not take 2 doses at the same time or extra doses.
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