Propylthiouracil
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propylthiouracil
(′prō·pəl¦thī·ō′yu̇r·ə′sil)
(pharmacology) C7H10N2OS White, crystalline powder with a melting point of 218-221°C; soluble in ammonia and alkali hydroxides; used in medicine.
Drug Info:
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Propylthiouracil, PTU
Chemical formula:
- Drug Forms:
- Propylthiouracil, PTU tablets (below)
- Propylthiouracil Oral tablet
Propylthiouracil, PTU tablets
What are propylthiouracil tablets?
PROPYLTHIOURACIL (PTU) prevents the thyroid gland from producing too much thyroid hormone. Propylthiouracil is used to treat a condition known as hyperthyroidism (over-active thyroid). Generic propylthiouracil tablets are available.What should I tell my health care provider before I take this medicine?
They need to know if you have any of these conditions:• blood disorder
• liver disease
• an unusual or allergic reaction to propylthiouracil, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding
How should I take this medicine?
Take propylthiouracil tablets by mouth. Follow the directions on the prescription label. Swallow the tablets with a drink of water. Take your doses at regular intervals. Do not take your medicine more often than directed.What if I miss a dose?
If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.What drug(s) may interact with propylthiouracil?
• amiodarone• digoxin
• potassium iodide
• sodium iodide
• theophylline
• thyroid hormones
• warfarin
Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Check with your health care professional before stopping or starting any of your medicines.
What should I watch for while taking propylthiouracil?
Visit your prescriber or health care professional for regular checks on your progress, and to make sure your body is producing the right amount of thyroid hormone.If you are going to have surgery, tell your prescriber or health care professional that you are taking propylthiouracil.
Propylthiouracil, like other antithyroid agents, has the potential to reduce your resistance to infection. Contact your prescriber or health care professional if you have any infection or injury. Do not have any vaccinations without your prescriber's approval.
What side effects may I notice from taking propylthiouracil?
Side effects that you should report to your prescriber or health care professional as soon as possible:• backache
• black, tarry stools
• decrease in the amount of urine passed
• fever, sore throat, hoarseness
• goiter (enlarged thyroid gland causing swelling in the throat)
• menstrual changes
• mouth sores
• numbness or tingling in the hands or feet
• severe redness or itching of the skin
• stomach pain
• swelling of the feet or legs
• unusual bleeding or bruising, red spots on the skin
• unusual or sudden weight gain
• unusual tiredness or weakness
• yellowing of skin or eyes
Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
• fever
• muscle aches and pains
• nausea, vomiting
• skin rashes, itching
Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot open.Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Keep container tightly closed. Throw away any unused medicine after the expiration date.
Last updated: 7/1/2002
Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.
Oxford A-Z of Medicinal Drugs:
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propylthiouracil
An antithyroid drug similar to carbimazole. It is used to treat thyrotoxicosis (overproduction of thyroid hormones) and also to reduce hormone concentrations before surgery to remove part of an overactive thyroid gland. Propylthiouracil is available as tablets on prescription only.
Side effects and precautions:
see carbimazole.
| proprietary name, propranolol hydrochloride, propiverine hydrochloride | |
| prostaglandins, protamine sulphate, prothrombin complex |
Word Tutor:
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propylthiouracil
IN BRIEF: n. - A crystalline compound used as an antithyroid drug in the treatment of goiter.
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Saunders Veterinary Dictionary:
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propylthiouracil
A thyroid inhibitor used in the treatment of hyperthyroidism, but because of severe hematologic toxicity in cats other drugs are preferred.
Mosby's Dental Dictionary:
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propylthiouracil
n
PTU
trade name: generic; drug class: thyroid hormone antagonist; action: blocks synthesis of thyroid hormones T 3(triiodothyronine), T4 (thyroxine); uses: preparation for thyroidectomy, thyrotoxic crisis, hyperthyroidism, thyroid storm.
Wikipedia on Answers.com:
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Propylthiouracil
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| Systematic (IUPAC) name | |
| 6-propyl-2-sulfanylpyrimidin-4-one | |
| Clinical data | |
| AHFS/Drugs.com | monograph |
| MedlinePlus | a682465 |
| Pregnancy cat. | D |
| Legal status | ? |
| Routes | Oral |
| Pharmacokinetic data | |
| Bioavailability | 80%-95% |
| Metabolism | ? |
| Half-life | 2 hours |
| Excretion | ? |
| Identifiers | |
| CAS number | 51-52-5  |
| ATC code | H03BA02 |
| PubChem | CID 657298 |
| DrugBank | DB00550 |
| ChemSpider | 571424 |
| UNII | 721M9407IY |
| KEGG | D00562 |
| ChEBI | CHEBI:8502 |
| ChEMBL | CHEMBL1518 |
| Chemical data | |
| Formula | C7H10N2OS |
| Mol. mass | 170.233 g/mol |
| SMILES | eMolecules & PubChem |
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Propylthiouracil (PTU) or 6-n-Propylthiouracil[1] (PROP) is a thioamide drug used to treat hyperthyroidism (including Graves' disease) by decreasing the amount of thyroid hormone produced by the thyroid gland.[2] Its notable side effects include a risk of agranulocytosis.
On 3 June 2009, the FDA published an alert "notifying healthcare professionals of the risk of serious liver injury, including liver failure and death, with the use of propylthiouracil."[3] As a result, propylthiouracil is no longer recommended in non-pregnant adults and in children as the front line antithyroid medication[4].
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Contents
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History
It was approved by the US Food and Drug Administration in 1947.
Mode of action
Central
PTU inhibits the enzyme thyroperoxidase, which normally acts in thyroid hormone synthesis by oxidizing the anion iodide (I-) to iodine (I0), facilitating iodine's addition to tyrosine residues on the hormone precursor thyroglobulin. This is one of the essential steps in the formation of thyroxine (T4).[5]
PTU does not inhibit the action of the sodium-dependent iodide transporter located on follicular cells' basolateral membranes. Inhibition of this step requires competitive inhibitors, such as perchlorate and thiocyanate.
Peripheral
PTU also acts by inhibiting the enzyme 5'-deiodinase (tetraiodothyronine 5' deiodinase), which converts T4 to the active form T3. (This is in contrast to methimazole, which shares propylthiouracil's central mechanism, but not its peripheral one.)
Pharmacokinetics
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.[6]
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.
Side effects
One possible side effect is agranulocytosis,[7] 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.
A more life threatening side effect is sudden, severe, fulminant hepatic failure resulting in death or 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 [4]
Propylthiouracil is generally well-tolerated, with side effects occurring in one of every 100 patients. The most common side effects are related to the skin, and include rash, itching, hives, abnormal hair loss, and skin pigmentation. Other common side effects are swelling, nausea, vomiting, heartburn, loss of taste, joint or muscle aches, numbness and headache, allergic reactions, and hair whitening.
Propylthiouracil in pregnancy
Propylthiouracil is classified as Drug Class D in pregnancy. Class D signifies there is positive evidence of human fetal risk. Maternal benefit may outweigh fetal risk in life-threatening situations.[8] PTU is preferred over methimazole (which is also a class D) only in the first trimester of pregnancy and in woman who may become pregnant. In the second and third trimester, methimazole is preferred[4].
The primary effect on the fetus from transplacental passage of PTU is the production of a mild hypothyroidism when the drug is used close to term. This usually resolves within a few days without treatment. The hypothyroid state may be observed as a goiter in the newborn, and is the result of increased levels of fetal pituitary thyrotropin. The incidence of fetal goiter after PTU treatment in reported cases is approximately 12%.[9]
Chemical structure
Anderson, George W.; Halverstadt, I. F.; Miller, Wilbur H.; Roblin, Richard O. (1945). "Studies in Chemotherapy. X. Antithyroid Compounds. Synthesis of 5- and 6- Substituted 2-Thiouracils from β-Oxoesters and Thiourea". Journal of the American Chemical Society 67 (12): 2197. doi:10.1021/ja01228a042.
References
- ^ The letter "n" should be a lower case letter, as it describes the nature of the propyl substituent as normal, rather than its position on one of the ring nitrogens. Thereby, the position already is marked by the "6".
- ^ Nakamura H, Noh JY, Itoh K, Fukata S, Miyauchi A, Hamada N (June 2007). "Comparison of methimazole and propylthiouracil in patients with hyperthyroidism caused by Graves' disease". The Journal of Clinical Endocrinology and Metabolism 92 (6): 2157–62. doi:10.1210/jc.2006-2135. PMID 17389704. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=17389704.
- ^ "Propylthiouracil (PTU)-Induced Liver Failure". FDA. http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/DrugSafetyInformationforHeathcareProfessionals/ucm162701.htm. Retrieved 2009-05-03.
- ^ a b c Bahn RS, Burch HS, Cooper DS, et al. (July 2009). "The Role of Propylthiouracil in the Management of Graves' Disease in Adults: report of a meeting jointly sponsored by the American Thyroid Association and the Food and Drug Administration". Thyroid 19 (7): 673–4. doi:10.1089/thy.2009.0169. PMID 19583480. http://www.liebertonline.com/doi/pdf/10.1089/thy.2009.0169.
- ^ Boron, WF & Boulpaep, EL. 2005. Medical Physiology, Updated Edition. Elsevier Saunders, Philadelphia, PA
- ^ Abalovich M, Amino N, Barbour LA, et al. (August 2007). "Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society Clinical Practice Guideline". J. Clin. Endocrinol. Metab. 92 (8 Suppl): S1–47. PMID 17948378. http://jcem.endojournals.org/cgi/content/full/92/8_suppl/s1?maxtoshow=&hits=10&RESULTFORMAT=&author1=abalovich&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT#SEC6.
- ^ Cho YY, Shon HS, Yoon HD (December 2005). "Management of a pregnant patient with Graves' disease complicated by propylthiouracil induced agranulocytosis". The Korean journal of internal medicine 20 (4): 335–8. PMID 16491833. http://www.kaim.or.kr/journal/view2.php?year=2005&vol=20&no=4&page=335.
- ^ propylthiouracil
- ^ Propylthiouracil: Drug safety during pregnancy and breastfeeding / DRUGSAFETYSITE.COM
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