thiamazole

Action and Spectrum

Actions and Spectrum: 

thiamazole is a medication commonly used to treat hyperthyroidism, in which the thyroid gland generally produces an excess amount of thyroid hormone. thiamazole works by inhibiting the production of thyroid hormones in the thyroid gland. Here’s an overview of its action and spectrum of use: 

Action: 

Inhibition of Thyroid Hormone Production: thiamazole works primarily by interfering with the synthesis of the thyroid hormones in the thyroid gland. It does this by inhibiting the enzyme thyroperoxidase, essential for the iodination and coupling of thyroid hormone precursors (thyroglobulin). 

Spectrum: 

Hyperthyroidism: thiamazole is primarily used to treat hyperthyroidism, a condition where the thyroid gland is typically overactive and also produces excessive amounts of thyroid hormones (thyroxine or T4 and triiodothyronine or T3). Hyperthyroidism can be caused by various conditions, including Graves’ disease, toxic multinodular goiter, and thyroiditis. 

Preparation for Thyroid Surgery or Radioactive Iodine Treatment: thiamazole may also be used to prepare patients with hyperthyroidism for thyroid surgery or radioactive iodine therapy. Normalizing thyroid hormone levels before these treatments reduces the risk of thyroid storm (a severe and potentially life-threatening form of hyperthyroidism) during and after the procedures. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Dysgeusia 

Bleeding 

Pancreatitis 

Hypoprothrombinaemia 

Dermatologic reactions 

Acute salivary gland swelling 

Lupus-like syndrome 

Thrombocytopenia 

Nausea 

Insulin autoimmune syndrome 

Hepatotoxicity including acute liver failure 

Hypothyroidism 

Vertigo 

Vasculitis resulting in severe complications 

Aplastic anaemia 

Ageusia 

Leucopenia 

Drug fever 

Periarteritis 

Vomiting 

Epigastric distress 

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

Contraindication 

• Hypersensitivity or Allergy: thiamazole should not be used in individuals with a known hypersensitivity or allergy to the drug or its components. Allergic reactions can be severe and include symptoms such as skin rash, itching, swelling, severe dizziness, or difficulty breathing. 
• Agranulocytosis: thiamazole can rarely cause a serious condition called agranulocytosis, a severe reduction in white blood cell count. This can leads to a weakened immune system and increase the risk of infections. If a patient has a history of agranulocytosis or other blood disorders, thiamazole should generally be avoided. 
• Pregnancy and Breastfeeding: The use of thiamazole during pregnancy and breastfeeding requires careful consideration. It is generally not recommended during the first trimester of pregnancy because it may be associated with an increased risk of congenital abnormalities. In the second and third trimesters, it may be used under the supervision of a healthcare provider when the benefits outweigh the potential risks. It can also be excreted in breast milk, so its use while breastfeeding should be discussed with a healthcare provider. 
• Liver Disease: thiamazole may affect liver function, and its use should be cautious in individuals with preexisting liver disease. Liver function should be generally monitored regularly during treatment with thiamazole. 
• Bone Marrow Disorders: Individuals with preexisting bone marrow disorders or conditions affecting blood cell production may be at increased risk of hematological side effects, including agranulocytosis. 
• Children Under 2 Years Old: thiamazole is generally not recommended for use in children under 2, except in particular cases under close medical supervision. 
• Interactions with Other Medications: thiamazole can interact with certain medications, so healthcare providers need to be aware of all the drugs, supplements, and herbal products a patient is taking to assess potential drug interactions. 

Caution 

• Regular Monitoring: A healthcare provider should closely monitor patients taking thiamazole. This includes regular thyroid function checks, typically through blood tests to measure thyroid hormone levels, to ensure that the medication effectively controls hyperthyroidism and that hormone levels are within the normal levels. 
• Initial Dosing: The initial dose of thiamazole should be carefully calculated based on the severity of hyperthyroidism. Starting with a low dose and gradually enhancing it as needed can help minimize side effects and improve tolerability. 
• Long-Term Use: thiamazole is often used as a long-term maintenance treatment for hyperthyroidism. Patients should be aware that they may need to take this medication for an extended period or indefinitely, depending on their condition. 
• Side Effects: Patients should be informed about potential side effects of thiamazole, including skin rash, upset stomach, changes in taste perception, and mild joint pain. If any unusual or severe side effects occur, they should be reported to the healthcare provider promptly. 
• Agranulocytosis Monitoring: Although rare, thiamazole can cause a severe condition called agranulocytosis, characterized by a significant decrease in white blood cell count. Individuals should be educated about the signs and symptoms of agranulocytosis, such as fever, sore throat, and mouth ulcers, and advised to seek immediate medical attention if these symptoms develop. 
• Liver Function: thiamazole can affect liver function in some individuals. Liver function tests should be conducted regularly during treatment to monitor for any liver-related side effects. 
• Children and Adolescents: thiamazole can be used in children and adolescents with hyperthyroidism, but dosing should be carefully calculated based on weight and age, and monitoring should be comprehensive. 
• Pregnancy and Breastfeeding: The use of thiamazole during pregnancy and breastfeeding should be discussed with a healthcare provider. Sometimes, it may be necessary to continue treatment to control hyperthyroidism while closely monitoring thyroid function and potential risks to the fetus or nursing infant. 
• Drug Interactions: Individuals should inform their healthcare provider about all medications, supplements, and herbal products they are taking to assess potential drug interactions. 
• Smoking Cessation: Smoking may decrease the effectiveness of thiamazole, so patients who smoke should be encouraged to quit or reduce smoking. 
• Patient Education: Individuals should be educated about the importance of adhering to their prescribed dosage regimen, attending follow-up appointments, and reporting any concerns or side effects to their healthcare provider. 

Pregnancy / Lactation

Pregnancy consideration:  

US FDA pregnancy category: Not assigned. 

Lactation:   

Excreted into human milk: Not known. 

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• <b>Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence, these categories of drugs need to be avoided by pregnant women.    
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

thiamazole is an antithyroid medication used in the pharmacological management of hyperthyroidism. It acts by inhibiting the enzyme thyroperoxidase, crucial for the iodination and coupling of thyroid hormone precursors (thyroglobulin). By interfering with these processes, thiamazole reduces the synthesis of thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), in the thyroid gland.

This leads to a decrease in the circulating levels of thyroid hormones, helping to normalize thyroid function in individuals with hyperthyroidism. thiamazole is typically administered orally, used as short-term preparation for thyroid surgery or radioactive iodine therapy, and as a long-term maintenance therapy to manage hyperthyroidism. Regular monitoring of the thyroid function is essential during its use to ensure effective control of hyperthyroidism and to adjust dosages as needed. 

Pharmacodynamics: 

Mechanism of action: The action of thiamazole is primarily centered around its ability to inhibit the production of thyroid hormones in thyroid gland. It is an antithyroid medication used to treat hyperthyroidism.  

Inhibition of Thyroid Hormone Synthesis: 

thiamazole interferes with the synthesis of thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3), in the thyroid gland. 

The thyroid gland produces typically these hormones through a series of steps, which involve iodination and coupling of iodinated amino acids within thyroglobulin, a protein in the thyroid follicles. 

thiamazole inhibits the enzyme thyroperoxidase (iodide peroxidase or TPO). This enzyme plays a crucial role in iodinating tyrosine residues on thyroglobulin and catalyzing the coupling of these iodinated tyrosine residues to form T4 and T3. 

Reduction in Thyroid Hormone Production: 

By inhibiting thyroperoxidase, thiamazole reduces the ability of the thyroid gland to generally produce T4 and T3. 

With the decreased synthesis of thyroid hormones, there is a decrease in the release of these hormones into the bloodstream. 

Feedback Loop Regulation: 

As thyroid hormone production is inhibited by thiamazole, the feedback loop involving the hypothalamus and pituitary gland is activated. 

Elevated TSH levels stimulate the thyroid gland to produce thyroid hormones, but thiamazole blocks their synthesis. 

Normalization of Thyroid Function: 

Over time, with thiamazole treatment, the feedback loop regulation may lead to reduced thyroid gland activity and a gradual decrease in thyroid hormone levels in the bloodstream. 

This normalization of thyroid function is the desired therapeutic outcome for individuals with hyperthyroidism. 

Pharmacokinetics: 

Absorption 

After ingestion, thiamazole is absorbed primarily in the gastrointestinal tract, particularly the small intestine.  

Distribution 

thiamazole has a high degree of plasma protein binding, primarily to albumin. This binding can limit its distribution to various tissues and organs. 

thiamazole is distributed throughout the body but has a particular affinity for the thyroid gland, where it exerts its antithyroid effects by inhibiting the production of thyroid hormones. 

Metabolism 

thiamazole is not significantly metabolized in the body. It is primarily excreted unchanged or with minimal metabolic transformation. 

Although it is not a significant site of metabolism for thiamazole, the liver may play a minor role in its biotransformation. 

Elimination and Excretion 

The kidneys primarily excrete thiamazole and its metabolites. Unchanged thiamazole and its metabolites may be eliminated in the urine. 

A small fraction of thiamazole may be excreted in the bile. 

Adminstartion

Administration: 

thiamazole is a medication commonly used to treat hyperthyroidism by inhibiting the production of thyroid hormones.  

• Dosage: The dosage of thiamazole varies depending on the severity of hyperthyroidism and the individual patient’s response. It is essential to follow the specific dosage prescribed by your healthcare provider. 
• Timing: thiamazole is usually taken once daily but can vary. It may be taken in the morning or evening, with or without food. Follow your healthcare provider’s instructions regarding the timing of your doses. 
• Consistency: Try to take thiamazole at the same time each day to maintain a consistent level of the medication in your bloodstream. 
• Swallow Whole: thiamazole tablets should be swallowed whole with a glass of water.  
• Follow Medical Instructions: Always follow the specific instructions your healthcare provider provides. They will determine the appropriate dosage and may adjust it based on your thyroid function test results. 
• Duration: thiamazole is often used as a long-term treatment for hyperthyroidism. The duration of therapy can vary from several months to years, depending on the underlying cause and your response to the medication. Do not stop taking thiamazole without consulting your healthcare provider, as abruptly discontinuing the medication can lead to a recurrence of hyperthyroidism. 
• Regular Monitoring: While on thiamazole, you will need regular monitoring of your thyroid function. This is typically done through blood tests to measure levels of thyroid hormones and also thyroid-stimulating hormone (TSH).  
• Adherence: It’s crucial to take thiamazole consistently as prescribed. Missing doses or taking them irregularly can affect the control of hyperthyroidism. 
• Report Side Effects: If you experience any side effects while taking thiamazole, such as skin rash, upset stomach, or changes in taste perception, report them to your healthcare provider. They can help manage side effects or adjust your treatment if necessary. 
• Pregnancy and Breastfeeding: Discuss this with your healthcare provider if you become pregnant or plan to breastfeed while taking thiamazole. They will weigh the risks and benefits and may need to adjust your treatment plan accordingly. 
• Smoking: If you smoke, consider quitting or reducing smoking, as smoking may decrease the effectiveness of thiamazole. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: thiamazole 

Why do we use thiamazole? 

thiamazole is a medication primarily used to treat hyperthyroidism, characterized through an overactive thyroid gland that generally produces excessive amounts of thyroid hormones (T3 and T4). thiamazole works by inhibiting the production of thyroid hormones in the thyroid gland.  

Hyperthyroidism Treatment: thiamazole is most commonly used to treat hyperthyroidism. It helps normalize thyroid hormone levels by diminishing the production of thyroid hormones in thyroid gland. Hyperthyroidism can be caused by various conditions, including: 

Graves’ Disease: An autoimmune disorder that generally causes the thyroid gland to become overactive. 

Toxic Multinodular Goiter: A condition where multiple nodules in the thyroid gland produce excessive hormones. 

Thyroiditis: Inflammation of the thyroid gland that generally lead to the release of excess thyroid hormones. 

Preparation for Thyroid Surgery or Radioactive Iodine Therapy: thiamazole is sometimes used to prepare individuals with hyperthyroidism for thyroid surgery or radioactive iodine treatment. Normalizing thyroid hormone levels before these procedures reduces the risk of complications such as thyroid storm (a severe form of hyperthyroidism) during and after the treatment. 

Maintenance Therapy: thiamazole can also be prescribed as a long-term maintenance therapy for individuals with hyperthyroidism to keep their thyroid hormone levels within the normal range.