dextrothyroxine

Action and Spectrum

Actions and spectrum: 

The action of dextrothyroxine is like that of levothyroxine. It functions as a replacement for endogenous thyroxine produced by thyroid gland and is essential for regulation of metabolism in the body. Thyroxine plays a crucial role in maintaining the body’s energy balance, growth, and development. 

• Metabolism Regulation: Like natural thyroxine, dextrothyroxine helps regulate the metabolic rate of cells and tissues in the body. This is important for maintaining energy balance and supporting various physiological processes. 
• Thyroid Hormone Replacement: Dextrothyroxine can be used as a replacement therapy in individuals with hypothyroidism, where thyroid gland does not produce the enough thyroid hormones. However, levothyroxine is more commonly prescribed for this purpose. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Abdominal pain 

Allergic reaction 

Diarrhea 

Skin rash 

Heart attack 

Increased sweating 

Insomnia 

Tremors 

Chest pain 

Hair loss 

Headache 

Increased body temperature 

Erythema 

Weight loss 

Arrhythmia 

Black Box Warning

Black Box Warning: 

There is no specific black box warning associated with dextrothyroxine. 

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

• Allergy or Hypersensitivity: Individuals with a known hypersensitivity or allergy to dextrothyroxine or any of its components should not use the medication. 
• Adrenal Insufficiency: Individuals with adrenal insufficiency may need careful monitoring and dosage adjustments when using thyroid hormones. 
• Thyroid Disorders: Dextrothyroxine may not be suitable for individuals with certain thyroid disorders, such as hyperthyroidism. The use of thyroid hormones inappropriately in such cases can exacerbate existing conditions. 
• Pregnancy and Breastfeeding: The use of thyroid hormones during pregnancy and breastfeeding requires careful consideration and monitoring. Thyroid hormone requirements can change during these periods, and adjustments to medication may be necessary.

Caution: 

• Cardiovascular Conditions: Thyroid hormones, including dextrothyroxine, can have effects on the cardiovascular system. Caution is typically advised in individuals with cardiovascular conditions such as angina, hypertension, or arrhythmias. Close monitoring may be necessary, and dosage adjustments might be required. 
• Elderly Patients: Individuals may be more sensitive to the effects of thyroid hormones. Careful monitoring and conservative dosing may be warranted. 
• Bone Health: Long-term use of thyroid hormones in excess may affect bone health, leading to decreased bone density. This is a consideration, particularly in postmenopausal women. 
• Other Medical Conditions: Individuals with certain medical conditions, such as diabetes or certain psychiatric disorders, may require special consideration when using thyroid hormones. The presence of these conditions may necessitate careful monitoring and potential adjustments in medication dosage.

Comorbidities: 

• Osteoporosis: Long-term use of thyroid hormones, especially in excess, may impact bone health and contribute to decreased bone density. This is a consideration, particularly in individuals at risk of osteoporosis. 
• Diabetes: Thyroid hormones can affect glucose metabolism, and individuals with diabetes may need careful monitoring of blood sugar levels when using thyroid hormone replacement therapy. 
• Psychiatric Disorders: Thyroid hormones can influence mood and cognitive function. Individuals with psychiatric disorders may require close monitoring and adjustment of medication dosages. 

Pregnancy / Lactation

Pregnancy consideration:   

Pregnancy category: N/A 

Lactation: excreted into human milk: unknown  

Pregnancy categories:  

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• 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: 

Dextrothyroxine, also known as D-thyroxine, is a synthetic thyroid hormone that serves as the dextrorotatory isomer of levothyroxine, the active form of the thyroid hormone thyroxine (T4). Like levothyroxine, dextrothyroxine functions by replacing or supplementing endogenous thyroid hormones in individuals with hypothyroidism.

It acts on thyroid hormone receptors to regulate metabolism, support energy balance, and contribute to various physiological processes. However, dextrothyroxine has diminished in clinical use over time, with levothyroxine being the preferred choice due to its stability and potency.

The pharmacology of dextrothyroxine involves its role as a synthetic thyroid hormone replacement, supporting normal thyroid function and metabolic processes in the body. It is essential to consider individual health conditions, potential interactions, and specific patient needs when prescribing or using dextrothyroxine.  

Pharmacodynamics: 

• Thyroid Hormone Receptor Binding: Dextrothyroxine binds to thyroid hormone receptors, particularly in the nucleus of target cells. The binding initiates a series of cellular responses that regulate gene expression. 
• Metabolic Effects: Thyroid hormones, including dextrothyroxine, play a crucial role in regulating metabolism. They influence the rate at which cells utilize energy, affecting processes such as carbohydrate, lipid, and protein metabolism. 
• Energy Balance: By influencing metabolism, dextrothyroxine helps maintain energy balance in the body. It supports conversion of nutrients into energy and contributes to overall metabolic homeostasis. 
• Thermogenesis: Thyroid hormones stimulate thermogenesis, the production of heat, by increasing the metabolic rate. This effect contributes to the regulation of body temperature.

Pharmacokinetics: 

• Absorption: Dextrothyroxine is typically administered orally, and absorption occurs in the gastrointestinal tract. Absorption can be influenced by food and other medications. Thyroid hormones, in general, are known to be absorbed more efficiently on an empty stomach, and certain substances, such as calcium supplements or iron, may interfere with absorption. 
• Distribution: Once absorbed, thyroid hormones are bound to plasma proteins, primarily thyroxine-binding globulin (TBG), albumin, and prealbumin. This binding influences the distribution of thyroid hormones in the bloodstream. Thyroid hormones can enter cells and tissues, and their distribution is crucial for their effects on metabolism and other physiological functions. 
• Metabolism: Thyroid hormones, including dextrothyroxine, undergo metabolic processes, primarily in the liver. Enzymes, such as deiodinases, play a role in converting thyroxine (T4) into the more active triiodothyronine (T3). The metabolism of thyroid hormones is essential for maintaining the balance between inactive and active forms. 
• Excretion: Excretion of thyroid hormones occurs primarily through the kidneys. Both free and conjugated forms of thyroid hormones are excreted in the urine. The elimination half-life of thyroid hormones can vary, and factors such as age and kidney function may influence the excretion process. 

Adminstartion

Administration: 

• Dosage: Dextrothyroxine is often available in oral tablet form. The dosage of dextrothyroxine is determined by the healthcare provider based on the individual’s thyroid function and specific medical needs. It is important to adhere to the prescribed dosage to maintain thyroid hormone levels within the therapeutic range. 
• Timing of Administration: Thyroid hormones are often recommended to be taken on an empty stomach, preferably in the morning, to maximize absorption. This is because certain substances, including food and other medications, can interfere with the absorption of thyroid hormones. 
• Individualized Treatment: The administration of dextrothyroxine is individualized based on the patient’s health status, response to the medication, and specific medical conditions. Healthcare providers consider factors such as age, weight, presence of comorbidities, and other medications the patient is taking. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: dextrothyroxine 

Pronounced: (dex-troh-thy-ROX-een)  

Why do we use dextrothyroxine? 

Dextrothyroxine, a synthetic thyroid hormone and the dextrorotatory isomer of levothyroxine, has historically been used for thyroid hormone replacement therapy in hypothyroidism. Its purpose is to supplement or replace endogenous thyroxine, supporting metabolic functions, energy balance, and overall well-being.

However, the use of dextrothyroxine has diminished over time, with levothyroxine being the more widely prescribed and preferred form of thyroid hormone replacement. Levothyroxine is favored due to its stability, potency, and predictable pharmacokinetics.