Action and Spectrum

Actions and Spectrum: 

Actions: 

• liothyronine acts directly on the nucleus of cells, where it promotes the transcription of genes involved in metabolic processes. 
• It increases the rate of glucose, fat, and protein metabolism in the body, leading to an increase in energy production and heat generation. 
• It stimulates the activity of the cardiovascular system, including the heart and blood vessels, leading to an increase in heart rate, cardiac output, and blood pressure. 
• It enhances the action of other hormones, such as growth hormone, insulin, and glucocorticoids. 
• It promotes the growth and differentiation of cells in various tissues, including bone, muscle, and brain. 

Spectrum: 

• liothyronine is primarily used to treat hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormones. 
• It can also be used in the management of certain thyroid cancers and goiters (enlarged thyroid gland). 
• liothyronine may be used in combination with other thyroid hormones or medications to treat depression, bipolar disorder, and other mental health conditions. 

Drug Interaction

Adverse Reaction

Frequency defined 

1-10% 

Tachycardia  

Hypotension  

Myocardial infarction  

Cardiopulmonary arrest 

<1% 

Hypertension 

Twitching 

Phlebitis 

Angina 

Fever 

Congestive heart failure 

Black Box Warning

Black Box Warning 

While thyroid hormones can increase metabolic rate and promote weight loss in individuals with hypothyroidism, they are not effective for weight loss in euthyroid individuals within the normal range of thyroid hormone production. In fact, taking larger doses of thyroid hormones can be dangerous, causing serious or even life-threatening side effects such as heart palpitations, chest pain, and irregular heartbeat. 

Furthermore, combining thyroid hormones with other weight loss medications such as sympathomimetic amines (e.g., amphetamines) can lead to even more serious side effects, including cardiovascular problems and addiction. 

Therefore, it is important to avoid using thyroid hormones for weight loss unless it is specifically prescribed by a healthcare professional for the treatment of hypothyroidism. For weight loss, individuals should focus on making healthy lifestyle changes, such as increasing physical activity and following a balanced diet. 

Contraindication / Caution

Contraindication/Caution: 

liothyronine, like any medication, has some contraindications and cautions that should be considered before use. Here are some of the most important ones: 

• Hypersensitivity: liothyronine should not be used in patients with a known hypersensitivity to the drug or any of its components. 
• Acute myocardial infarction: liothyronine should not be used in patients with acute myocardial infarction (heart attack). 
• Hyperthyroidism: liothyronine should not be used in patients with hyperthyroidism (overactive thyroid gland). 
• Adrenal insufficiency: liothyronine should be used with caution in patients with adrenal insufficiency (a condition where the adrenal glands do not produce enough hormones). 
• Cardiovascular disease: liothyronine should be used with caution in patients with cardiovascular disease, such as hypertension, angina, or arrhythmia. 
• Pregnancy and breastfeeding: liothyronine should be used with caution during pregnancy and breastfeeding, as it can cross the placenta and be secreted into breast milk. 
• Interactions: liothyronine can interact with other medications, including blood thinners, diabetes medications, and antidepressants, so it’s important to inform your healthcare provider of all medications you are taking. 

Pregnancy / Lactation

Pregnancy consideration:  

Category A 

Breastfeeding warnings:  

liothyronine is distributed in breastmilk and hence use with caution if breastfeeding  

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: No evidence shown of risk to the fetus found in animal reproduction studies, and there are not enough studies on pregnant women    
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a product in humans; Pregnant women must take care of the potential risks. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits. The drug is not for pregnant women. 
• Category N: No data is available for the drug under this category. 

Pharmacology

Pharmacology: 

• Mechanism of action: liothyronine acts on the nucleus of cells to increase transcription of genes involved in metabolism, energy production, and protein synthesis. It also increases the activity of the sodium-potassium ATPase pump, which leads to increased oxygen consumption, heat production, and metabolic rate. 
• Therapeutic uses: liothyronine is mainly used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. It may also be used as a diagnostic tool to assess thyroid function in patients with suspected hyperthyroidism. 
• Adverse effects: liothyronine can cause adverse effects such as heart palpitations, chest pain, and irregular heartbeat, especially when taken in larger doses. It can also lead to hyperthyroidism and thyroid storm, a life-threatening condition characterized by fever, sweating, and rapid heart rate. 
• Drug interactions: liothyronine can interact with other medications, including blood thinners, diabetes medications, and antidepressants, so it’s important to inform your healthcare provider of all medications you are taking. 

Pharmacodynamics: 

• Stimulation of metabolism: liothyronine increases the basal metabolic rate of the body by stimulating the breakdown of carbohydrates, fats, and proteins. This results in an increase in energy expenditure, heat production, and oxygen consumption. 
• Cardiac effects: liothyronine increases the contractility and rate of the heart, resulting in an increase in cardiac output and blood flow to the tissues. 
• Growth and development: liothyronine are essential for normal growth and development, particularly in the brain and bones. 
• Lipid metabolism: liothyronine increases the breakdown of cholesterol and other lipids, leading to a decrease in serum lipid levels. 
• Protein metabolism: liothyronine stimulates the breakdown of protein in muscle tissue, leading to an increase in amino acid availability for energy production. 
• Thermoregulation: liothyronine increases heat production in the body, which helps to maintain a normal body temperature. 

Pharmacokinetics: 

liothyronine is administered orally or by injection and is 

Absorption 

95% is absorbed 

The time of onset of action is 2-4 hours 

Duration of action is several days (hypothyroidism) 

Peak plasma concentration is achieved in 1-2 hours 

Max response takes place in 2-3 days 

Distribution 

The protein bound is 99.7% 

Metabolism 

The drug is hepatically metabolized in to deiodinated and conjugated metabolites 

Elimination 

The half-life is 2.5 days 

The drug is excreted in Urine and feces 

Adminstartion

Administration: 

liothyronine is typically administered orally as a tablet or capsule and is usually taken once daily in the morning on an empty stomach, at least 30 minutes before breakfast. The dose of liothyronine is individualized and depends on the patient’s age, weight, and medical condition. 

It is important to follow the prescribed dosage and administration instructions provided by the healthcare provider, as well as any dietary restrictions or other instructions. liothyronine should not be taken with food or other medications, as this may affect its absorption and effectiveness. 

It is also important to monitor thyroid hormone levels regularly, as well as symptoms and side effects, to ensure that the dose is appropriate and to detect any potential complications. Changes in dosage or frequency of administration should only be made under the guidance of a healthcare provider. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: liothyronine 

Pronounced: Lio-thy-rin-one 

Why do we use liothyronine? 

liothyronine is used for various medical conditions, primarily those related to the thyroid gland and its function. It is commonly prescribed to treat hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormone. 

liothyronine is also used in the diagnosis and management of certain thyroid disorders, such as thyroid cancer and goiter. Additionally, it may be used in combination with other medications to treat depression, bipolar disorder, and other mental health conditions. 

liothyronine is also sometimes used off-label for weight loss and bodybuilding, as it can increase metabolic rate and energy expenditure. However, its use for these purposes is controversial and not recommended by healthcare providers, as it can lead to serious side effects and complications. 

It is important to note that liothyronine should only be used under the guidance of a healthcare provider and should not be used without a proper diagnosis and monitoring of thyroid hormone levels.