l-Thyroxine [EPC]l-Triiodothyronine [EPC]Vitamin C [EPC]Non-Standardized Food Allergenic Extract [EPC]
Key Facts
According to the FDA-approved labeling (2024), Liothyronine is roughly 3 to 4 times more potent than levothyroxine (T4).
A 2023 study published in the Journal of Clinical Endocrinology & Metabolism suggests that T3/T4 combination therapy may improve quality of life for a subset of patients who remain symptomatic on T4 alone.
The American Thyroid Association (ATA, 2024) guidelines emphasize that Liothyronine should not be used as a primary treatment for obesity.
Data from the National Institutes of Health (NIH, 2024) indicates that Liothyronine reaches peak blood levels within 2 to 3 hours after oral administration.
According to the World Health Organization (WHO), thyroid hormones are essential for the neurological development of infants, but T4 is the preferred agent for congenital hypothyroidism.
The FDA (2024) maintains a Black Box Warning for Liothyronine regarding its misuse for weight loss in euthyroid individuals.
Clinical trials cited by DailyMed (2024) show that Liothyronine has an absorption rate of approximately 95% in the gastrointestinal tract.
The American College of Cardiology (2023) warns that Liothyronine must be used with extreme caution in patients with pre-existing coronary artery disease due to increased myocardial oxygen demand.
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Cytomel, you must consult a qualified healthcare professional.
Clinical Information
Detailed information about Cytomel
ℹ️Overview
Liothyronine is a synthetic form of the thyroid hormone triiodothyronine (T3) used to treat hypothyroidism and manage certain thyroid conditions. It belongs to the l-Triiodothyronine [EPC] drug class and is significantly more potent than levothyroxine (T4).
💊Usage & Dosage
Adult Dosage
The dosage of Liothyronine must be highly individualized based on the patient's age, the severity of the hypothyroidism, and the presence of underlying cardiovascular conditions. Healthcare providers typically follow a "start low and go slow" approach.
Mild Hypothyroidism: The usual starting dose is 25 mcg daily. The dosage may be increased by 12.5 to 25 mcg every 1 to 2 weeks until the desired clinical response is achieved. The standard maintenance dose is 25 mcg to 75 mcg daily.
Myxedema: The starting dose is usually 5 mcg daily. Because of the severity of the condition, increases are made cautiously, typically 5 to 10 mcg every 1 to 2 weeks. Maintenance doses range from 50 to 100 mcg daily.
Simple (Non-toxic) Goiter: The starting dose is 5 mcg daily, with increments of 5 to 10 mcg every week or two. The usual maintenance dose is 75 mcg daily.
TSH Suppression Test: Typically, 75 to 100 mcg is administered daily for 7 days, followed by a radioactive iodine uptake test.
Pediatric Dosage
Liothyronine is used in children, but extreme caution is required to ensure normal growth and development. Dosage is usually based on body weight and age.
Infants and Children: The recommended starting dose is 5 mcg daily. The dose is increased by 5 mcg increments every 3 to 4 days until the desired response is achieved.
Congenital Hypothyroidism: Rapid restoration of thyroid levels is critical to prevent permanent intellectual disability. However, levothyroxine (T4) is generally the preferred first-line agent for pediatric patients due to more stable blood levels.
Dosage Adjustments
Renal Impairment
Specific dosage adjustments for renal impairment are not typically defined in the manufacturer's labeling, as the drug is primarily metabolized by the liver. However, because thyroid hormones affect renal blood flow, patients with severe kidney disease should be monitored closely for changes in thyroid function tests.
Hepatic Impairment
Since the liver is a primary site for thyroid hormone metabolism and the production of binding proteins (like TBG), patients with significant liver disease may require more frequent monitoring of free T3 and TSH levels. Dose adjustments may be necessary if the liver's ability to process the hormone is compromised.
Elderly Patients
Patients over the age of 65 are more sensitive to the effects of Liothyronine, particularly the cardiovascular effects. The starting dose in the elderly is usually very low (5 mcg daily), and increments are made at longer intervals (3 to 4 weeks) to avoid precipitating heart failure or arrhythmias.
How to Take Liothyronine
Consistency is Key: Take Liothyronine at the same time every day to maintain steady hormone levels. Most patients take it in the morning.
Food Interactions: While Liothyronine is better absorbed with food than levothyroxine, it is still best to take it on an empty stomach (30-60 minutes before breakfast) to ensure the most consistent absorption.
Swallowing: Tablets should be swallowed whole with a full glass of water. If you have difficulty swallowing, discuss alternative formulations with your pharmacist.
Storage: Store at room temperature (68°F to 77°F or 20°C to 25°C) in a tight, light-resistant container. Keep away from excessive moisture.
Missed Dose
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not double the dose to catch up, as this can lead to symptoms of hyperthyroidism (overactive thyroid).
Overdose
An overdose of Liothyronine results in a hypermetabolic state (thyrotoxicosis). Symptoms include a rapid or irregular heartbeat, chest pain, extreme nervousness, confusion, seizures, and high body temperature. In the event of a suspected overdose, contact emergency services or a poison control center immediately. Treatment usually involves supportive care and medications like beta-blockers to control heart rate and blood pressure.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or switch brands without medical guidance, as different formulations may not be bioequivalent.
⚠️Side Effects
Common Side Effects (>1 in 10)
Side effects of Liothyronine are generally related to the dose being too high, effectively causing symptoms of hyperthyroidism (an overactive thyroid). Common side effects include:
Nervousness and Anxiety: Feeling "jittery," restless, or having difficulty sitting still.
Insomnia: Difficulty falling asleep or staying asleep due to increased metabolic stimulation.
Tachycardia: A rapid or racing heartbeat that you can feel in your chest (palpitations).
Heat Intolerance: Feeling excessively warm when others are comfortable, often accompanied by increased sweating.
Tremors: Small, involuntary shaking movements, most commonly in the hands.
🔴Warnings
Important Safety Information
Liothyronine is a potent medication that significantly alters the body's metabolic state. It should only be used under the strict supervision of a healthcare provider. Patients must be aware that thyroid replacement therapy is usually lifelong, and consistency in medication use and laboratory monitoring is essential for safety.
Black Box Warnings
Full Text Summary: The FDA has issued a Black Box Warning stating that Liothyronine must not be used for the treatment of obesity or weight loss. In individuals with normal thyroid function, standard doses are ineffective for weight loss, while high doses can cause severe, life-threatening toxicity, especially if combined with diet pills or stimulants.
Major Precautions
Cardiovascular Risk: Liothyronine increases heart rate and the force of heart contractions. It must be used with extreme caution in patients with cardiovascular disorders, such as coronary artery disease (angina), hypertension, or a history of heart attack. If chest pain or other cardiac symptoms develop, the dose must be reduced or withheld.
🔄Interactions
Contraindicated Combinations (Do Not Use Together)
There are few absolute contraindications for drug combinations, but the following require extreme caution:
Weight Loss Medications (Sympathomimetics): Combining Liothyronine with stimulants like phentermine or amphetamines for weight loss is strictly contraindicated due to the risk of fatal cardiac arrhythmias and severe hypertension.
Serious Interactions (Monitor Closely)
Oral Anticoagulants (e.g., Warfarin): Thyroid hormones increase the breakdown of clotting factors. This can significantly increase the blood-thinning effect of warfarin, increasing the risk of bleeding. Your doctor will need to monitor your INR (International Normalized Ratio) closely and likely reduce your warfarin dose when starting Liothyronine.
Insulin and Oral Antidiabetics: Liothyronine can decrease the effectiveness of insulin and oral diabetes medications (like metformin or glipizide). Blood sugar levels should be monitored more frequently, and diabetes medication doses may need adjustment.
🚫Contraindications
Absolute Contraindications
Liothyronine must NEVER be used in the following circumstances:
Untreated Thyrotoxicosis: If a patient already has an overactive thyroid (hyperthyroidism), adding synthetic T3 will dangerously exacerbate the condition, potentially leading to a thyroid storm (a life-threatening medical emergency).
Acute Myocardial Infarction (Heart Attack): Liothyronine increases the oxygen demand of the heart. Administering it during or immediately after a heart attack can worsen cardiac damage or trigger fatal arrhythmias.
Uncorrected Adrenal Insufficiency: Thyroid hormones increase the metabolic clearance of glucocorticoids. In patients with adrenal insufficiency, starting Liothyronine without first providing corticosteroid replacement can trigger an acute adrenal crisis (symptoms include severe low blood pressure, shock, and death).
Hypersensitivity: A known allergy to Liothyronine sodium or any of the inactive ingredients (such as corn starch or lactose) in the tablet formulation.
👥Special Populations
Pregnancy
FDA Pregnancy Category A: Thyroid hormones do not readily cross the placental barrier. Clinical experience has shown that Liothyronine is safe for use during pregnancy when used to maintain normal thyroid levels.
Importance of Treatment: Untreated hypothyroidism during pregnancy is associated with a higher risk of miscarriage, preeclampsia, and impaired neurological development in the fetus.
Monitoring: Thyroid requirements often increase during pregnancy. TSH levels should be monitored every 4-6 weeks during the first half of pregnancy and at least once in the third trimester.
T4 vs T3: Levothyroxine (T4) is generally the preferred treatment during pregnancy because T4 is the primary hormone that crosses the placenta to support fetal brain development. Liothyronine is usually only used if the mother cannot tolerate T4 or in specific combination therapies.
🧬Pharmacology
Mechanism of Action
Liothyronine (L-triiodothyronine) is the synthetic form of the most metabolically active thyroid hormone. Its primary mechanism involves entering the cell nucleus and binding to thyroid hormone receptors (TR-alpha and TR-beta). These receptors act as ligand-activated transcription factors. When Liothyronine binds, it causes the receptor to release co-repressors and recruit co-activators, which then initiates the transcription of messenger RNA (mRNA). This mRNA is translated into proteins that increase mitochondrial activity, stimulate the sodium-potassium ATPase pump, and enhance the expression of genes involved in energy production and metabolic rate.
Pharmacodynamics
Liothyronine has a rapid onset of action, with metabolic effects often beginning within a few hours of administration. Its duration of action is shorter than that of levothyroxine, lasting approximately 48 to 72 hours after the last dose. It does not require conversion by deiodinase enzymes, making its effect more direct and predictable in patients who may have impaired T4-to-T3 conversion. There is no evidence of tolerance development; the body's requirement for the hormone remains relatively stable unless the underlying disease state changes.
Pharmacokinetics
Frequently Asked Questions
Common questions about Cytomel
What is Liothyronine used for?
Liothyronine is primarily used as a replacement therapy for patients with hypothyroidism, a condition where the thyroid gland does not produce enough natural hormones. It is a synthetic version of the active T3 hormone, making it useful for patients who may not respond fully to levothyroxine (T4) alone. Additionally, it is used to treat or prevent goiters (enlarged thyroid glands) and as part of the management for thyroid cancer. In emergency settings, the intravenous form is the standard treatment for myxedema coma, a severe and life-threatening form of hypothyroidism. Because it is highly potent, it must be used carefully under medical supervision.
What are the most common side effects of Liothyronine?
The most common side effects of Liothyronine are essentially symptoms of an overactive thyroid, which occur if the dose is slightly higher than what the body needs. These include heart palpitations, a rapid heart rate, nervousness, tremors, and increased sweating. Many patients also report feeling excessively warm (heat intolerance) or having difficulty sleeping (insomnia). Some may experience headaches or temporary weight loss as their metabolism speeds up. If these symptoms are severe or persistent, it usually indicates that the dosage needs to be adjusted by a healthcare provider.
Can I drink alcohol while taking Liothyronine?
There is no known direct chemical interaction between Liothyronine and alcohol that would make the medication stop working. However, alcohol can mimic or worsen some of the side effects of thyroid medication, such as an increased heart rate, anxiety, or disrupted sleep patterns. For patients with underlying heart conditions, the combination of alcohol and T3 could potentially put extra stress on the cardiovascular system. It is generally recommended to consume alcohol only in moderation and to observe how your body reacts. Always consult your doctor if you have concerns about alcohol use and your specific thyroid condition.
Is Liothyronine safe during pregnancy?
Liothyronine is generally considered safe during pregnancy and is classified as FDA Pregnancy Category A, meaning studies have not shown a risk to the fetus. Maintaining normal thyroid levels is crucial for the health of both the mother and the developing baby, as untreated hypothyroidism can lead to complications like preeclampsia or developmental delays. However, levothyroxine (T4) is usually the preferred treatment during pregnancy because it more effectively crosses the placenta to support the baby's brain growth. If you are taking Liothyronine and become pregnant, your doctor will likely monitor your TSH levels very closely and may adjust your medication plan. Never stop taking your thyroid medication during pregnancy without consulting your obstetrician or endocrinologist.
How long does it take for Liothyronine to work?
Liothyronine works much faster than levothyroxine (T4) because it is already in the active T3 form and does not need to be converted by the body. Most patients will begin to see an increase in their metabolic markers within a few hours of the first dose. However, it may take several days or even a few weeks for you to feel a significant improvement in symptoms like fatigue or brain fog. Your doctor will typically wait 1 to 2 weeks before checking your blood levels to see if the dose is correct. Because the body takes time to adjust to new hormone levels, patience is necessary during the initial titration phase.
Can I stop taking Liothyronine suddenly?
You should never stop taking Liothyronine suddenly unless your doctor specifically instructs you to do so, such as in the case of a severe allergic reaction or cardiac emergency. Because Liothyronine provides an essential hormone that your body is not making enough of, stopping it will cause your hypothyroid symptoms to return, often quite rapidly. This can lead to extreme fatigue, depression, weight gain, and in severe cases, it could contribute to a dangerous condition called myxedema. If you need to stop the medication, your doctor will usually taper your dose or transition you to another form of thyroid replacement therapy. Always maintain an adequate supply of your medication to avoid running out.
What should I do if I miss a dose of Liothyronine?
If you miss a dose of Liothyronine, you should take it as soon as you remember that same day. However, if it is already close to the time for your next scheduled dose, skip the missed dose entirely and just take your next dose at the regular time. Do not take two doses at once to make up for the one you missed, as the high potency of T3 can cause temporary symptoms of hyperthyroidism like a racing heart or anxiety. Consistency is very important for thyroid health, so try to take your medication at the same time every morning. If you find yourself frequently forgetting doses, consider using a pill organizer or a phone alarm.
Does Liothyronine cause weight gain?
Liothyronine is generally associated with weight loss rather than weight gain because it increases the body's basal metabolic rate. When used correctly to treat hypothyroidism, it helps the body burn energy more efficiently, which often leads to the loss of excess weight gained during the hypothyroid state. However, if a patient is under-replaced (the dose is too low), they may continue to experience weight gain or difficulty losing weight. It is important to note that the FDA has a Black Box Warning against using Liothyronine specifically for weight loss in people with normal thyroid function, as this is dangerous and ineffective. If you experience unexpected weight gain while taking Liothyronine, you should have your TSH and T3 levels checked.
Can Liothyronine be taken with other medications?
Liothyronine can interact with many other medications, so it is vital to keep your doctor informed of everything you take. Common interactions include blood thinners like warfarin, which can become more powerful, and diabetes medications, which may become less effective. Supplements containing calcium, iron, or aluminum (like antacids) can block the absorption of Liothyronine if taken at the same time. To avoid this, you should generally wait at least four hours between taking your thyroid hormone and these types of supplements. Always provide a full list of your prescriptions, over-the-counter drugs, and herbal supplements to your pharmacist to check for safety.
Is Liothyronine available as a generic?
Yes, Liothyronine sodium is widely available as a generic medication, which is typically more cost-effective than the brand-name version, Cytomel. Generic versions are required by the FDA to be bioequivalent to the brand-name drug, meaning they must deliver the same amount of active ingredient into the bloodstream. However, some endocrinologists prefer that patients stay on the same manufacturer's version (whether brand or generic) once they are stabilized, as small variations in the inactive fillers could potentially affect absorption. If your pharmacy changes the manufacturer of your generic Liothyronine, you should monitor your symptoms and potentially have your blood levels re-checked after 6-8 weeks.
Similar Medications
Other drugs with the same active ingredient (Liothyronine)
Weight Loss: Unintended weight loss despite a normal or increased appetite.
Diarrhea: Increased frequency of bowel movements or loose stools due to accelerated gastrointestinal motility.
Headache: Persistent or tension-type headaches.
Menstrual Irregularities: Changes in the timing or flow of menstrual periods in women.
Muscle Weakness: A feeling of fatigue or lack of strength in the muscles, particularly the thighs and upper arms.
Rare Side Effects (less than 1 in 100)
Hair Loss: Temporary hair thinning may occur during the first few months of therapy, particularly in children (this usually resolves as the body adjusts).
Allergic Reactions: Rash, hives, or itching. These are rare as the drug mimics a natural hormone, but can occur due to inactive ingredients in the tablet.
Pseudotumor Cerebri: Increased pressure inside the skull, which can cause vision changes and severe headaches (primarily reported in children).
Serious Side Effects — Seek Immediate Medical Attention
> Warning: Stop taking Liothyronine and call your doctor immediately if you experience any of the following symptoms. These may indicate a life-threatening cardiovascular event or severe thyrotoxicosis.
Chest Pain (Angina): Pressure, tightness, or pain in the chest, which may spread to the arms, neck, or jaw.
Shortness of Breath: Difficulty breathing, especially when lying down or during mild exertion.
Severe Palpitations: A feeling that the heart is skipping beats or beating dangerously fast (arrhythmia).
Swelling (Edema): New or worsening swelling in the ankles, feet, or legs.
Fainting or Syncope: Sudden loss of consciousness or feeling like you are about to pass out.
Seizures: Involuntary muscle contractions or loss of awareness.
Long-Term Side Effects
Bone Mineral Density Loss: Chronic over-replacement with thyroid hormones can lead to increased bone resorption, potentially resulting in osteoporosis and an increased risk of bone fractures.
Cardiac Hypertrophy: Long-term exposure to high levels of T3 can cause the heart muscle to thicken, increasing the risk of heart failure over time.
Atrial Fibrillation: Especially in elderly patients, long-term use of slightly high doses can trigger chronic heart rhythm disturbances.
Black Box Warnings
FDA BLACK BOX WARNING: NOT FOR TREATMENT OF OBESITY OR WEIGHT LOSS
Thyroid hormones, including Liothyronine, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients (patients with normal thyroid function), doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic (appetite suppressant) effects. Using Liothyronine specifically for weight loss is dangerous and medically inappropriate.
Report any unusual symptoms or persistent side effects to your healthcare provider. Regular blood tests (TSH and T3 levels) are the best way to ensure your dose is correct and to minimize side effects.
Adrenal Insufficiency: In patients with concomitant (co-existing) adrenal insufficiency, thyroid hormone therapy must not be started until the adrenal condition is treated with glucocorticoids. Starting thyroid hormone first can precipitate an acute adrenal crisis, which is a medical emergency.
Diabetes Mellitus: Liothyronine can increase blood sugar levels. Patients with diabetes may require an increase in their insulin or oral glucose-lowering medications when starting or changing the dose of Liothyronine.
Myxedema Coma: While IV Liothyronine is used for this condition, it must be administered with caution as it can cause rapid shifts in fluid and electrolytes, potentially stressing the heart.
Bone Density: Excessive doses can lead to bone thinning (osteoporosis). Postmenopausal women and those at risk for bone loss should have their TSH levels monitored closely to ensure they are not being over-replaced.
Monitoring Requirements
To ensure the safety and efficacy of Liothyronine, your doctor will order regular blood tests:
TSH (Thyroid Stimulating Hormone): The primary marker used to determine if the dose is correct. High TSH usually means the dose is too low; low TSH usually means the dose is too high.
Free T3 (Triiodothyronine): Directly measures the amount of active hormone in the blood. This is particularly important for Liothyronine therapy.
Clinical Evaluation: Regular checks of heart rate, blood pressure, and body weight.
Bone Density Scans: May be recommended for patients on long-term therapy who are at risk for osteoporosis.
Driving and Operating Machinery
Liothyronine generally does not affect the ability to drive or operate machinery. However, if you experience side effects such as tremors, nervousness, or vision changes (rare), you should avoid these activities until the symptoms resolve.
Alcohol Use
There is no direct interaction between alcohol and Liothyronine. However, alcohol can worsen certain side effects like rapid heart rate or sleep disturbances. It is best to consume alcohol only in moderation while on thyroid therapy.
Discontinuation
Do not stop taking Liothyronine abruptly unless directed by your doctor. Sudden discontinuation will lead to a return of hypothyroid symptoms, which can be severe. If the medication needs to be stopped due to side effects, your doctor will provide a plan to transition to another therapy or manage the withdrawal of the hormone.
> Important: Discuss all your medical conditions, especially heart disease or adrenal problems, with your healthcare provider before starting Liothyronine.
Digitalis Glycosides (e.g., Digoxin): Thyroid hormones can decrease the effectiveness of digitalis. As thyroid status changes from hypothyroid to euthyroid, the dose of digoxin may need to be increased to maintain its effect on the heart.
Moderate Interactions
Bile Acid Sequestrants (e.g., Cholestyramine, Colestipol): These drugs bind to Liothyronine in the gut and prevent its absorption. Liothyronine should be taken at least 4 hours apart from these medications.
Antacids and Calcium Supplements: Aluminum-containing antacids, calcium carbonate, and iron supplements can interfere with the absorption of thyroid hormones. Space these at least 4 hours away from your Liothyronine dose.
Estrogens and Oral Contraceptives: Estrogens increase the level of thyroid-binding globulin (TBG) in the blood. This may decrease the amount of "free" (active) T3 available, potentially requiring an increase in the Liothyronine dose.
Tricyclic Antidepressants: Use with thyroid hormones may increase the activity of both drugs, potentially leading to heart rhythm issues or increased toxicity.
Food Interactions
Soy and Fiber: High-fiber diets or large amounts of soy can slightly decrease the absorption of thyroid hormones. While this is more significant for levothyroxine (T4), maintaining a consistent diet is important for stable T3 levels.
Grapefruit Juice: Unlike many other drugs, grapefruit juice does not have a major known effect on Liothyronine metabolism, but consistency in intake is always advised.
Herbal/Supplement Interactions
Kelp and Iodine Supplements: Since iodine is a component of thyroid hormone, taking extra iodine can interfere with thyroid function and the effectiveness of Liothyronine. Avoid high-dose iodine supplements unless directed by a doctor.
St. John's Wort: May potentially alter the metabolism of various drugs, though its specific effect on Liothyronine is not well-documented. Monitor for changes in symptoms.
Lab Test Interactions
Biotin (Vitamin B7): High doses of biotin (found in hair/skin/nail supplements) can interfere with thyroid lab tests, often causing falsely high T3 levels and falsely low TSH levels. Stop taking biotin at least 2 days before having thyroid blood work done.
For each interaction, the primary management strategy is frequent monitoring of TSH and T3 levels and adjusting the Liothyronine dose as necessary to maintain a euthyroid state.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, as many common items can interfere with thyroid hormone levels.
Relative Contraindications
These conditions require a careful risk-benefit analysis and very close medical supervision:
Severe Coronary Artery Disease: The risk of precipitating angina or a heart attack may outweigh the benefits of rapid T3 replacement. In these patients, levothyroxine (T4) is often preferred due to its slower onset.
Marked Hypertension: Because T3 can increase blood pressure and heart rate, it may complicate the management of severe high blood pressure.
Elderly Patients with Cardiac Comorbidities: The high potency and rapid action of T3 make it difficult to manage safely in frail elderly patients with multiple heart issues.
Cross-Sensitivity
There is no known cross-sensitivity between Liothyronine and unrelated drug classes. However, patients who have had a reaction to one brand of thyroid hormone should be cautious when switching to another, as the inactive fillers and dyes may differ.
> Important: Your healthcare provider will evaluate your complete medical history, especially your heart and adrenal health, before prescribing Liothyronine to ensure it is safe for you.
Breastfeeding
Passage into Milk: Small amounts of thyroid hormones are excreted into breast milk. However, these amounts are generally insufficient to affect the nursing infant or interfere with infant thyroid screening.
Safety: Liothyronine is considered compatible with breastfeeding. No special precautions are typically required, but mothers should continue their prescribed dose to remain euthyroid, which supports healthy lactation.
Pediatric Use
Growth and Development: Thyroid hormone is essential for bone maturation and brain development. Inadequate treatment can lead to permanent cognitive impairment and short stature.
Monitoring: Children require more frequent monitoring of TSH and T3 levels, as well as regular assessments of height and weight to ensure normal growth.
Side Effects: Children may be more prone to temporary hair loss and a rare condition called pseudotumor cerebri (increased brain pressure).
Geriatric Use
Cardiac Sensitivity: Patients over 65 are at a much higher risk for T3-induced cardiac issues, including atrial fibrillation and angina.
Dosing: The rule for the elderly is "Start Low and Go Slow." Doses often start at 5 mcg and are increased very gradually.
Polypharmacy: Elderly patients are more likely to be taking other medications (like beta-blockers or blood thinners) that interact with Liothyronine.
Renal Impairment
Adjustments: No specific dose adjustments are required for patients with kidney disease. However, since thyroid status affects kidney function (GFR), patients with chronic kidney disease should have their thyroid levels monitored closely as their renal function changes.
Hepatic Impairment
Metabolism: In patients with severe liver cirrhosis, the production of thyroid-binding proteins may be decreased, and the metabolism of the hormone may be slowed. This can lead to higher levels of "free" (active) T3, requiring a lower dose of Liothyronine.
> Important: Special populations require individualized medical assessment. Never share your medication with others, especially children or the elderly.
| Parameter | Value |
|---|---|
| Bioavailability | ~95% |
| Protein Binding | >99% (primarily TBG and Albumin) |
| Half-life | 1 - 2 days (shorter in hyperthyroidism) |
Solubility: Slightly soluble in water; soluble in alkaline solutions.
Structure: It is the sodium salt of the L-isomer of 3,3',5-triiodothyronine. It contains three iodine atoms per molecule, which are critical for its biological activity.
Drug Class
Liothyronine is classified as a synthetic thyroid hormone. Within the therapeutic area of endocrinology, it is categorized as an l-Triiodothyronine [EPC]. It is related to levothyroxine (T4) and desiccated thyroid extract (which contains both T3 and T4), but it is unique in providing only the pure, active T3 hormone.