Description
Indications and Usage
Cytomel is indicated for:
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Primary or secondary hypothyroidism
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Congenital hypothyroidism
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Myxedema
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Goiter
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Thyroid suppression testing
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Adjunct therapy in certain types of thyroid cancer
Off-label uses include:
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Depression (as augmentation)
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Weight loss and fat burning (bodybuilding; not medically approved)
Dosage and Administration
Important: Dosage should always be individualized and prescribed by a healthcare provider.
General guidelines:
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Hypothyroidism:
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Initial: 5 mcg/day
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Maintenance: 25–75 mcg/day
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Dose adjustments every 1–2 weeks by 5–10 mcg increments
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Myxedema:
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Start low (e.g., 5 mcg/day), especially in elderly or cardiac patients
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Thyroid suppression testing:
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75–100 mcg/day for 7 days
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For bodybuilders (off-label/unapproved):
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Doses often range from 25–75 mcg/day, sometimes increasing to 100 mcg/day—but this carries significant risks (see side effects).
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Administration:
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Best taken once daily in the morning, on an empty stomach, 30 minutes to 1 hour before food.
Side Effects
Common side effects (usually from overdosage):
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Palpitations
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Nervousness
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Tremor
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Headache
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Insomnia
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Increased appetite
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Weight loss
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Sweating
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Heat intolerance
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Diarrhea
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Menstrual irregularities
Serious side effects:
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Cardiovascular: Arrhythmias, tachycardia, angina, heart failure (especially in elderly or heart disease patients)
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Endocrine: Suppression of TSH, adrenal insufficiency
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Psychiatric: Anxiety, irritability, mania (in predisposed individuals)
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Skeletal: Long-term use may cause bone loss (osteoporosis)
Note: T3 has a more rapid onset and shorter half-life than T4, so side effects may appear quickly and fluctuate with dose timing.
Pharmacokinetics
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Absorption: Nearly 95% orally bioavailable; rapid absorption in the small intestine
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Peak plasma levels: 2–4 hours after oral dose
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Onset of action: Within a few hours
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Half-life: ~1–2 days (shorter than T4, which is ~7 days)
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Protein binding: ~99% bound to serum proteins
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Metabolism: Mainly in the liver and kidneys by deiodination, conjugation
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Excretion: Via urine (mostly as inactive metabolites)
Contraindications
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Untreated thyrotoxicosis
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Acute myocardial infarction
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Uncorrected adrenal insufficiency
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Hypersensitivity to liothyronine
Drug Interactions
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Increased effect of: Anticoagulants, sympathomimetics
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Decreased effectiveness of T3: Iron, calcium, antacids, sucralfate, cholestyramine (take 4 hours apart)
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May affect levels of: Insulin, oral hypoglycemics, digitalis glycosides
Monitoring Parameters
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Serum TSH, free T3, free T4
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Heart rate, ECG (especially in elderly or cardiac patients)
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Weight and bone density with long-term use
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Signs of hyperthyroidism or hypothyroidism
Reviews
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