Liothyronine (T3)

Oral capsule (slow-release): Swallow intact with a full glass of water. Administer consistently at the same time each day, preferably on an empty stomach or at least 30–60 minutes before food to maximize absorption. Avoid co-administration within 4 hours of calcium supplements, antacids, iron, or bile acid sequestrants, which reduce absorption. Liothyronine has a rapid GI absorption — approximately 95% within 4 hours — producing measurable effects within a few hours and peak response within 2–3 days.

Dosing is highly individualized and must be determined by the prescribing clinician based on clinical response and laboratory parameters (free T3, TSH).

• Adults (general): Initial starting doses typically range from 5–25 mcg/day; titration proceeds in 5–25 mcg increments every 1–2 weeks.
• Elderly and cardiac patients: Begin at 5 mcg/day with slow upward titration in 5 mcg increments to minimize cardiovascular stress.
• Typical maintenance: 25–75 mcg once daily (FDA-approved range); compounded slow-release formulations may be split twice daily to reduce peak serum excursions.
• TSH suppression (thyroid cancer adjunct): Dose targeting is individualized to achieve the desired TSH nadir.
• Final dosing — including form, strength, and frequency — is determined solely by the prescriber.

• Liothyronine (T3): Diffuses into the cell nucleus and binds to thyroid hormone receptor proteins (THR-α and THR-β) attached to specific DNA response elements, forming a hormone-receptor complex that activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. This drives increased basal metabolic rate, oxygen consumption, cardiac output, carbohydrate and lipid metabolism, protein synthesis, and myelination of the nervous system. Approximately 80% of circulating T3 in a healthy individual derives from peripheral deiodination of T4; exogenous liothyronine bypasses this conversion step entirely.

Primary indications: Replacement therapy for primary, secondary, or tertiary hypothyroidism (including Hashimoto's thyroiditis); adjunct to surgery and radioiodine in well-differentiated thyroid cancer (TSH suppression); diagnostic thyroid suppression testing. Off-label adjunctive use in refractory depression has been studied.

Prescriber monitoring considerations:

• Baseline and periodic TSH, free T3, free T4; in primary hypothyroidism, TSH is the primary monitoring marker.
• Because liothyronine has a short half-life, TSH suppression is influenced more by T4 levels than T3; a total T3 measurement may better reflect acute adequacy than TSH alone.
• Monitor heart rate, blood pressure, and symptoms of hyperthyroidism (palpitations, tremor, heat intolerance, insomnia) at each dose adjustment.
• Bone mineral density assessment in postmenopausal women on long-term therapy — excess thyroid hormone increases bone resorption.
• Adjust antidiabetic agent or insulin doses as thyroid hormone increases metabolic clearance.
• Monitor INR closely when initiating or adjusting dose in patients on warfarin.

Contraindications:

• Uncorrected adrenal cortical insufficiency (thyroid hormone increases cortisol clearance, potentially precipitating adrenal crisis)
• Known hypersensitivity to any component of the formulation
• Not for use in obesity or for weight loss — serious, life-threatening toxicity can occur

Warnings & Precautions:

• Narrow therapeutic index — over- or under-treatment produces significant adverse effects on cardiac, bone, reproductive, and metabolic function
• Cardiovascular risk: tachycardia, arrhythmia, angina, and myocardial infarction may occur, especially in elderly patients or those with pre-existing coronary artery disease
• Myxedema coma: oral formulations are not appropriate — use IV thyroid hormone
• Pediatric overtreatment: craniosynostosis, premature epiphyseal closure, and accelerated bone age; undertreatment impairs neurocognitive development
• Pregnancy: dose requirements typically increase; monitor TSH every trimester

Drug Interactions:

• Bile acid sequestrants, calcium, iron, antacids: reduced T3 absorption — separate by ≥4 hours
• Warfarin: enhanced anticoagulant effect — monitor INR closely
• Sympathomimetics: risk of coronary insufficiency
• Ketamine: marked hypertension and tachycardia
• Tricyclic antidepressants: mutually potentiated effects and cardiac toxicity risk
• Rifampin, phenobarbital, phenytoin: increased T3 metabolism → may require dose increase
• Propranolol (>160 mg/day): decreases peripheral T4-to-T3 conversion

Common Side Effects: Symptoms of over-replacement include palpitations, tachycardia, nervousness, insomnia, tremor, weight loss, heat intolerance, diarrhea, excessive sweating, and headache.

Store compounded liothyronine capsules at controlled room temperature (20–25°C / 68–77°F), protected from light and moisture. Do not refrigerate or freeze. Keep tightly capped in the original dispensing container. The beyond-use date assigned by Genesis Compounding applies; do not use after that date. Discard any unused portion per applicable local regulations.

Is this the same as the brand-name Cytomel?

The active ingredient liothyronine is the same molecule, but this preparation is a prescriber-directed, patient-specific 503A compounded formulation — not FDA-approved as a compounded drug. The strength or release characteristics may differ from commercially available tablets based on the prescriber's clinical rationale.

Why might a prescriber choose compounded T3 instead of a commercial product?

Compounded liothyronine allows for customized strengths (e.g., very low starting doses for elderly patients), slow-release formulations to reduce peak-serum excursions, or combination with T4 in a single capsule — options not always available commercially.

How quickly will I notice a change in how I feel?

The onset of pharmacologic activity of liothyronine is within a few hours, with maximum effect in 2–3 days. However, clinical symptom improvement and TSH normalization may take several weeks depending on dose titration.

Can I take this with other medications or food?

Many drugs and dietary factors affect T3 absorption. Calcium, iron, antacids, and bile acid sequestrants should be separated by at least 4 hours. Warfarin, antidiabetic agents, and certain antidepressants require dose monitoring when thyroid therapy is initiated or changed. Always disclose all medications to your prescriber.

Is this medication FDA-approved?

Liothyronine sodium tablets are FDA-approved; however, this specific compounded preparation has not been evaluated or approved by the FDA for safety or efficacy. It is prepared by Genesis Compounding pursuant to a valid prescriber order for an identified patient under 503A pharmacy rules.