Liothyronine

Thyroid hormone, Hormone replacement

Liothyronine (T3, triiodothyronine sodium)

Cytomel (oral), Triostat (IV)

Experience

👥 No personal reports yet

⚕ No clinical reports yet

Log in to add your own experience.

Problems

No problems yet. Be the first to suggest one.

+ Add a problem

Titration strategies

No titration strategies yet. Be the first to suggest one.

+ Add a titration strategy

Effects

No effects listed yet. Be the first to suggest one.

+ Add an effect

Relevant anecdote

No anecdotes yet. Share a relevant one.

+ Add an anecdote

Relevant Literature

No literature entries yet.

Log in to submit relevant literature.

Pharmacy

Starting dose

Hypothyroidism: 5-25 mcg PO daily (start low, titrate slowly); myxedema coma: 5-20 mcg IV q4-12h with T4 loading

Preparations

5, 25, 50 mcg tablets (Cytomel); 10 mcg/mL IV (Triostat)

US FDA Max

100 mcg/d typical

Common uses

Classification(s)

Classes

Thyroid hormone, Hormone replacement

Pharmacology

Routes

Oral, IV

Onset

Hours (faster than T4); peak biologic activity 24-48 hours

Duration

24-72 hours

Half-life

~1 day (much shorter than T4's ~7 days)

Bioavailability

~95% (oral)

Pregnancy

T4 (levothyroxine) is the first-line in pregnancy; T3 is rarely needed.^{[citation needed]}

Legal status

Rx-only in US

Purported mechanism

Liothyronine is bioidentical T3 (triiodothyronine), the active thyroid hormone that binds nuclear thyroid hormone receptors with ~10× the affinity of T4; T4 (levothyroxine) is essentially a prodrug peripherally deiodinated to T3.▲0▼ Direct T3 supplementation bypasses peripheral deiodination, useful in myxedema coma (rapid clinical effect needed) and in some refractory hypothyroidism (combination T4+T3, controversial). Short half-life produces fluctuating serum levels with intermittent supraphysiologic peaks — one reason T4 monotherapy remains the practical standard.