Pharm

Liothyronine

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Liothyronine, Cytomel, Triostat, Triiodothyronine Replacement, T3 Replacement, Liotrix

  • See Also
  1. Hypothyroidism
  2. Levothyroxine
  • Indications
  1. Not generally recommended (no proven benefit and associated risk)
    1. Levothyroxine alone is preferred instead
    2. Levothyroxine (T4) is converted in peripheral tissues to Liothyronine (T3)
  2. May be used as an adjunct to Levothyroxine in Hypothyroidism
    1. Consider in lethargy or memory deficits despite normal TSH
  • Mechanism
  1. See Thyroid Physiology
  • Medications
  1. Liothyronine (Cytomel): 5 mcg, 25 mcg and 50 mcg
  2. Levothyroxine AND Liothyronine (Liotrix) combined tabs (T4/T3): 12.5/3.1 mcg, 25/6.25 mcg, 50/12.5 mcg, 100/25 mcg, 150/37.5 mcg
    1. Rare indications, but if used typically started in adults at 12.5/3.1 or 25/6.25 and titrated every 2 weeks
  • Dosing
  • Adults
  1. Combined with Levothyroxine
  2. Start: 1:14 ratio of Liothyronine to Levothyroxine
    1. Example: 5 mcg Liothyronine to 75 mcg Levothyroxine
  3. Typical Dose Range: 12.5 to 25 mcg orally daily
  4. Elderly: Start at 5 mcg/day (and titrate at 5 mcg/kg increments every 1 to 2 weeks)
  5. Maximum: 100 ug orally daily
  • Adverse Effects
  1. Risk of Cardiovascular Risks when combined with Levothyroxine
  2. See Levothyroxine
  • Safety
  1. Pregnancy Category A
  2. Unknown safety in Lactation
  • Efficacy
  1. May improve neuropsychiatric symptoms
  2. Changes after replacing T3 and T4
    1. Improved mood and energy
    2. Decreased confusion, fear, and irritability
    3. No difference in TSH normalization
  3. Studies suggests no benefit
    1. Clyde (2003) JAMA 290:2952-8 [PubMed]
  • Resources
  1. Liothyronine
    1. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=51452b31-ff68-4e0c-b982-c15502ebf1d3
  • References
  1. (2017) Presc Lett 25(1): 4
  2. Bunevicius (1999) N Engl J Med 340:424 [PubMed]