Liotrix

Liotrix is a 4:1 mixture of thyroxine (T4) and triiodothyronine (T3) made synthetically. It is used to replenish thyroid hormones in thyroid deficiency and hypothyroidism. The only brand of liotrix available in the U.S. is Thyrolar, manufactured by Forest Laboratories.

Liotrix
Combination of
ThyroxineThyroid hormone
TriiodothyronineThyroid hormone
Clinical data
Trade namesThyrolar
AHFS/Drugs.comMultum Consumer Information
Routes of
administration		Oral
ATC code
Legal status
Legal status
Identifiers
CAS Number
PubChem CID
DrugBank
ChemSpider
  • none
UNII
CompTox Dashboard (EPA)

In 2013, Forest Laboratories has released the following statement regarding the limited availability of liotrix: "U.S. Pharmacopeia, an official public standards-setting authority for prescription and over-the-counter medicines and other health care products manufactured or sold in the United States, has mandated new specifications for a component used in the manufacturing of Thyrolar. As a result, all strengths of Thyrolar are currently on long-term back order while modifications necessary to meet these new specifications are made."[1]

Indications

The most common usage is hypothyroidism treatment, via supplementation.[2][3] Other uses include:

Adverse effects

Adverse effects are mainly due to chronic accidental overdose. Symptoms mimic those of hyperthyroidism and include headache, chest pain, irregular heartbeat, dyspnea, trembling, sweating, diarrhea, and weight loss. These effects can be reduced through titration of the dose levels, but this should be done by the prescribing physician.[4] Sympathomimetic cardiovascular effects including: heart palpitations, chest pain, arrhythmia, sweating, chest pain, and anxiety, require urgent medical attention.[5] Particularly if these signs occur in patients who are at an increased risk for cardiovascular complications i.e. familial or patient history of myocardial infarction, cardiovascular disease, stroke, arteriosclerosis.[2] Hair loss occasionally occurs in the first few months of treatment, but is reversible. The condition is usually self-limiting without altering treatment.[5]

Contraindications

Thyroid agents should not be used to treat obesity, particularly in euthyroid patients. Regular doses in hypothyroid patients are acceptable, but only in the context of treating hypothyroidism. Excessive doses (and regular doses in euthyroid patients) can result in life-threatening cardiovascular events. Patients should be advised against taking sympathomimetic agents, including stimulants and diet pills, while undergoing hypothyroid treatment, as these agents increase the risk of cardiovascular events.[6]

References
  1. "Thyrolar". Forest Pharmaceuticals, Inc. Archived from the original on 11 August 2008.
  2. "Liotrix (Professional Patient Advice)".
  3. Skidmore-Roth L (2015). "Liotrix". Mosby's 2015 nursing drug reference (Twenty-eight ed.). Saint Louis, Missouri: Elsevier Health Sciences. p. 713. ISBN 978-0-323-28693-0.
  4. "LIOTRIX - ORAL (Thyrolar) side effects, medical uses, and drug interactions". MedicineNet.
  5. "Thyrolar (Liotrix) dosing, indications, interactions, adverse effects, and more". MedScape.
  6. "Thyrolar (Liotrix) dosing, indications, interactions, adverse effects, and more". MedScape.
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