Liothyronine Sodium

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Cat Number

API0232091

CAS Number

55-06-1

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Product Detail Description Scientific Support Customer Q&A

CAS Number

55-06-1

EINECS

200-223-5

Storage

Store at room temperature

Synonyms

Triostat; Basoprocin; Ibiothyron; T3 sodium salt; Cynomel; L-Triiodothyronine sodium salt; Cytobin; Liothyronine sodium salt

Molecular Formula

C15H11I3NNaO4

Molecular Weight

672.95

Smiles

C1=CC(=C(C=C1OC2=C(C=C(C=C2I)C[C@@H](C(=O)[O-])N)I)I)O.[Na+]

Appearance

Light yellow to beige powder

Melting Point

205°C (dec.)

Boiling Point

563.5°C at 760 mmHg

Relative Density

2.4±0.1

General Description

Liothyronine sodium is the synthetic sodium salt of 3,5,3′‑triiodo‑L‑thyronine (T3), the physiologically active form of thyroid hormone. Compared to levothyroxine (T4), liothyronine has a much shorter half‑life (approximately 1‑2 days) and higher receptor binding affinity. The molecule contains three iodine atoms and is produced by deiodination of T4 in peripheral tissues.

Mechanism of Action

Liothyronine enters cells and binds to nuclear thyroid hormone receptors (TR‑alpha and TR‑beta), which heterodimerize with retinoid X receptors. This complex then binds to thyroid hormone response elements (TREs) on DNA, regulating the transcription of genes involved in metabolism, cardiac contractility, thermogenesis, and central nervous system development. T3 is approximately four times more potent than T4 on a weight basis due to its direct receptor activation.

Application

Liothyronine is indicated for the treatment of hypothyroidism, particularly in patients who cannot convert T4 to T3 adequately, and for the acute management of myxedema coma (with intravenous use). It is also used in thyroid suppression tests to differentiate between primary and secondary hypothyroidism. In contrast to levothyroxine, liothyronine produces rapid metabolic effects, making it useful when quick normalization of thyroid status is required.

In a prospective, randomized, double‑blind crossover trial, 75 hypothyroid patients received levothyroxine (LT4), LT4+liothyronine (LT3), or desiccated thyroid extract (DTE) for 22 weeks. No differences in thyroid symptom scores, quality of life, memory, or depression were seen in the whole group. However, among the one‑third of patients who were most symptomatic on LT4, treatment containing T3 (LT4+LT3 or DTE) significantly improved symptoms, quality of life, depression, and visual memory, and was strongly preferred. The authors conclude that while overall outcomes are similar, symptomatic patients benefit from T3‑containing regimens.

Fig. 1 Boxplots showing change scores from LT4 to the LT4/LT3 combination treatment, segmented by either low, medium, or high scores for those measures while on LT4. (Shakir MKM, et al., 2021)

References

Shakir MKM, et al. Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism. J Clin Endocrinol Metab. 2021;106(11):e4400-e4413.

Does Liothyronine Sodium require protection from light and oxygen during storage?

Yes, it is highly sensitive to light and air. Light causes photodegradation and oxygen causes oxidative deiodination. Store in light-resistant, airtight containers under inert gas.

What is the recommended storage temperature for Liothyronine Sodium?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which accelerates decomposition and loss of iodine content.

Is Liothyronine Sodium stable in tablet formulations with standard excipients?

Yes, when protected from light and moisture and packaged in blisters or light-resistant bottles.

How is the free iodide content and related iodothyronine impurities monitored?

Free iodide is measured by ion chromatography. Related impurities (e.g., triiodothyroacetic acid) are quantified using a stability-indicating HPLC method.