From the FDA Drug Label
The dosage of thyroid hormones is determined by the indication and must in every case be individualized according to patient response and laboratory findings. Mild Hypothyroidism Recommended starting dosage is 25 mcg daily. Daily dosage then may be increased by up to 25 mcg every 1 or 2 weeks. Usual maintenance dose is 25 to 75 mcg daily Myxedema Recommended starting dosage is 5 mcg daily This may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks until a satisfactory therapeutic response is attained. Usual maintenance dose is 50 to 100 mcg daily
The proper use of Cytomel (liothyronine) for treating hypothyroidism involves:
- Individualized dosage: determined by patient response and laboratory findings
- Mild hypothyroidism:
- Starting dosage: 25 mcg daily
- Maintenance dose: 25 to 75 mcg daily
- Myxedema:
- Starting dosage: 5 mcg daily
- Maintenance dose: 50 to 100 mcg daily
- Dosage adjustments: should be made every 1 or 2 weeks, with increases of 5 to 25 mcg daily 1
From the Research
Cytomel (liothyronine or T3) should be used as a second-line treatment for hypothyroidism, usually in combination with levothyroxine (T4), for patients who remain symptomatic on LT4 therapy, with a starting dose of 2.5-7.5 mcg once or twice a day, after reducing the LT4 dose by 25 mcg/day. This approach is supported by recent studies, including a 2020 study published in the Thyroid journal, which found that combination therapy with LT4+LT3 can restore euthyroidism while maintaining a normal serum TSH, without increased mortality or morbidity risk due to cardiovascular disease, atrial fibrillation, or fractures 2.
When using Cytomel, it is essential to monitor treatment with regular thyroid function tests, typically every 6-8 weeks during dose adjustments and then every 6-12 months once stable. The medication works more rapidly than levothyroxine because it's the active thyroid hormone that doesn't require conversion in the body, making it useful for patients who have difficulty converting T4 to T3. However, this also increases the risk of side effects like heart palpitations, anxiety, and insomnia.
Some key points to consider when using Cytomel include:
- Starting with a low dose and gradually increasing as needed
- Taking the medication consistently at the same times each day, preferably on an empty stomach
- Being aware that missed doses can quickly lead to symptom recurrence due to its short duration of action
- Regularly monitoring thyroid function tests to adjust the dose as needed
A more recent study published in 2023 in the Clinical Endocrinology journal provides further guidance on the use of liothyronine in hypothyroidism, emphasizing the importance of a shared decision between patient and clinician, and considering combination therapy with LT4+LT3 for patients with confirmed overt hypothyroidism and persistent symptoms who have had adequate treatment with levothyroxine 3.
It's also important to note that while some studies have investigated the use of Cytomel in hypothyroidism, the evidence is not always consistent, and some studies have found no benefit to combination therapy over levothyroxine monotherapy 4, 5. However, the most recent and highest-quality studies support the use of Cytomel as a second-line treatment for hypothyroidism, in combination with levothyroxine, for patients who remain symptomatic on LT4 therapy.