From the FDA Drug Label
The recommended starting daily dosage of levothyroxine sodium tablets in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1 For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. Full replacement dose is 1.6 mcg/kg/day. Some patients require a lower starting dose. Titrate dosage by 12.5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid.
The recommended starting dose of Synthroid (levothyroxine) for a patient with subclinical hypothyroidism, a Thyroid-Stimulating Hormone (TSH) level of 9 and a normal Free Thyroxine (FT4) level is 1.6 mcg/kg/day for a full replacement dose, but some patients may require a lower starting dose. The dosage should be titrated by 12.5 to 25 mcg increments every 4 to 6 weeks until the patient is euthyroid, with consideration of the patient's age and comorbid cardiac conditions 1.
From the Research
For a patient with subclinical hypothyroidism, a TSH level of 9, and normal FT4, the recommended starting dose of Synthroid (levothyroxine) is typically 25-50 mcg once daily. This recommendation is based on the most recent and highest quality study available, which suggests that treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L 2.
Key Considerations
- The patient's TSH level is 9, which is slightly elevated but not significantly high enough to warrant aggressive treatment.
- The normal FT4 level indicates that the patient is not experiencing overt hypothyroidism.
- The goal of treatment is to normalize TSH levels, typically to a range of 0.5-4.5 mIU/L.
- Dose adjustments should be made in small increments (12.5-25 mcg) until the target TSH is achieved.
Administration and Monitoring
- The medication should be taken on an empty stomach, 30-60 minutes before breakfast, with a full glass of water for optimal absorption.
- After initiating therapy, TSH levels should be rechecked in 6-8 weeks to assess response and adjust dosing as needed.
- Starting with a lower dose helps minimize the risk of overtreatment, which could lead to symptoms of hyperthyroidism such as palpitations, anxiety, or insomnia.
Special Considerations
- This cautious approach is particularly important in elderly patients or those with cardiovascular disease, as they may be more susceptible to the adverse effects of levothyroxine 3.
- The patient's response to treatment should be closely monitored, and adjustments made as needed to ensure optimal outcomes and minimize potential risks.