From the Research
The equivalent IV levothyroxine dose for 75 mcg of oral levothyroxine is approximately 50-60 mcg, considering the increased bioavailability of the IV formulation. When converting from oral to intravenous levothyroxine, a dose reduction of about 20-25% is recommended due to the increased bioavailability of the IV formulation, as it bypasses first-pass metabolism in the liver and variable gastrointestinal absorption 1. For a patient requiring conversion from oral to IV levothyroxine, the IV dose should be administered once daily, preferably at the same time each day for consistency. Some key points to consider when converting from oral to IV levothyroxine include:
- The IV dose may need adjustment based on the patient's clinical response and thyroid function tests 2
- Monitoring of thyroid function tests is essential when switching between formulations, as some patients may require individualized dosing 3
- If the patient is critically ill or unable to take oral medications for an extended period, the IV route provides an effective alternative to maintain appropriate thyroid hormone levels 4 It's also important to note that the actual dose may need adjustment based on the patient's clinical response and thyroid function tests, and some patients may require individualized dosing 5.