If you read about levothyroxine, especially as a medicine, you will see mention of two forms: levothyroxine sodium (anhydrous) and levothyroxine sodium. Although the second form doesn’t make it clear, it could refer to the anhydrous form or a hydrated form. We have to try to interpret from context and any other information present.
There is a difference between levothyroxine sodium (anhydrous) and the most common hydrated form, levothyroxine sodium pentahydrate.
Five water molecules are attached to the levothyroxine sodium molecule in the pentahydrate; none in the anhydrous.
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