helvella – Levothyroxine sodium – Anhydrous vs. Pentahydrate
If you read about levothyroxine, especially as a medicine, you will see mention of two forms used as the Active Pharmaceutical Ingredient (API) in levothyroxine medicines: levothyroxine sodium (anhydrous) and levothyroxine sodium. Although the second form doesn’t make it clear, it could refer either to the anhydrous form or to a hydrated form. We have to try to interpret from context and any other information present.
There is a genuine 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
The rest of this document includes formatting and images which I cannot include here. The document has just been updated - 6th March 2021 - to include some information I have recently found. Here is a link to a PDF: