Levothyroxine sodium – Anhydrous vs. Pentahydrate

[helvella]

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:

dropbox.com/s/pqwuga75fxvkd...

[Morning_gl0ry]

Thank you so much for posting this info! Amazing and very interesting indeed. It never ceases to amaze me how more there is to know about this subject. Best wishes x

[helvella Administrator Thyroid UK in reply to Morning_gl0ry]

The question over why some makes put the word "anhydrous" in their Patient Information Leaflets when some don't has been asked several times. I tried to answer that and couldn't easily, in a few sentences, on the forum.

However much we think we know, there is much, much more to be known. The history alone is fairly incredible.

[Miffie]

Thank you for another very informative post helvella .