Does anyone know exactly what the difference is? I've googled it but can't find anything. Do they both work in the same way?
Are they identical?
Is one more effective than the other?
Yours hopefully!
Xxx
WHAT IS THE DIFFERENCE BETWEEN Levothyroxine So... - Thyroid UK
WHAT IS THE DIFFERENCE BETWEEN Levothyroxine Sodium AND Levothyroxine Sodium Anhydrous?
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helvellaAdministratorThyroid UK
Pretty much nothing!
The word "anhydrous" means without water.
If you took a teaspoon of anhydrous levothyroxine sodium and put it on a saucer, then in a fairly short time (hours or days) it would grab some water from the air and turn into levothyroxine sodium pentahydrate. That is, each molecule of levothyroxine sodium would have five molecules of water attached to it rather than none.
The amount of levothyroxine sodium in a tablet is measured/calculated as if it is anhydrous. So a 100 mcg tablet has 100 mcg of anhydrous levothyroxine in it.
If they used levothyroxine pentahydrate, they would have to allow for it being a bit heavier!
But the manufacturing of tablets might itself affect the amount of water in there. Whatever they use as an ingredient, it might have a different amount of water in the final tablet.
There is a bit about different levels of hydration and stability in the recent MHRA report available here:
mhra.gov.uk/home/groups/pl-...
[Some time back, they found the potency of the original Kappin liquid levothyroxine was slightly low. I have always suspected they added the pentahydrate form but calculated as for the anhydrous form.]
Rod
[If I have confused, let me know, and my apologies. It is not easy to say it all in a modest number of words.]
Sodium L-thyroxine pentahydrate
Also known as: L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, sodium salt, pentahydrate
Molecular Weight: 888.928249 [g/mol]
Molecular Formula: C15H20I4NNaO9
Anhydrous Thyroxine
Also known as: Levothyroxine sodium, Unithroid, levothroid, Euthyrox, Levoxyl, Novothyrox, Sodium thyroxinate, L-Thyroxine sodium, Sodium L-thyroxine
Molecular Formula: C15H10I4NNaO4
Molecular Weight: 798.851849
You can see that the two molecular formulas differ by ten Hydrogen atoms and five Oxygen atoms - which is five lots of H2O - water!
I've just today been looking up the same thing,,, and this is the best explanation i can find,,,
I've gone onto mercury pharma from eltroxin and the merc one has anhydrous Levo but the eltroxin has just Levo ,, both sodium of course. I'm hoping this makes no difference to potency etc. thanks rod...
Hi,
I recently was informed regarding anhydrous and was told to check whether my tablet has it or not cos it's not a good thing...came across your response and honestly am a bit confused. If don't mind explaining whether it is a good thing or not?
And also in case know whether there is a more natural levothyroxine or we're just stuck with the ones provided?
Thanks
It is my view that it doesn't mean anything.
When you weigh out the levothyroxine powder in the factory, you absolutely MUST know whether it is anhydrous or not (and if not, exactly how much water it contains). I suspect that the manufacturers would always use anhydrous levothyroxine because any other choice would probably be more difficult to manage.
But by the time the tablets are in your hand, the level of hydration will be whatever it is after the manufacturing process and interaction with humidity in the atmosphere. Levothyroxine is renowned for both absorbing and releasing water if at all open to the atmosphere.
Some manufacturers also say that it is OK to disperse your tablets in water before swallowing. After doing that, I doubt whether much would remain anhydrous! 
In order to avoid confusion, I think that product documentation (Patient Information Leaflets and Summaries of Product Characteristics) now must state anhydrous levothyroxine sodium.
(A few years ago there was a situation in which it looked as if the manufacturer of a levothyroxine product actually did NOT base their calculations on the anhydrous form, and so ended up with a slightly sub-potent product.)
Oh so then why are there tablets with anhydrous and without and someone told me that it is not good if the tablet has anhydrous??? as if it wasn't bad enough to deal with UAT and now tablets too.... Sometimes I just can't take it.....
Please bear in mind that if someone writes "levothyroxine sodium" as an ingredient, that would include "levothyroxine sodium anhydrous".
The Mercury Pharma products state:
Each strength contains respectively 50 and 100 micrograms of anhydrous levothyroxine sodium.
But that does NOT say anything about how hydrated or anhydrous the substance was when delivered to the factory or put into the mixer. It says that if you could extract all the levothyroxine and remove all the water - there would be 50 or 100 micrograms of levothyroxine. It is done like this so that even if tablets absorb or lose water, the precise amount of levothyroxine is known and can be checked.
Both Actavis and Mercury Pharma say "levothyroxine sodium anhydrous". The only other UK make, Wockhardt, says:
Each tablet contains 27.8 micrograms of levothyroxine sodium equivalent to 25 micrograms of anhydrous levothyroxine sodium.
It is mandatory to assess the product on the basis of anhydrous levothyroxine.
I'd also be interested to know on what basis "someone told you". There are all too many rumours in the thyroid world as elsewhere. Some are substantiated over time, but many are shown to be false or misleading.
that's the reason I always double check and try and find out more info before deciding whether or not it's accurate or as you said rumours etc...
I was trying to find UK brands or manufacturers in case you know is almus and actavis the same or separate? couldn't find solid info regarding that....
Would you by any chance know whether there'd be any difference in the tablet amongst these different manufacturers in the country like actavis, mercury, wockhardt, eltroxin, teva aliud pharma etc?
Almus is simply Actavis packaged for distribution by Boots.
Teva levothyroxine lost its licence a few years ago because it was sub-potent.
In UK terms, look at the product licence number. If it is the same, then it is the same product.
In the UK we currently have only three makes - Mercury Pharma, Actavis and Wockhardt.
You will find quite a lot of information on the main Thyroid UK site:
thyroiduk.org.uk/tuk/treatm...
And many (sadly, not all) UK medicines are documented here:
You keep referring to the UK as if you are elsewhere. It helps people answering your questions/posts if you state on your profile which country you live in.
helvellaAdministratorThyroid UK
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This thread also contains some out of date information.
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