How important is it to have reasonably fresh Armour thyroxine?

[rosiebones]

I'm lucky enough to be on Armour thyroxine but as it is a natural as against synthetic form of medication does the use by date have more relevance? My current lot has 11/13 on it, seems a bit tight?

[susymac]

If its unopened it should be ok, but I have found a couple of times that it seems to lose potency the older it is. Ive taken it past its use by date before though... needs must and all that

Make sure you keep it air tight, and in a cool place to keep it longer.

[rosiebones]

Thank you susymac, sounds about right. I wonder how many others have noticed a drop off in potency under these circumstances?

[debjs]

My Armour never seems to have a very long use by date so have not noticed a reduction in potency but when I asked the pharmacist he said that potency does not decrease until it is past its use by date.

[helvella Administrator in reply to debjs]

I don't know how the Armour knows not to deteriorate before the expiry date!

My guess is that it should have a potency within the applicable range up to the expiry date - so long as it has been kept in decent storage conditions. But that allows a deterioration margin. For example, USA levothyroxine has to remain within 95 to 105% of claimed potency - not sure what the range is for desiccated thyroid.

Rod

[rosiebones in reply to helvella]

I realise you were joking however my question may not have been worded clearly. I was wondering whether anyone had noticed a drop off in potency in meds close to the use by date not noted in meds well within the date.

[helvella Administrator in reply to rosiebones]

Absolutely people have noticed.

I think that they have had to tighten the expiry dates for Armour to keep it within the allowed range.

Many people dose their desiccated thyroid (whichever make) at least partly on how they feel. So there is a tendency to slightly increase the dose if it has reduced potency. Medics are probably all too happy to use that as part of the argument about it being unstable and therefore not to be prescribed. A pity they don't read that exactly the same arguments apply to levothyroxine.

Rod

[rosiebones in reply to debjs]

Thank you debjs. I rang my pharmacist following your reply. He said that the unofficial use by date is months over the official one on the package. He said that although it is not licenced in the UK they are legally bound to give a reasonable margin of time. Yes storage is important as you said.