There have been many discussions about the differences and availabilities of the two differently-labelled Mercury Pharma products. I recently contacted Advanz Pharma (who own the Mercury Pharma brand) and recieved a reply. I'm posting this as clarification:
Thank you for contacting ADVANZ PHARMA requesting clarification regarding Eltroxin branded and Mercury Pharma branded Levothyroxine marketed in the UK by ADVANZ PHARMA.
As you are aware the products below share the same product license (PL) number, therefore are of the same specification/formulation:
Eltroxin 25mcg tablets (PL 12762/0016)
Levothyroxine 25mcg tablets (PL 12762/0016)
Eltroxin 50mcg tablets (PL 10972/0031)
Levothyroxine 50mcg tablets (PL 10972/0031)
Eltroxin 100mcg tablets (PL 10972/0032)
Levothyroxine 100mcg tablets (PL 10972/0032)
The relevant department have also confirmed that both of the aforementioned products are available.
The generic Levothyroxine tablets are available as a bulk pack and 28 pack size whilst the Eltroxin brand is available only in a 28 pack size.
I hope this makes things clear. Though it is still difficult to properly understand why they continue with two liveries (labelling/packaging) for the same product!