A few days ago there was some uncertainty about the potency requirement for liothyronine in the UK. Because I did not know, I asked the MHRA who have responded:
•British Pharmacopoeia Volume III
•Formulated Preparations: Specific Monographs
Action and use
Thyroid hormone replacement.
Liothyronine Tablets contain Liothyronine Sodium.
The tablets comply with the requirements stated under Tablets and with the following requirements.
Content of liothyronine sodium, C15H11I3NNaO4
90.0 to 110.0% of the stated amount.
Have to say, I think that is a big range. Though it was only a few years ago that the standard for levothyroxine was tightened from this same range to 90 to 105%. (95 to 105% in the USA.)
Also bear in mind that Mercury Pharma seem to have repeated difficulty in manufacturing to the existing standards - what would they do if they were tightened up? (Mind, we don't actually know that the problem is with potency, it could be other issues.)