Levothyroxine sodium revisited: A wholistic structural elucidation approach of new impurities

All levothyroxines are equal, but some are more equal than others... :-(

At last, a bit more evidence as to why the various levothyroxine products might vary in impact. With 24 novel compounds, it is impossible to know their impact on our bodies. There cannot have been investigation of them if no-one knew what they are!

Although we regularly see claims about the excipients being the cause of issues, I have long wondered about impurities. For example, perhaps, for some, it isn't the lactose itself, that is the issue (even if somewhat lactose intolerant) but some compound formed by reaction between levothyroxine and lactose?

Sadly, the full paper is behind a paywall and, even if we gained access, I doubt we would see manufacturers' names.

J Pharm Biomed Anal. 2016 Dec 14;135:140-152. doi: 10.1016/j.jpba.2016.12.002. [Epub ahead of print]

Levothyroxine sodium revisited: A wholistic structural elucidation approach of new impurities via HPLC-HRMS/MS, on-line H/D exchange, NMR spectroscopy and chemical synthesis.

Ruggenthaler M1, Grass J2, Schuh W2, Huber CG3, Reischl RJ4.

Author information

1SANDOZ GmbH, Biochemiestraße 10, A-6250 Kundl/Tirol, Austria; Department of Molecular Biology, Division of Chemistry and Bioanalytics,University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria.

2SANDOZ GmbH, Biochemiestraße 10, A-6250 Kundl/Tirol, Austria.

3Department of Molecular Biology, Division of Chemistry and Bioanalytics,University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria.

4Department of Molecular Biology, Division of Chemistry and Bioanalytics,University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria. Electronic address: roland.reischl@sbg.ac.at.

Abstract

The structural elucidation of unknown pharmaceutical impurities plays an important role in the quality control of newly developed and well-established active pharmaceutical ingredients (APIs). The United States Pharmacopeia (USP) monograph for the API Levothyroxine Sodium, a synthetic thyroid hormone, features two high pressure liquid chromatography (HPLC) methods using UV-VIS absorption detection to determine organic impurities in the drug substance. The impurity profile of the first USP method ("Procedure 1") has already been extensively studied, however for the second method ("Procedure 2"), which exhibits a significantly different impurity profile, no wholistic structural elucidation of impurities has been performed yet. Applying minor modifications to the chromatographic parameters of USP "Procedure 2" and using various comprehensive structural elucidation methods such as high resolution tandem mass spectrometry with on-line hydrogen-deuterium (H/D) exchange or two-dimensional nuclear magnetic resonance spectroscopy (NMR) we gained new insights about the complex impurity profile of the synthetic thyroid hormone. This resulted in the characterization of 24 compounds previously unknown to literature and the introduction of two new classes of Levothyroxine Sodium impurities. Five novel compounds were unambiguously identified via isolation or synthesis of reference substances and subsequent NMR spectroscopic investigation. Additionally, Collision-Induced Dissociation (CID)-type fragmentation of identified major impurities as well as neutral loss fragmentation patterns of many characterized impurities were discussed.

Copyright © 2016 Elsevier B.V. All rights reserved.

KEYWORDS:

HDX; LC-MS; Levothyroxine; On-line H/D Exchange; Pharmaceutical impurities; Thyroid hormone

PMID: 28024262

DOI: 10.1016/j.jpba.2016.12.002

[PubMed - as supplied by publisher]

ncbi.nlm.nih.gov/pubmed/280...

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  • Thanks also for this report. It just makes you wonder when people complain that they aren't improving on levothyroxine that aren't believed but instead probably given anti-d's or other prescritpions for the symptoms.

    Do the Endocrinology Association not read any Research papers?

  • Thanks for posting this article and the last one helvella. Are we now justified in saying that something is drastically wrong with the generic Levothyroxine now being used in UK?

  • If we had the specific results from the products available in the UK, then quite possibly. I can't see us getting them in a hurry even if they showed nothing of concern.

  • I think if I was checked out properly there would be a lot found to be wrong, but there has definitely been a big cover-up of what went wrong with Mercury Pharma in the beginning. So grateful for all the information you uncover for us helvella.

  • Would they find impurities in NDT as well?

  • That is a very good question.

    My guess (and that is all it is) is that there would very likely be a host of compounds found in extremely small quantities. Some would be the same as were found in levothyroxine, others different.

    Comparison of the lists from levothyroxine and desiccated thryoid might help to identify good and bad guys among them.

    At present we have extremely meagre understanding of the compounds present in desiccated thyroid beyond the main ingredient and excipients and the claimed T4 and T3 levels.

  • helvella That is most interesting Rob. Is anyone likely to do it?

  • Wouldn't be surprised if somewhere in the vaults of Armour (and their inheritors), RLC (Nature-Throid), or whoever there is some very interesting information.

    Can't imagine anyone else having the time and funds to do the work - even if they have the interest.

  • Thank you. I will not go overboard with any of these vegetables. I guess anything in moderation is OK.

  • One of the authors of this paper, Roland Reischl, has responded to my email prompted by TSH110

    thank you for your feedback and for your questions! Indeed this shows us that our work is relevant to people in the field.

    The method described in the paper focuses on the analysis of impurities generated by a specific synthetic approach linked to USP procedure 2. Nevertheless, the analysis via reversed phase chromatography and mass spectrometric detection will allow the identification of other impurities as well.

    In our work we identified molecules below 0.3% and above 0.01% of the main molecule levothyroxine, so it should be possible to use it also for other natural/dessicated products. Definitely the impurity profile can have an impact on the tolerability to sensitive patients.

    That researchers and patients both accept that low level impurities can have an impact, why then do those charged with managing treatment for the most part deny the possibility?

  • Wow, well done helvella!

    That sentence Definitely the impurity profile can have an impact on the tolerability to sensitive patients. is like music to the ears.

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