Is it Acceptable to Mix Extract-Batches in order to Improve Batch-to-Batch Consistency?

A revision of the "Questions & answers on quality of herbal medicinal products/traditional herbal medicinal products" document was published on the website of the European Medicines Agency (EMA) on 1 February 2024.

Two new questions have been added to the revised document, some questions have been changed and those questions that were already covered in the revised quality guidelines have been deleted.

The following questions have been added:

  • Question on production: "Is it acceptable to mix batches of 'other' extracts in order to improve the batch-to-batch consistency?"
    "Yes, it is acceptable to mix batches which are compliant with the release specification. However, it is not acceptable to use as criterion the content of an analytical marker alone, as this would resemble the manufacture of a quantified extract. Also, chromatographic fingerprints have to be used to justify mixing and to demonstrate the benefit of such a step with regards to the extract in its entirety. Moreover, the natural variability should be considered. It is not acceptable at all to mix batches which do not comply with the release specification in order to achieve a compliant pooled batch."

  • Question on water quality: "For the manufacture of herbal extracts, water complying with the Ph. Eur. monograph Water for preparation of extracts may be used. In the case of liquid extracts, this water would be part of the herbal medicinal product. In contrast, Ph. Eur. requires for the preparation of medicines the use of purified water. Is it therefore required to use purified water for the manufacture of liquid extracts?"
    "No. The extraction solvent is integral part of the herbal substance and not considered as an excipient. Therefore, it is acceptable to use water for preparation of extracts in the manufacture of liquid extracts, which are used as such in herbal medicinal products."

More details can be found in the Q&A document on the EMA website.

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