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Note:  This document expresses Dr. Jenke’s personal views and opinions and is not a position established and supported by Triad Scientific Solutions LLC.  This document is not professional advice and does not constitute a professional service provided by either Dr. Jenke or Triad Scientific Solutions.       

January 2018 - Current Topic

              Thoughts on Extractable Metals from Packaging





The safety aspects of elemental impurities in finished drug products is a “hot topic” in the pharmaceutical community and guidelines such as ICH Q3D and USP <232> provide directions on how to assess finished drug products for such impurities.  Although a drug product’s packaging system is noted as a potential source of elemental impurities, guidelines have not been established for assessing packaging systems, or their materials and components of construction, for their potential to contribute leached elements in general, and metals in particular, to packaged drug products. 


In considering the issue of extractable metals from packaging, the first necessary activity is to expand the playing field.  By this I mean that both ICH Q3D and USP <232> address only one aspect of the potential product impact of extracted metals, patient safety.  It has been well-established that extracted metals can also impact the quality of a packaged drug product, affecting such product properties as potency, efficacy, stability and ability to meet quality specifications.  While the Permissible daily exposure (PDE) values provided in both Q3D and <232> adequately address potential patient safety issues, they are meaningless as limits or thresholds for potential quality effects.  While the list of elements in both Q3D and <232> reflect those elements of greatest toxicological concern, the list is not comprehensive in terms of elements that could or do adversely affect product quality.  Thus, if one is to address the full risk that extracted metals represent, they must go beyond the guidance and insight provided by both Q3D and <232>.


At a high level, two circumstances must exist for a packaging system to be a relevant source of elemental impurities in a packaged drug product:


  1. Packaging systems must contain sources of elemental impurities in the first place, and

  2. Those elemental impurities that are present in the packaging must leach out of the packaging and into the drug product during system/product contact.


Considering these circumstances, a team of authors representing the Extractables and Leachables Safety Information Exchange (ELSIE) and International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) published a review of published extractable metals data for plastic and glass packaging systems and concluded that:


  1. Unless the elemental entities are parts of the materials themselves (for example, SiO2 in glass) or intentionally added to the materials (for example, metal stearates in polymers), their incidental amounts in the materials are generally low.

  2. When elemental entities are present in materials and systems, generally only a very small fraction of the total available amount of the entity can be leached under conditions that are relevant to packaged drug products.


These conclusions reinforce what I believe is a common opinion among E&L experts, which is that “there is generally a low risk of adverse product effects arising from metals leached from packaging systems” and thus that “monitoring or qualifying packaging systems with respect to extractable metals is, in many circumstances, unwarranted and unnecessary, especially if the packaged drug product is going to be assessed for elemental impurities anyway”.   While I would not necessarily disagree with this point, I would make two counterpoints.  Firstly, it is my opinion that while the dataset supporting this conclusion was comprehensive, it reflected only that information which had been published at the time the review was written.  Personally, I am not 100% convinced that the information contained in the article is sufficient to be the sole basis of such an impactful policy as “no extractable metals testing required for packaging”.  Perhaps a larger and more complete database of information will allow the scientific community to draw a conclusion, one way or the other, with respect to extractable metals testing of packaging.


The second point I would like to make is that “low risk is not no risk”.  In fact, certain elements in certain circumstances can leach from packaging and can have an undesirable impact on a key product attribute.  I do not know how to properly respond to individuals who ask “in the absence of testing, how are you going to reveal known or currently unknown and unanticipated product – leached metal interactions?”.  But I know this: no one wants to be the next case study that everybody is talking about on the E&L circuit in terms of “we do E&L testing to prevent this from happening”.


Let us imagine the situation where it has been established that extractable metals from packaging is such a low risk that packaging systems and/or their materials and components of construction do not have to be screened for extractable metals.   The question then comes up “how will this conclusion be captured in the “official” guidelines, guidances and standards?” For example, as it currently stands, USP <661.1> contains mandatory extractable metals testing for polymeric material used in packaging.  Would it be proper for the USP in either <661.1> or its companion document <1661> to state that “extractable metals testing is not necessary” by either directly making this statement or indirectly by removing extractable metals testing?  My opinion is that this would not be proper because it is not <661.1> that establishes the need to consider metals leached from packaging in the context of elemental impurities.  Rather, it is Q3D and <232> that establish the packaging system as a potential source of elemental impurities and requires that packaging systems be assessed to control elemental impurities.  Thus, if it were ever decided that the risk of extracted metals from packaging (or packaging material and components of construction) is so low that testing packaging (or materials or components) for extractable metals is not required, the proper place to capture this point would be the very documents which raise the issue in the first place, meaning Q3D and <232>.   In such a circumstance while it might be proper for both Q3D and <232> to mention packaging as a potential or theoretical source of elemental impurities, it would also be necessary for the same documents to note that the risk is low and thus that routine screening is not required.


Alternatively, let us imagine a situation where it has been established that the risk of extracted metals becoming elemental impurities is sufficiently high that packaging systems and/or their materials and components of construction must be screened for extractable metals.  In this case, four questions are relevant:


1.    What articles should be testing? (e.g., materials, components, and/or packaging),

2.    How should the articles be tested? (e.g., digestion or extraction and under what conditions),

3.    What elements should be targeted in the testing?  (e.g., “The Big Four”, the “entire periodic table” or something in-between),

4.    How should the results of the testing be reported and interpreted?  (e.g., specification limit, reporting threshold and at what level).


At times I think it would truly require the wisdom of Solomon to provide answers to these four questions which are (a) scientifically valid, (b) practically implementable and (c) acceptable to the many and varied stakeholders who have a stake in this subject.  For those individuals and organizations who are trying to find that wisdom, I say good luck and god-speed and I thank them for their efforts.






      Spring 2017 - Current Topic         




Note:  This document expresses Dr. Jenke’s personal views and opinions and is not a position established and supported by Triad Scientific Solutions LLC.  This document is not professional advice and does not constitute a professional service provided by either Dr. Jenke or Triad Scientific Solutions.   



When members of the E&L community gather to develop standards, guidelines and best demonstrated practice recommendations, there are three principles they should obey:


  1. The standards must be based on “good science”,

  2. The standards must be effective and efficient, and

  3. The standards must fit every conceivable circumstance well.


It is the inability to achieve these principles that makes the generation of standards, guidelines and recommendations so frustratingly challenging.


Consider the last principle, for example.  It is intuitively obvious in a diverse field such as pharmaceuticals that this principle is impossible to achieve as it is clear that a rigorous standard (which is specified set of tests coupled to a specified set of acceptable test results) cannot fit all the diverse circumstances equally well.  It is the same problem as trying to design a glove that fits every human being.  If the underlying purpose of the glove is “to keep one’s hands warm”, then a standardized glove can be designed that will address this requirement, to some degree, for most people.  However, because the glove must keep everybody’s hands warm, it is logical that there will be design tradeoffs which will mean that while it keeps everyone’s hands warm, it does not keep everyone’s hands as warm as they would personally like it.  Furthermore, there may be other trade-offs, such as “these gloves are not very sexy”, or “these gloves do not match my coat” or “these gloves make my hands itch”.


While the challenges in making standards that are generally applicable in the greatest number of circumstances are considerable, this is not the point that I want to address in this discussion.  Rather, I want to address the challenges associated with good science.


Good science suffers from with the same problem as designing a standardized glove.  As good scientists, we learned and we understand that there are very few universal scientific truths; rather, a scientific truth is a truth only under the rigorously defined set of circumstances upon which it is based.  When we perform an experiment and draw a conclusion from that experiment, we understand the conclusion is only perfectly valid for the set of defined experimental circumstances we started out with.  Extension of that same conclusion to other circumstances involves a certain measure of risk, specifically the risk that in changing the circumstances we have invalidated (knowingly or unknowingly) some fundamental principle that defines the applicability of our conclusions.   Thus, we understand that there is an inherent trade-off when we make scientific generalizations and put them into standards, guidances and recommendations.  That is, we sacrifice some of the good in good science for the sake of providing a direction that is generally right in the greatest number of circumstances.


The challenge we face as practitioners of good science is not in recognizing good science per say but recognizing the boundaries that differentiate between good science properly applied and good science improperly applied.  When we are tempted to use a standard, or leverage a “rule of thumb” or “do this because everybody else is doing it”, as good scientists we must ask ourselves “am I taking a good idea in certain circumstances and applying it to the wrong circumstances?”.   If the answer is yes, then surely this is as bad as using “bad” science in the first place.


Let me illustrate this with an example.  I use this as an example not because it a particularly bad practice but because it effectively illustrates my point.  The following, taken from the PQRI OINDP Best Practice recommendations, is well known and commonly applied in the E&L community.


  1. The Working Group recommends that analytical uncertainty be evaluated in order to establish a Final AET for any technique/method used for detecting and identifying unknown extractables/leachables.

  2. The Working Group proposes and recommends that analytical uncertainty in the estimated AET be defined as one (1) standard deviation in an appropriately constituted and acquired Response Factor database OR a factor of 50% of the estimated AET, whichever is greater.


The question I would ask you to consider is “where is the good science and the not so good science in these recommendations?”


Here is my answer.  It is well known that response factors will vary among the universe of compounds that could be extractables and leachables.   Thus, it is good science that a general concept such as the AET, which presumably is applicable to all possible extractables/leachables, take this variation into account.  Furthermore, we all understand that basing actions on relevant and sufficient data is the cornerstone of good science, and thus that the requirement to consider “an appropriately constituted and acquired Response Factor database” is a requirement to do good science.  However, it must be obvious that the direction to universally “use a factor of 50%” is not necessarily good science.  While the derivation of the 50% is itself good science, as it was based on a response factor database (which is somewhat small in the context of the databases available today), it is obvious that the 50% is only relevant for the compounds in that database and the analytical method with which the data was generated.   Universal and unquestioned application of the factor of 2 rule to compounds that were not in the original database and to analytical methods other than the method used to generate the data is not the best science; rather, it is poor science, not because the science itself is bad but because the good science aspects are being applied out of context.  


To a good scientist, arguments such as “it is better than nothing” or “everybody else is doing it” are inexcusable.  Certainly, the idea that “it is better than nothing” has to be examined objectively and harshly.  The improper application of science is not guaranteed to be better than doing nothing because it is not the case that the improper application of science will always make things better.  In fact, the history of improper application of good science is littered with examples of bad outcomes derived from applying good sciences incorrectly. 


Listen, nobody said doing good science was easy.  We understand that part of the driving force for recommending that the factor of 2 be universally applied is that back then few people could access a database.  Thus, it was nearly impossible to practice the good science required in the recommendation and people, rather than do nothing, gravitated to the other part of the recommendation.  However, today, it is virtually impossible to run into a reputable E&L laboratory that is not eager to talk about their database.  Thus, in this case, our ability to do good science has finally caught up with our responsibility to do good science.  It is proper that we accept that responsibility and be held accountable for meeting that responsibility.


This is true not only to adjusting the AET for analytical uncertainty but in numerous other places where our current capabilities enable our ability and address our responsibility to practice and preach a higher degree of good science than has ever been possible.  Currently applied recommendations, standards, guidelines and practices must be adjusted, as appropriate, to leverage this new and higher degree of good science and new recommendations, standards and guidelines must be drafted to reflect this new and higher degree of science.  We aspire to better science because we are capable of better science.  More importantly, if we are going to talk the talk, we best start walking the walk. 

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