Stability testing of
Active pharmaceutical ingredients
Hua YIN
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CPH training | January 2012
References
This presentation make reference to:
API Stability
Lynda Paleshnuik. Assessment workshop. Copenhagen January 2010.
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CPH training | January 2012
References
 Generics Guideline
 Stability Testing of APIs and FPPs -- WHO Stability Guide in TRS953
(2009) Annex 2:
 ICH Q1(A, B, C, D and E)
 Variation Guidance Appendix 4 (Stability Requirements for Variations)
(TRS 943)
Guideline on stability testing for applications for variations to a marketing
authorization (EMA 2011)
 FDC guideline-- TRS 929 Annex 5 (appendix 3, Table A.1)
 Good storage practices: TRS 908
 FDA, EMA—stability for existing API and FPP
For PQP, when there are contradictions, the Generic quality guideline prevails
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CPH training | January 2012
Stability –purpose
 "Provide evidence of how the quality of an API or FPP varies with time
under the influence of a variety of environmental factors such as
temperature, humidity and light"
 "Study of product-related factors that influence its quality, for example,
interaction of API with excipients, packaging materials. In fixed-dose
combination FPPs (FDCs) the interaction between two or more APIs also
has to be considered.
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CPH training | January 2012
API Stability –purpose
 Understanding of the molecule
 Validation of analytical methods
 Selecting packaging
 To establish a re-test period for the API. In exceptional cases, e.g. for
unstable APIs, a shelf-life is given.
 To establish storage conditions.
 To establish/justify specification limits--derived from a consideration of
available stability data
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CPH training | January 2012
Overview
 Stress Testing
 Stability indicating method
 Accelerate and long term
 Evaluation
 Stability Commitments
 Examples
 Common Deficiencies
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CPH training | January 2012
API Stress Studies
Stability testing under conditions exceeding those used for accelerated testing.
Used to:
 establish the inherent stability characteristics of the molecule
 establish the degradation pathways
 identify the likely degradation products
 validate the stability indication power of the analytical methods
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CPH training | January 2012
API Stress Studies
The information can be used in:

Formulation development

Manufacturing process development

Ensure proper selection of stability-indicating analytical techniques

Preparing reference material of identified degradation products

Degradation pathways elucidation

Selection of proper packaging
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CPH training | January 2012
API Stress Studies
 When available, it is acceptable to provide relevant data published in the
scientific literature to support the identified degradation pathways and
products.
 If “protect from light” is stated in one of the officially recognized
pharmacopoeia for the API, it is sufficient to state “protect from light” on
labeling, in lieu of photostability studies, when the container closure
system is shown to be light protective.
 When no data are available, stress testing should be performed.
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CPH training | January 2012
API Stress Studies
How to design stress studies?

No detailed stress testing strategy in Guidelines, i.e.
experimental conditions and duration may need to be varied depending on the
nature of the drug substance

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Generic guideline refers to FDC guideline appendix 3, table A.1 (TRS
929 Annex 5) -- as examples
CPH training | January 2012
API stability
Stress testing – Typical Stress conditions
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CPH training | January 2012
API Stress Studies
 1 API batch (pilot scale, representative of the production batch)
 Should include:
 Effect of temperatures
 Humidity
 Acid and base hydrolysis
 Photolysis (generally as per Q1B)
 Oxidation
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CPH training | January 2012
API Stress Studies
 How much stressing is enough ?
 10-30% loss of API assay (FDC guideline, as well as Generic
guideline)
 between 5% to 20% degradation (some literature)
 approximately 10 % degradation is optimal for method validation (as
assay limits are normally 90-110%)
 balance between "purposeful degradation" and irrelevant artifacts (e.g.,
secondary degradation products).
 degradation products not formed during accelerated or long-term stability
studies--need not always to be examined
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CPH training | January 2012
Stress studies:
Approach for Assessment: DO
- Check if data is provided, either generated by
supplier/applicant or from literature references
- Check for compendial statement, “protect from light”.
- Check that conditions are adequate
- Check the extent of degradation
- ≈10% = adequate degradation
- little or no degradants : verify if conditions are "harsh" enough. If
yes, the API is considered stable.
- Conclude on the degradation pathways, stability nature of the API
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CPH training | January 2012
Stress studies:
Approach for Assessment : DON’T
- spend excessive time with degradants generated in stress studies if they
are not formed in practice.
The impurities/degradants that must be closely investigated are those
appearing when stored at long-term and accelerated conditions at
greater than (or approaching) the identification threshold (the limit of
individual unknowns, 0.1%).
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CPH training | January 2012
Stability indicating method
 Without analytical methods it is not possible to know what has happened
during stability
 Assay
 Impurities/Degradation Products
 Chiral Purity
 Dissolution
 Preservative Content
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CPH training | January 2012
Stability indicating method
 This is a chicken and egg problem
– need analytical methods to analyze stability data
– need stability information to validate methods
 Start with preliminary method based on what is known of drug substance
– can determine content of drug substance, can separate the known or
expected degradants
 Use preliminary method to analyze stress stability studies
– evaluate ability of method to separate degradants i.e the specificity -confirm peak purity, mass balance
 Use this information to modify/improve method
 stability studies and analytical method development work together
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CPH training | January 2012
API Stability:
Stability protocol
 Number of batch(es) and batch size(s)
 Container closure system (s)
 Conditions of storage
 Tests and acceptance criteria (reference to test methods)
 Testing frequency
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CPH training | January 2012
API Stability:
Selection of Batches
Primary Batches: API batches used in stability studies to establish retest
period.
Prequalification: 3 batches of at least pilot scale (as per Q1A).
*Pilot batches must be of the same synthesis route, and with method of
manufacture and procedure which simulates the final process for production
batches.
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CPH training | January 2012
API Stability:
Container Closure System
 Should be the same or simulate the container proposed for
storage/distribution unless justification provided (ie container used in
studies is less than or equally protective compared to proposed container)
 A functionally similar container may be used
to mimic the cardboard or plastic drum that is
usually used to store raw material
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CPH training | January 2012
API Stability:
Tests and acceptance criteria
Specifications: test attributes susceptible to change:
 Appearance (description)
 Degradation (related substances)
 Assay
 Enantiomer
 Plus others susceptible to change, e.g. LOD
Methods:
 If same as in API specs, cross-reference
 If different, provide methodology and validation data for impurity and
assay methods
 Methods should be stability-indicating
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CPH training | January 2012
API Stability:
Tests and acceptance criteria
Other parameters to be monitored
 The API is low solubility and micronized, and the FPP is low dose
(common for RH products). PSD is critical.
PSD stability should be monitored for potential increase in particle size
(due to discreet particles or particle agglomerates).
 For a low solubility API, if there is evidence that polymorph stability may
be an issue, polymorphic form should be monitored during stability
studies.
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CPH training | January 2012
API Stability: Storage Conditions
Climatic Zones

Zone I: 21°C/45% RH

Zone II: 25°C/60% RH (subtropical)

Zone III: 30°C/35% RH(hot/ dry)

Zone IVA: 30°C/65% RH (hot/ humid)

Zone IVB: 30°C/75% RH (hot/ very humid)
Long term stability studies should cover all climatic zones if possible
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CPH training | January 2012
API Stability: Storage Conditions
 The required long-term storage conditions for APIs in the Prequalification
Programme:
 30ºC±2ºC/65%±5%RH or 30ºC±2ºC/75%±5%RH.
 Alternative conditions should be justified, e.g. storage at 30ºC is
inappropriate for the API. (e.g. Tenofovir disoproxil fumarate )
 If no stability studies at 30ºC, commitment to commence studies at
30ºC on the next 3 production scale batches, and to revise the storage
condition/retest period, if applicable
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CPH training | January 2012
API Stability: Storage Conditions
Storage
condition
Months
3
6
9
12
18
24
36
48
60
30ºC/75% or
30ºC/65%
x
x
x
x
x
x
x
x
x
40ºC/75%
x
x
x
x
x
x
x
x
x
x
25ºC/60%
For storage in a refrigerator
5ºC±3ºC
x
x
25ºC/60% or
30ºC/65% or
30ºC/75%
x
x
x
x
x
For storage in a freezer
-20 ºC±5ºC
x
x
x
x
x
One batch at 5ºC, 20ºC, or 30ºC to address the effect of short-term excursions
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CPH training | January 2012
API Stability: Testing Frequency
Long term:
Year 1: every 3 months; Year 2: every 6 months
Subsequent years: annually
Accelerated:
Minimum three points including t0 and tfinal, e.g 0, 3, 6.
Intermediate:
Four points including t0 and tfinal, e.g 0, 6, 9, 12.
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CPH training | January 2012
Minimum data requirements at time of submission
Accelerated
Storage
Relative humidity
Minimum time period
temperature (ºC)
(%)
(months)
40±2
75±5
6
*
*
65±5 or 75±5
6
Intermediate *
Long-term
30±2
*Where long-term conditions are 30ºC±2ºC/65%±5%RH or 30ºC±2ºC/75%±5%RH,
there is no intermediate condition.
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CPH training | January 2012
What are expected in the stability reports?
 General information: name, manufacturing sites, date of manufacturing of
the API; batch number, batch size, container/clourse
 Stability data in tables or graphs or both
 Evaluation
– Justify parameters tested (OoS, OoT discussion)
– Statistical analysis, if necessary
 Conclusions
– Proposed retest date for drug substance
– Proposed shelf-Life, if applicable
– Proposed storage condition
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CPH training | January 2012
API Stability: Evaluation
 Collect information
 The innovator (e.g. EPAR)
 Literature
 Prequalified products
 APIMFs
 Confirm the number of batches, batch size, packaging, storage conditions,
test frequencies, specification.
 Review the stability results.
 For an API, “significant change” is failure to meet the specification for
any parameter
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CPH training | January 2012
API Stability: Evaluation
 Begin with any significant change at the accelerated condition, and
 the intermediate condition, if appropriate
 then, review the trends and variability of the long-term data
 Establish re-test and storage condition
 Refer ICH Q1E appendix A decision Tree for any extrapolation
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CPH training | January 2012
API Stability: Evaluation
Extrapolation of data:
Extend the retest period or shelf life beyond the period covered by longterm data
A retest period or shelf life granted on the basis of extrapolation should
always be verified by additional long-term stability data as soon as these
data become available.
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CPH training | January 2012
API Stability: Evaluation

No significant change at accelerated condition (6 months )

Little/no change and little/no variability for accelerated and long term data

statistical analysis is unnecessary
intended for storage at
25ºC or 30ºC
intended for storage at
refrigerator 2-8 ºC
Y= 2X
but NMT X + 12 months
Y= 1.5X
but NMT X + 6 months
X= Period covered by long-term data
Y= proposed retest period or shelf life
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CPH training | January 2012
API Stability: Evaluation
 No significant change at accelerated condition (6 months )
 Change and/or variability observed for accelerated and/or long term
data
 Extrapolation may be proposed by providing Statistical analysis and/or
relevant supporting data *
* Satisfactory long term data from development batches (with a closely
related formulation, packaged in similar container closure system, smaller
scale than the primary batches)
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CPH training | January 2012
API Stability: Evaluation

Significant change at accelerated condition, but

No Significant change at intermediate condition

Extrapolation may be proposed by providing Statistical analysis and/or
relevant supporting data
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CPH training | January 2012
API Stability: Evaluation

Significant change at accelerated condition, And

Significant change at intermediate condition

No extrapolation is allowed

In addition, a shorter retest period or shelf life than the period covered by
long term data could be called for.
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CPH training | January 2012
API Stability: Evaluation
For products intended for storage in a refrigerator (no intermediate)

Significant change at accelerated condition

No extrapolation is allowed

In addition, a shorter retest period or shelf life than the period covered by
long term data could be called for.

If significant change occurs within the first 3 months' accelerated testing, a
discussion should be provided to address the effect of short –term excursions
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CPH training | January 2012
API Stability: Evaluation
Definition: re-test period
The period of time during which the API is expected to remain within its
specification, provided that the API has been stored under the defined
conditions.
After this period
Re-tested for compliance with the specification and then used immediately.
A batch of API can be re-tested multiple times and a different portion of the
batch used after each re-test, as long as it continues to comply with the
specification.
For most substances known to be labile, it is more appropriate to establish a
shelf life than a re-test period. Example: rifampicin
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CPH training | January 2012
API Stability: Stability Commitments
 Primary stability study commitment
When available long-term stability data on primary batches do not cover the
proposed re-test period.
 Commitment stability studies
The long-term stability studies on at least three production batches.
To determine that the API remains and can be expected to remain within the re-test
period in all future batches.
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CPH training | January 2012
API Stability: Stability Commitments
1) A stability commitment is required when long term data does not
cover the proposed re-test period.
“The Applicant should undertake in writing to continue long-term testing
of <INN of API> for a period of time sufficient to cover the whole
provisional retest period and to report any significant changes or out-ofspecification results immediately to WHO for the following batches :
<Batch numbers, manufacturing dates, batch size, primary packing
materials >”
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CPH training | January 2012
API Stability: Commitments
2) A stability commitment is required when data was not provided on
three production scale batches.
“Since stability data on three production scale batches were not provided
with the application, the remaining number of consecutive production
scale batches should be put on long-term stability testing. Any significant
changes or out-of-specification results should be reported immediately to
WHO.
The approved stability protocol should be used for commitment batches.”
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CPH training | January 2012
API Stability: Commitments
 Stability protocol should follow the same as primary batches but may
change in batch numbers, batch size. Any differences in the stability
protocols used for the primary batches and those proposed for the
commitment batches should be scientifically justified.
 In general, we do not request submission of the commitment results. But
to report immediately for any OOS, OOT. The reports should be available
for inspection. Therefore, a signed and dated commitment is requested and
should be recorded.
 When submitting post approval variations, e.g. extension shelf life, change
in batch size, the data of commitment batches may be requested.
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CPH training | January 2012
API Stability
Statements/Labelling
 All containers should be clearly labeled with at least:
 name of the material
 batch number
 expiry date or retest date
 specified storage conditions
 Name and address of the manufacturer (main generic G)
 Recommended labeling statements provided in Appendix 3 of the New
Guide.
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CPH training | January 2012
 b :"protect from moisture" should be added if applicable
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CPH training | January 2012
Example #1
API Re-test and Shelf-life
Problem: The applicant has proposed a 12 month
re-test period and a 48 month expiration period.
They have provided data to support the re-test period,
but not the shelf-life. Now what?
Approach: Except in exceptional situations, the shelf-life
is not required and is considered an extra assurance. Since a re-test period
is defined, the applicant must re-test the API immediately prior to its use
once the re-test period has been exceeded. The re-test period, which is
supported by data, is approved.
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CPH training | January 2012
Example #2
No Accelerated Data
Problem: Data is provided over the retest period
at long-term conditions. No data is provided at
accelerated conditions. The applicant argues that
accelerated data is not necessary because long-term data
covers the proposed retest period.
Approach: Accelerated data is not only to support extrapolation, it is also
to cover excursions outside the long-term storage conditions. Accelerated
data is always required to support a retest or shelf-life period.
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CPH training | January 2012
Example #3
Extrapolation
 6 months at 40ºC/75% data: no significant change observed
 18 months data at 30 ºC75%, show little change and little variability.
 What 's the maximum allowed retest period and storage condition?
 X=18, the longest period allowed is up to 2X ( 36 months), but Not more
than X + 12= 30 months
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CPH training | January 2012
Common Deficiencies
These deficiencies are commonly encountered and lead to questions and
delays in approval of a re-test period:
1. Failure to state the size of the lots used in the trial.
2. Failure to describe clearly the packaging used in the trial and to confirm
whether it is identical to the proposed packaging.
3. Failure to accumulate stability data on the required number of lots.
4. Failure to define accurately the temperature and humidity conditions
applied during the trial. ±2◦C, ±5%RH
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CPH training | January 2012
Common Deficiencies
5. Failure to fully describe test methods.
6. Failure to provide validation of analytical methods.
7. Expression of results as passes test or similar when a quantitative figure
would be available.
8. Failure to include quantitative or semiquantitative determinations of the
content of degradation products, or to provide only total content rather
than values for individual impurities.
9. Use of an HPLC assay procedure to detect impurities without validation
for the purpose.
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CPH training | January 2012
Common Deficiencies
10. Failure to comment or conduct additional tests when there is a lack of
mass balance between the formation of degradation products and the loss
of the active substance. For example, are the assay procedures sufficiently
specific? Is the API volatile? Is it adsorbed on to the container wall?
11. Failure to conduct additional tests to investigate the significance of
obvious alterations in the characteristics of the product. For example a
distinct change in the colour of the product may necessitate additional
investigation for degradation products.
12. Failure to discuss any OoS or OoT results
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CPH training | January 2012
Common Deficiencies
13. Failure to include information on the physical characteristics of the
product during storage, such as particle size etc when considered critical
attributes.
14. Failure to provide results from intermediate time stations to facilitate
assessment of any trends in the parameters measured, when significant
change is noted at accelerated conditions.
15. Attempting to extrapolate data obtained in the trial beyond reasonable
limits.
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CPH training | January 2012
Thank you for your attention!
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CPH training | January 2012