1. INTRODUCTION:

Stability testing of a drug substance or a finished product is a vital part of the data package submitted in support of new drug applications or marketing authorisations. The principle ethos of stability testing is to provide evidence to a regulatory body that the quality of the product or raw material doesn’t vary with time, under the influence of a range of different factors including temperature, humidity and light. With the evolution of drug development to include whole new classes of molecules, the application of the International Conference on Harmonisation (ICH) guidelines remains the same but the level of technical complexity in designing stability programmes that are fit for purpose has increased dramatically. Therapeutic agents that include proteins and peptides or monoclonal antibodies pose a different set of practical challenges in providing data which meets the needs of both the regulatory authorities and the developers of these drug products.¹

Stability Testing is defined as how well a product retains its quality over the life span of the product. The purpose of stability testing is to provide evidence on how the quality of a drug substance or drug product varies with time under the influence of a variety of environmental factors such as temperature, humidity, and light, and to establish a re-test period for the drug substance or a shelf life for the drug product and recommended storage conditions.

Stability testing and monitoring is a critical step in drug research, development and manufacturing. It impacts the safety of drugs and how pharmaceuticals are produced, packaged, labeled, stored and sold. Therefore stability testing is strictly regulated and heavily enforced by FDA and other agencies. Guidelines require to monitor degradation products over storage time to assure that the integrity of product remains unchanged throughout its shelf life. However, stability testing is a complex process and despite of the fact that guidelines have been available since quite some time from ICH and other organization, industry still has problems to meet the expectations of inspectors.^2,3

At its simplest, stability testing can be considered in two steps, establishing potential degradation pathways and then verifying which pathways actually occur under normal storage conditions. This involves applying theory (knowledge of organic functionality and reactivity) and some practical experimentation, usually using “forced” or stress storage conditions of temperature, humidity, photolysis, hydrolysis, and oxidation. Verification involves setting our drug substance or product down on stability using accelerated, intermediate, and real-time storage conditions and analyzing them after specified storage periods. This is usually administrated using a stability protocol.

There are several factors that influence physical stability. For example, the physical form of the drug substance and excipients, the packaging system used and the prevailing environmental conditions when the product is stored, shipped, and used in the intended licensing territory.⁴

Physical processes are one of the four main modes of degradation, namely chemical, physical, biological, and microbiological. Chemical and physical modes can be closely linked as chemical degradation may affect physical properties and functional behavior.

Chemical stability is reasonably well understood as a mechanistic understanding of the potential degradation reactions is possible, hydrolysis, oxidation, photolysis, and isomerization being the most common.⁵

1.2. Stability Testing and Pharmaceutical Products:^6,7

The stability of finished pharmaceutical products depends on several factors. On the one hand, depends on environmental factors such as ambient temperature, humidity and light. On the other hand, it depends on product- related factors such as the chemical and physical properties of the active substance and pharmaceutical excipients, the dosage form and its composition, the manufacturing process, the nature of the container-closure system and the properties of the packaging materials.

The stability program and subsequent testing of both the Active Pharmaceutical Ingredient (API) and the finished product plays a pivotal part in the drug development pipeline. It is crucial that any programme undertaken is sustainable and is also compliant with current regulations of the Medicines and Health Regulatory Authority (MHRA), Food and Drug Administration (FDA) or other competent regulatory organisations. Stability testing provides the scientific evaluation of both API and finished product in determining the shelf life consideration for the label and governs also the suitability of any formulations for clinical trial to be suitably active for the duration of any intended dosing regime.⁶

The scientific principles in stability testing have not changed significantly in recent years but there is now a far greater understanding of the complexities and complications that biopharmaceuticals intrinsically carry.⁷

The predominance of pharmaceutical products currently licensed to the marketplace are New Chemical Entities (NCEs) or more generally referred to as small molecule API’s. While stability testing for small molecule drugs is well established, its counterpart for NBE derived products is still evolving and the complexity of both the NBE and the process by which it is manufactured dictates that a very different view must be taken when considering stability testing. ⁸

1.3. Critique:

Stability testing for pharmaceutical products has now been harmonized globally. All Pharmaceutical products must undergo defined specific testing conditions in accordance to local climatic conditions.

With the ICH guideline Q1A (R2) for stability tests which was finalised in August 2003, and revised in 2005 (withdrawal of the chapter Q1F, which defines additional stress testing conditions in zones III and IV) new changes have taken place. With the withdrawal of chapter Q1F, the 10 member ASEAN countries have introduced their independent technical dossier related to the ICH guidelines and have adapted the testing conditions to suit their own climatic conditions. The enforcement of the ASEAN ICH guidelines into the ASEAN countries is currently in progress.⁹

The example of the ASEAN countries clearly demonstrates that the testing standard will become more intensive and specific. Individual advances from various countries to look into testing protocols under varying climatic conditions or more toughened testing conditions are in discussion.

Once again the pharmaceutical industry sets new quality standards for the stability testing of pharmaceutical goods. It is a challenge for pharmaceutical companies but also a challenge to suppliers of testing equipment, to be prepared for the demands of tomorrow.

After the latest revision and implementation for ICH stability testing the actual conditions are as now regulated in chapter Q1A (R2) for climatic stability testing and in chapter Q1B for photo stability testing (unchanged). The introduction of the ASEAN ICH guidelines which are defined as zone IVb created new regional testing conditions for the long term stability tests to be carried out in the 10 ASEAN (Association of South East Asian Nations). ^9,10

This leaves now following climatic zones (Grimm, 1980). It is now up to individual countries located in zone IV to decide whether they wish to join the newly created climatic zone IVb or to follow the testing conditions of zone IV defined by WHO / ICH.

• Zone I: Temperate zone

• Zone II: Mediterranean/subtropical zone

• Zone III: Hot dry zone

• Zone IV: Hot humid/tropical zone

• Zone IVb ASEAN testing conditions hot/higher humidity

Chapter Q1A (R2) regulates the stability testing for long term testing at ambient, refrigerated and frozen storage conditions of pharmaceutical products. The testing conditions are displayed in table 1.

Table 1: Long Term Testing Conditions

Climatic zone	Temperature	Humidity	Min. duration
Zone I	21°C ± 2°C	45% rH ± 5% rH	12 months
Zone II	25°C ± 2°C	60% rH ± 5% rH	12 months
Zone III	30°C ± 2°C	35% rH ± 5% rH	12 months
Zone IV Zone IVb	30°C ± 2°C 30°C ± 2°C	65% rH ± 5% rH 75% rH ± 5% rH	12 months 12 months
Refrigerated	5°C ± 3°C	No humidity	12 months
Frozen	- 15°C ± 5°C	No humidity	12 months

Besides long term stability testing of various storage conditions, the ICH guidelines also requires accelerated testing conditions for all storage conditions (frozen, refrigerated and ambient) and an intermediate testing when the accelerated testing shows unacceptable deterioration (see table 2).

The idea is that stability tests should reliably indicate how and in what time the composition of a substance or packaged product changes under environmental conditions. This is done for the purpose of correctly determining and declaring the shelf life of substances, products and medications. In order to ensure that the process of making these determinations is carried out by uniform criteria worldwide, guidelines were developed, to be adhered to with regards to:

· Temperature,

· Humidity and

· Light,

And carried out in an identical manner. The existence of various climatic zones on the globe makes this uniformity a little complicated - as already explained. To meet today's demands, a climate cabinet should, where possible, be constructed to "replicate" all climatic zones. This is of particular importance for manufacturers of pharmaceutical products who export into various climatic zones. For these manufacturers, chambers such as the ones manufactured by BINDER are of interest, since they are able to "replicate" all climatic zones - and meet all international standards required for this purpose: they are in agreement with the pharmaceutical ICH guidelines and beyond this, the FDA, GLP/GMP etc.¹¹

2. Guidelines on Stabilty Testing:

2.1. ICH Guidelines:

There are many regulations surrounding the development, implementation and assessment of such programs. Without knowledge of these regulations, and how they are interpreted, stability testing can prove an extremely costly exercise, especially for the smaller sponsor. Generation of data is designed to give validation of the product shelf life, and it is critical that those assessing stability data make appropriate recommendations for product shelf life and formulation based on that data.

The latest revision of ICH Q1A - Stability Testing of New Drug Substances and Products, defines the purpose of stability testing as providing evidence on how the quality of drug substance or drug product varies with time under the influence of different environmental factors such as temperature, humidity, and light to establish a retest period for drug substance or shelf life for drug product and to recommend appropriate storage conditions.

A review of the current ICH Guidelines establishes that there are six documents which are specific in their application to the stability testing of pharmaceutical products and components both small molecule and biopharmaceutical.¹²

2.2. WHO Guidelines:

STABILITY TESTING:

Long-term and accelerated (and intermediate) studies undertaken on primary and/or commitment batches according to a prescribed stability protocol to establish or confirm the re-test period (or shelf-life) of an active pharmaceutical ingredient (API) or the shelf-life of a finished pharmaceutical product (FPP).

The purpose of stability testing is to 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.

Information on the stability of the API is an integral part of the systematic approach to stability evaluation. Potential attributes to be tested on an API during stability testing are listed in the examples of testing parameters. The re-test period or shelf-life assigned to the API by the API manufacturer should be derived from stability testing data.¹³

3. Stabilty Testing of Active Pharmaceutical Ingredient:

3.1 STRESS TESTING:

Stress testing of the API can help identify the likely degradation products, which, in turn, can help establish the degradation pathways and the intrinsic stability of the molecule and validate the stability-indicating power of the analytical procedures used. The nature of the stress testing will depend on the individual API and the type of FPP involved. For an API the following approaches may be used:

When no data are available, stress testing should be performed. Stress testing may be carried out on a single batch of the API. It should include the effect of temperature (in 10 °C increments (e.g. 50 °C, 60 °C, etc.) above the temperature used for accelerated testing), humidity (e.g. 75% relative humidity (RH) or greater) and, where appropriate, oxidation and photolysis on the API. The testing should also evaluate the susceptibility of the API to hydrolysis across a justified range of pH values when in solution or suspension.⁵ Assessing the necessity for photostability testing should be an integral part of a stress testing strategy. More details can be found in other guidelines.⁶ Results from these studies will form an integral part of the information provided to regulatory authorities.¹⁴

3.2 Selection of batches:

Data from stability studies on at least three primary batches of the API should normally be provided. The batches should be manufactured to a minimum of pilot scale by the same synthesis route as production batches, and using a method of manufacture and procedure that simulates the final process to be used for production batches. The overall quality of the batches 90 of API placed on stability studies should be representative of the quality of the material to be made on a production scale. For existing active substances that are known to be stable, data from at least two primary batches should be provided.^14,15

3.3 Container closure system:

The stability studies should be conducted on the API packaged in a container closure system that is the same as, or simulates, the packaging proposed for storage and distribution.

3.3.1 Specification:

Stability studies should include testing of those attributes of the API that are susceptible to change during storage and are likely to influence quality, safety and/or efficacy. The testing should cover, as appropriate, the physical, chemical, biological and microbiological attributes. Validated stability-indicating analytical procedures should be applied. Whether and to what extent replication should be performed will depend on the results from validation studies.¹⁵

3.3.2 Testing frequency:

For long-term studies, frequency of testing should be sufficient to establish the stability profile of the API. For APIs with a proposed re-test period or shelf-life of at least 12 months, the frequency of testing at the long-term storage condition should normally be every three months over the first year, every six months over the second year, and annually thereafter throughout the proposed re-test period or shelf-life. At the accelerated storage condition, a minimum of three time points, including the initial and final time points (e.g. 0, 3 and 6 months), from a six month study is recommended. Where it is expected (based on development experience) that results from accelerated studies are likely to approach significant change criteria, increased testing should be conducted either by adding samples at the final time point or by including a fourth time point in the study design. When testing at the intermediate storage condition is called for as a result of significant change at the accelerated storage condition, a minimum of four time points, including the initial and final time points (e.g. 0, 6, 9 and 12 months), from a 12-month study is recommended.¹⁶

3.3.3 Storage conditions:

In general an API should be evaluated under storage conditions (with appropriate tolerances) that test its thermal stability and, if applicable, its 91 sensitivity to moisture. The storage conditions and the lengths of studies chosen should be sufficient to cover storage and shipment. Storage condition tolerances are defined as the acceptable variations in temperature and relative humidity of storage facilities for stability studies. The equipment used should be capable of controlling the storage conditions within the ranges defined in these guidelines. The storage conditions should be monitored and recorded. Short-term environmental changes due to opening the doors of the storage facility are accepted as unavoidable. The effect of excursions due to equipment failure should be assessed, addressed and reported if judged to affect stability results.

Data from the accelerated storage condition and, if appropriate, from the intermediate storage condition can be used to evaluate the effect of short term excursions outside the label storage conditions (such as might occur during shipping). Long-term, accelerated and, where appropriate, intermediate storage conditions for APIs are detailed in sections 2.1.7.1–2.1.7.3. The general case applies if the API is not specifically covered by a subsequent section. Alternative storage conditions can be used if justified. If long-term studies are conducted at 25 °C ± 2 °C/60% RH ± 5% RH and “significant change” occurs at any time during six months’ testing at the accelerated storage condition, additional testing at the intermediate storage condition should be conducted and evaluated against significant change criteria. In this case, testing at the intermediate storage condition should include all long-term tests, unless otherwise justified, and the initial application should include a minimum of six months’ data from a 12-month study at the intermediate storage condition.^16,17

Table 4: Active Pharmaceutical Ingredients Intended for Storage in A Refrigerator

Study

Storage condition

Minimum time period covered by data at submission

Long-term

5 °C ± 3 °C

12 months

Accelerated^a

25 °C ± 2 °C/60% RH ± 5% RH or

30 °C ± 2 °C/65% RH ± 5% RH or

30 °C ± 2 °C/75% RH ± 5% RH

6 months

a. Whether accelerated stability studies are performed at 25 ± 2 °C/60% RH ± 5% RH or 30 °C ± 2 °C/65% RH ± 5% RH or 30 °C ± 2 °C/75% RH ± 5% RH is based on a risk-based evaluation. Testing at a more severe long term condition can be an alternative to storage testing at 25 °C/60%RH or 30 °C/65%RH.

Data on refrigerated storage should be assessed according to the evaluation section of these guidelines, except where explicitly noted below. If significant change occurs between three and six months’ testing at the accelerated storage condition, the proposed re-test period should be based on the data available at the long-term storage condition. If significant change occurs within the first three months’ testing at the accelerated storage condition a discussion should be provided to address the effect of short-term excursions outside the label storage condition, e.g. during shipping or handling. This discussion can be supported, if appropriate, by further testing on a single batch of the API for a period shorter than three months but with more frequent testing than usual. It is considered unnecessary to continue to test an API for the whole six months when a significant change has occurred within the first three months.¹⁷

Table 5: Active pharmaceutical ingredients intended for storage in a freezer

Study	Storage condition	Minimum time period covered by data at submission
Long-term	-20 °C ± 5 °C	12 months

In the rare case of any API of non-biological origin being intended for storage in a freezer, the re-test period or shelf-life should be based on the long-term data obtained at the long-term storage condition. In the absence of an accelerated storage condition for APIs intended to be stored in a freezer, testing on a single batch at an elevated temperature (e.g. 5 °C ± 3 °C or 25 °C ± 2 °C or 30 °C ± 2 °C) for an appropriate time period should be conducted to address the effect of short-term excursions outside the proposed label storage condition, e.g. during shipping or handling.¹⁸

Active pharmaceutical ingredients intended for storage below -20°C

APIs intended for storage below -20 °C should be treated on a case-by-case basis.

3.3.4 Stability commitment:

When the available long-term stability data on primary batches do not cover the proposed re-test period granted at the time of approval, a commitment should be made to continue the stability studies post-approval in order to firmly establish the re-test period or shelf-life. Where the submission includes long-term stability data on the number of production batches covering the proposed re-test period, a post-approval commitment is considered unnecessary. Otherwise one of the following commitments should be made:

If the submission does not include stability data on production batches, a commitment should be made to place the first two or three production batches on long-term stability studies through the proposed re-test period. The stability protocol used for long-term studies for the stability commitment should be the same as that for the primary batches, unless otherwise scientifically justified.¹⁸

3.3.5 Evaluation:

The purpose of the stability study is to establish, based on testing a minimum of the number of batches, unless otherwise justified and authorized, of the API and evaluating the stability information (including, as appropriate, results of the physical, chemical, biological and microbiological tests), a re-test period applicable to all future batches of the API manufactured under similar circumstances. The degree of variability of individual batches affects the confidence that a future production batch will remain within specification throughout the assigned re-test period. An approach for analysing the data on a quantitative attribute that is expected to change with time is to determine the time at which the 95% one-sided confidence limit for the mean curve intersects the acceptance criterion. If analysis shows that the batch-to-batch variability is small, it is advantageous to combine the data into one overall estimate. This can be done by first applying appropriate statistical tests (e.g. p values for level of significance of rejection of more than 0.25) to the slopes of the regression lines and zero time intercepts for the individual batches. If it is inappropriate to combine data from several batches, the overall re-test period should be based on the minimum time a batch can be expected to remain within acceptance criteria.¹⁹

This justification should be based on what is known about the mechanism of degradation, the results of testing under accelerated conditions, the goodness of fit of any mathematical model, batch size and existence of supporting stability data. However, this extrapolation assumes that the same degradation relationship will continue to apply beyond the observed data.

Any evaluation should cover not only the assay but also the levels of `degradation products and other appropriate attributes. Where appropriate, attention should be paid to reviewing the adequacy of evaluation linked to FPP stability and degradation “behaviour” during the testing.¹⁹

3.3.6 Statements and labelling:

A storage statement should be established for display on the label based on the stability evaluation of the API. Where applicable specific instructions should be provided, particularly for APIs that cannot tolerate freezing or excursions in temperature. Terms such as ambient conditions” or “room temperature” should be avoided. A re-test period should be derived from the stability information, and a retest date should be displayed on the container label if appropriate.^19,20

3.3.7 Ongoing stability studies:

The stability of the API should be monitored according to a continuous and appropriate programme that will permit the detection of any stability issue (e.g. changes in levels of degradation products). The purpose of the ongoing stability programme is to monitor the API and to determine that the API remains, and can be expected to remain, within specifications under the storage conditions indicated on the label, within the re-test period in all future batches. The ongoing stability programme should be described in a written protocol and the results presented in a formal report. The protocol for an ongoing stability programme should extend to the end of the re-test period and shelf-life and should include, but not be limited to, the following parameters:

— number of batch(es) and different batch sizes, if applicable;

— relevant physical, chemical, microbiological and biological test methods;

— acceptance criteria;

— reference to test methods;

— description of the container closure system(s);

— testing frequency;

description of the conditions of storage (standardized conditions for long-term testing as described in these guidelines, and consistent with the API labelling, should be used); and other applicable parameters specific to the API. 96

At least one production batch per year of API (unless none is produced during that year) should be added to the stability monitoring programme and tested at least annually to confirm the stability. In certain situations additional batches should be included in the ongoing stability programme. For example, an ongoing stability study should be conducted after any significant change or significant deviation to the synthetic route, process or container closure system which may have an impact upon the stability of the API.⁸

Out-of-specification results or significant atypical trends should be investigated. Any confirmed significant change, out-of-specification result, or significant atypical trend should be reported immediately to the relevant finished product manufacturer. The possible impact on batches on the market should be considered in consultation with the relevant finished product manufacturers and the competent authorities. A summary of all the data generated, including any interim conclusions on the programme, should be written and maintained. This summary should be subjected to periodic review.¹⁹

4. Stability Testing of Finished Pharmaceutical Product :^20,21

4.1 General:

The design of the stability studies for the FPP should be based on knowledge of the behaviour and properties of the API, information from stability studies on the API and on experience gained from preformulation studies and investigational FPPs.

4.2 Selection of batches:

Data from stability studies should be provided on at least three primar batches of the FPP. The primary batches should be of the same formulation and packaged in the same container closure system as proposed for marketing. The manufacturing process used for primary batches should simulate that to be applied to production batches and should provide product of the same quality and meeting the same specifi cation as that intended for marketing. In the case of conventional dosage forms with APIs that are known to be stable, data from at least two primary batches should be provided. Two of the three batches should be at least pilot-scale batches and the third one can be smaller, if justifi ed. Where possible, batches of the FPP should be manufactured using different batches of the API(s).²⁰

Stability studies should be performed on each individual strength, dosage form and container type and size of the FPP unless bracketing or matrixing is applied.

4.3 Container closure system:

Stability testing should be conducted on the dosage form packaged in the container closure system proposed for marketing. Any available studies carried out on the FPP outside its immediate container or in other packaging materials can form a useful part of the stress testing of the dosage form or can be considered as supporting information, respectively.

4.4 Specification:

Stability studies should include testing of those attributes of the FPP that are susceptible to change during storage and are likely to influence quality, safety, and/or effi cacy. The testing should cover, as appropriate, the physical, chemical, biological and microbiological attributes, preservative content (e.g. antioxidant or antimicrobial preservative) and functionality tests (e.g. for a dose delivery system).

Analytical procedures should be fully validated and stability-indicating. Whether and to what extent replication should be performed will depend on the results of validation studies. Shelf-life acceptance criteria should be derived from consideration of all available stability information. It may be appropriate to have justifiable differences between the shelf-life and release acceptance criteria based on the stability evaluation and the changes observed on storage. Any differences between the release and shelf-life acceptance criteria for antimicrobial preservative content should be supported by a validated correlation of chemical content and preservative effectiveness demonstrated during development of the pharmaceutical product with the product in its final formulation (except for preservative concentration) intended for marketing. A single primary stability batch of the FPP should be tested for effectiveness of the antimicrobial preservative (in addition to preservative content) at the proposed shelf-life for verification purposes, regardless of whether there is a difference between the release and shelf-life acceptance criteria for preservative content.²¹

4.4 Testing frequency:

For long-term studies, frequency of testing should be sufficient to establish the stability profile of the FPP. For products with a proposed shelf-life of at least 12 months, the frequency of testing at the long-term storage condition should normally be every three months over the first year, every six months over the second year and annually thereafter throughout the proposed shelf-life. At the accelerated storage condition, a minimum of three time points, including the initial and final time points (e.g. 0, 3 and 6 months), from a six-month study is recommended. Where an expectation (based on 98 development experience) exists that results from accelerated testing are likely to approach significant change criteria, testing should be increased either by adding samples at the final time point or by including a fourth time point in the study design. When testing at the intermediate storage condition is called for as a result of significant change at the accelerated storage condition, a minimum of four time points, including the initial and final time points (e.g. 0, 6, 9 and 12 months), from a 12-month study is recommended. Reduced designs, i.e. matrixing or bracketing, where the testing frequency is reduced or certain factor combinations are not tested at all, can be applied if justified.⁹

4.5 Storage conditions:

In general an FPP should be evaluated under storage conditions with specified tolerances that test its thermal stability and, if applicable, its sensitivity to moisture or potential for solvent loss. The storage conditions and the lengths of studies chosen should be sufficient to cover storage, shipment and subsequent use with due regard to the climatic conditions in which the product is intended to be marketed. Photostability testing, which is an integral part of stress testing, should be conducted on at least one primary batch of the FPP if appropriate. More details can be found in other guidelines. The orientation of the product during storage, i.e. upright versus inverted, may need to be included in a protocol where contact of the product with the closure system may be expected to affect the stability of the products contained, or where there has been a change in the container closure system. Storage condition tolerances are usually defined as the acceptable variations in temperature and relative humidity of storage facilities for stability studies. The equipment used should be capable of controlling the storage conditions within the ranges defined in these guidelines.²²

The storage conditions should be monitored and recorded. Short-term environmental changes due to opening of the doors of the storage facility are accepted as unavoidable. The effect of excursions due to equipment failure should be assessed, addressed and reported if judged to affect stability results. Excursions that exceed the defined tolerances for more than 24 hours should be described in the study report and their effects assessed.

The long-term testing should cover a minimum of six or 12 months at the time of submission and should be continued for a period of time sufficient to cover the proposed shelf-life. For an FPP containing an API that is known to be stable and where no significant change is observed in the FPP stability studies at accelerated and long-term conditions for at least 6 months data covering a minimum of six months should be submitted. Additional data accumulated during the assessment period of the registration application should be submitted to the authorities if requested. Data from the accelerated storage condition and from the intermediate conditions, where appropriate, can be used to evaluate the effect of short-term excursions outside the label storage conditions (such as might occur during shipping). Long-term, accelerated and, where appropriate, intermediate storage conditions for FPPs are detailed in the sections below. ^21,22

If long-term studies are conducted at 25 °C ± 2 °C/60% RH ± 5% RH and “significant change” occurs at any time during six months’ testing at the accelerated storage condition, additional testing at the intermediate storage condition should be conducted and evaluated against significant change criteria. In this case the initial application should include a minimum of six months’ data from a 12-month study at the intermediate storage condition.

In general “significant change” for an FPP is defined as:

A change from the initial content of API(s) of 5% or more detected by assay, or failure to meet the acceptance criteria for potency when using biological or immunological procedures. (Note: Other values may be applied, if justified, to certain products, such as multivitamins and herbal preparations.)

Any degradation product exceeding its acceptance criterion.

Failure to meet the acceptance criteria for appearance, physical attributes and functionality test (e.g. colour, phase separation, resuspendability, caking, hardness, dose delivery per actuation). However, some changes in physical attributes (e.g. softening of suppositories, melting of creams, partial loss of adhesion for transdermal products) may be expected under accelerated conditions. Also, as appropriate for the dosage form:

Failure to meet the acceptance criterion for pH; or Failure to meet the acceptance criteria for dissolution for 12 dosage units.²³

4.6.1 FPPs packaged in impermeable containers:

Parameters required to classify the packaging materials as permeable or impermeable depend on the characteristics of the packaging material, such as thickness and permeability coefficient. The suitability of the packaging material used for a particular product is determined by its product characteristics. Containers generally considered to be moisture impermeable include glass ampoules. Sensitivity to moisture or potential for solvent loss is not a concern for FPPs packaged in impermeable containers that provide a permanent barrier to passage of moisture or solvent. Thus stability studies for products stored in impermeable containers can be conducted under any controlled or ambient relative humidity condition.^23,24

4.6.2 FPPs packaged in semi-permeable containers:

Aqueous-based products packaged in semi-permeable containers should be evaluated for potential water loss in addition to physical, chemical, biological and microbiological stability. This evaluation can be carried out under conditions of low relative humidity, as discussed below. Ultimately it should be demonstrated that aqueous-based FPPs stored in semi-permeable containers could withstand environments with low relative humidity. Other comparable approaches can be developed and reported for nonaqueous, solvent-based products.

Table 7

Study	Storage condition	Minimum time period covered by data at submission
Long-term^a	25 °C ± 2 °C/40% RH ± 5% RH or 30 °C ± 2 °C/35% RH ± 5% RH	12 months
Intermediate	30 °C ± 2 °C/65% RH ± 5% RH	6 months
Accelerated	40 °C ± 2 °C/not more than (NMT) 25% RH	6 months

a. Whether long-term stability studies are performed at 25 °C ± 2 °C/40% RH ± 5% RH or 30 °C ± 2 °C/35% RH ± 5% RH is determined by the climatic condition under which the FPP is intended to be marketed. Testing at 30 °C/35% RH can be an alternative to the storage condition at 25 °C/40% RH.

Products meeting either of the long-term storage conditions and the accelerated conditions, as specified in the table above, have demonstrated the integrity of the packaging in semi-permeable containers. A significant change in water loss alone at the accelerated storage condition does not necessitate testing at the intermediate storage condition. However, data should be provided to demonstrate that the pharmaceutical product would not have significant water loss throughout the proposed shelf-life if stored at 25 °C/40% RH or 30 °C/35% RH.

For long-term studies conducted at 25 °C ± 2 °C/40% RH ± 5% RH, that fail the accelerated testing with regard to water loss and any other parameters, additional testing at the intermediate” storage condition should be performed as described under the general case to evaluate the temperature effect at 30 °C.^24,25

A 5% loss in water from its initial value is considered a significant change for a product packaged in a semi-permeable container after an equivalent of three months’ storage at 40 °C not more than (NMT) 25% RH. However, for small containers (1 ml or less) or unit-dose products, a water loss of 5% or more after an equivalent of three months’ storage at 40 °C/NMT 25% RH may be appropriate, if justified.

Example of an approach for determining water loss:

For a product in a given container closure system, container size and fill, an appropriate approach for deriving the rate of water loss at the low relative humidity is to multiply the rate of water loss measured at an alternative relative humidity at the same temperature, by a water loss rate ratio shown in the table below. A linear water loss rate at the alternative relative humidity over the storage period should be demonstrated. For example, at a given temperature, e.g. 40 °C, the calculated rate of water loss during storage at NMT 25% RH is the rate of water loss measured at 75% RH multiplied by 3.0, the corresponding water loss rate ratio.²⁶

Table 8

Low-humidity testing conditions	Alternative testing condition	Ratio of water loss rates	Calculation
25 °C/40% RH	25 °C/60% RH	1.5	(100-40)/ (100-60)
30 °C/35% RH	30 °C/65% RH	1.9	(100-35)/ (100-65)
30 °C/35% RH	30 °C/75% RH	2.6	(100-35)/ (100-75)
40°C/NMT 25% RH	40 °C/75% RH	3.0	(100-25)/ (100-75)

Valid water loss rate ratios at relative humidity conditions other than those shown in the table above can also be used.

Table 9: FPPs intended for storage in a refrigerator

Study

Storage condition

Minimum time period covered by data at submission

Long-term

5 °C ± 3 °C 12

12 months

Accelerated^a

25 °C ± 2 °C/60% RH ± 5% RH or

30 °C ± 2 °C/65% RH ± 5% RH or

30 °C ± 2 °C/75% RH ± 5% RH

6 months

a. Whether accelerated stability studies are performed at 25 ± 2 °C/60% RH ± 5% RH or 30 °C ± 2 °C/65% RH ± 5% RH or 30 °C ± 2 °C/75% RH ± 5% RH is based on a risk-based evaluation. Testing at a more severe accelerated condition can be an alternative to the storage condition at 25 °C/60% RH or 30 °C/65% RH.

If the FPP is packaged in a semi-permeable container, appropriate information should be provided to assess the extent of water loss. Data from refrigerated storage should be assessed according to the evaluation section of these guidelines, except where explicitly noted below.

If significant change occurs between three and six months testing at the accelerated storage condition, the proposed shelf-life should be based on the data available from the long-term storage condition.²⁷

Table 10: Fpps Intended for Storage in A Freezer

Study

Storage condition

Minimum time period covered by data at submission

Long-term

–20 °C ± 5 °C

12 months

For FPPs intended for storage in a freezer, the shelf-life should be based on the long-term data obtained at the long-term storage condition. In the absence of an accelerated storage condition for FPPs intended to be stored in a freezer, testing on a single batch at an elevated temperature (e.g. 5 °C ± 3 °C or 25 °C ± 2 °C or 30 °C ± 2 °C) for an appropriate time period should be conducted to address the effect of short-term excursions outside the proposed label storage condition.

FPPs intended for storage below -20 °C

FPPs intended for storage at temperatures below -20 °C should be treated on a case-by-case basis.²⁸

4.6 Stability commitment:

When the available long-term stability data on primary batches do not cover the proposed shelf-life granted at the time of approval, a commitment should be made to continue the stability studies post-approval to firmly establish the shelf-life. Where the submission includes long-term stability data from the production batches as specified in section 2.2.2 covering the proposed shelf-life, a post approval commitment is considered unnecessary. Otherwise, one of the following commitments should be made:

If the submission includes data from stability studies on at least the number of production batches, a commitment should be made to continue the long-term studies throughout the proposed shelf life and the accelerated studies for six months.

If the submission includes data from stability studies on fewer than the number of production batches, a commitment should be made to continue the long-term studies throughout the proposed shelf-life and the accelerated studies for six months, and to place additional production batches, to a total of at least three, on long-term stability studies throughout the proposed shelf-life and on accelerated studies for six months.²⁹

If the submission does not include stability data on production batches, a commitment should be made to place the fi rst two or three production batches on long-term stability studies throughout the proposed shelf-life and on accelerated studies for six months. The stability protocol used for studies on commitment batches should be the same as that for the primary batches, unless otherwise scientifically justified.³⁰

4.7 Evaluation: ^31,32

A systematic approach should be adopted to the presentation and evaluation of the stability information, which should include, as appropriate, results from the physical, chemical, biological and microbiological tests, including particular attributes of the dosage form (for example, dissolution rate for solid oral dosage forms). The purpose of the stability study is to establish, based on testing a minimum number of batches of the FPP as specified in section 2.2.2, a shelf-life and label storage instructions applicable to all future batches of the FPP manufactured under similar circumstances. The degree of variability of individual batches affects the confidence that a future production batch will remain within specification throughout its shelf-life. Where the data show so little degradation and so little variability that it is apparent from looking at the data that the requested shelf-life will be granted, it is normally unnecessary to go through the statistical analysis. However, a provisional shelf-life of 24 months may be established provided the following conditions are satisfied:³¹

The API is known to be stable (not easily degradable).

Supporting data indicate that similar formulations have been assigned a shelf-life of 24 months or more.

An approach for analysing the data on a quantitative attribute that is expected to change with time is to determine the time at which the 95% one-sided confidence limit for the mean curve intersects the acceptance criterion. If analysis shows that the batch-to-batch variability is small, it is advantageous to combine the data into one overall estimate. This can be done by first applying appropriate statistical tests (e.g. p values for level of significance of rejection of more than 0.25) to the slopes of the regression lines and zero time intercepts for the individual batches. If it is inappropriate to combine data from several batches, the overall shelf-life should be based on the minimum time a batch can be expected to remain within acceptance criteria. The nature of any degradation relationship will determine whether the data should be transformed for linear regression analysis. Usually the 105 relationship can be represented by a linear, quadratic or cubic function on an arithmetic or logarithmic scale. As far as possible, the choice of model should be justified by a physical and/or chemical rationale and should also take into account the amount of available data (parsimony principle to ensure a robust prediction).^32,33

Statistical methods should be employed to test the goodness of fit of the data on all batches and combined batches (where appropriate) to the assumed degradation line or curve.

Any evaluation should consider not only the assay but also the degradation products and other appropriate attributes. Where appropriate, attention should be paid to reviewing the adequacy of evaluation linked to FPP stability and degradation “behaviour” during the testing.³⁴

4.8 Statements and labelling:

A storage statement should be established for the label based on the stability evaluation of the FPP. Where applicable, specific instructions should be provided, particularly for FPPs that cannot tolerate freezing. Terms such as “ambient conditions” or “room temperature” must be avoided. There should be a direct link between the storage statement on the label and the demonstrated stability of the FPP. An expiry date should be displayed on the container label.³⁵

4.9 In-use stability:

The purpose of in-use stability testing is to provide information for the labelling on the preparation, storage conditions and utilization period of 106 multidose products after opening, reconstitution or dilution of a solution, e.g. an antibiotic injection supplied as a powder for reconstitution.

As far as possible the test should be designed to simulate the use of the FPP in practice, taking into consideration the filling volume of the container and any dilution or reconstitution before use. At intervals comparable to those which occur in practice appropriate quantities should be removed by the withdrawal methods normally used and described in the product literature. The physical, chemical and microbial properties of the FPP susceptible to change during storage should be determined over the period of the proposed in-use shelf-life. If possible, testing should be performed at intermediate time points and at the end of the proposed in-use shelf-life on the fi nal amount of the FPP remaining in the container. Specific parameters, e.g. for liquids and semi-solids, preservatives, per content and effectiveness, need to be studied. A minimum of two batches, at least pilot-scale batches, should be subjected to the test. At least one of these batches should be chosen towards the end of its shelf-life. If such results are not available, one batch should be tested at the final point of the submitted stability studies.^35,36

This testing should be performed on the reconstituted or diluted FPP throughout the proposed in-use period on primary batches as part of the stability studies at the initial and final time points and, if full shelf-life, long-term data are not available before submission, at 12 months or the last time point at which data will be available. In general this testing need not be repeated on commitment batches.

4.11 Variations:

Once the FPP has been registered, additional stability studies are required whenever variations that may affect the stability of the API or FPP are made, such as major variations.

The following are examples of such changes:

— Change in the manufacturing process;

— Change in the composition of the FPP;

— Change of the immediate packaging;

— Change in the manufacturing process of an API.

In all cases of variations, the applicant should investigate whether the intended change will or will not have an impact on the quality characteristics of APIs and/or FPPs and consequently on their stability. The scope and design of the stability studies for variations and changes are based on the knowledge and experience acquired on APIs and FPPs. The results of these stability studies should be communicated to the regulatory authorities concerned.³⁷

5. CONCLUSION:

Stability testing of small molecule API’s and finished products is at a mature level of development. The requirements of the regulatory authorities, the scientific principles and techniques for accumulating, analysing and presenting the data is well understood and documented in the ICH guidelines. With every advancement in the production and manufacture of biopharmaceuticals additional knowledge and understanding is gained; however, the goalposts are also changing and the requirements of the regulators and the mechanisms of meeting these needs are under constant review.

As we have noted the basic principle behind stability testing has not changed; however, the inherent variability and difficulties in manufacturing biopharmaceuticals is making effective stability testing an increasing difficult art. 2005 saw a record year for approvals of biopharmaceuticals within the FDA with 21 products receiving official FDA approval. However, in the subsequent years there has been a slow down in approvals.

There are a number of reasons behind this and the inference is not that this is linked to stability testing failure but it is indicative that the regulatory requirements for a biopharmaceutical are evolving and that success of a biopharmaceutical can be enhanced through constant and continued dialogue coupled with a full understanding of the process, the product and the variability that lies within.

Permanent improvements of quality control protocols on a global platform requires flexible and easy to adjust climatic cabinets. The withdrawal of Q1F and the introduction of ASEAN ICH guidelines is a clear indication that changes to improve the quality assurance for stability testing are present. Current discussion to consider temperature changes (cyclic testing of pharmaceuticals), the introduction of country (region) specific stress tests and the tightening of limits are possible adaptations in the future.

It remains to follow - with some tension - how quick changes will be implemented. However, it is certain that higher demands are being placed on stability testing and high-performance systems which meet demands today and in the future are needed. Therefore users should consider the choice of product for their stability testing an investment in high performance is offering a far better degree of security and future adaptations today.

6. REFERENCES:

1. ICH Q1A(R2). Stability testing guidelines: Stability testing of new drug substances and products. ICH Steering Committee, 2003:1-23.

2. Panda A, Kulkarni S., Tiwari R. Stability Studies: An Integral Part of Drug Development Process. International Journal of Pharmaceutical Research and Bio-Science, 2013;2;69-80.

3. Valerie Sautou, Methodological Guidelines for Stability Studies of Hospital Pharmaceutical Preparations, Part 1: Liquid preparation. October 2013,9-16.

4. Rao G., Goyal A., Development of Stability Indicating Studies for Pharmaceutical Products: An Innovative Step, International Journal of Pharmaceutical Chemistry and Analysis, 2016;3:110-116.

5. WHO. Stability studies in a global environment. Geneva meeting working document QAS/05.146 with comments, 2004.

6. Cha J, Gilmor T, Lane P, Ranweiler JS. Stability studies in Handbook of Modern Pharmaceutical Analysis. Separation Science and Technology. Elsevier, 2001;459-505.

7. Kommanaboyina B, Rhodes CT. Trends in stability Testing, with Emphasis on Stability During Distribution and Storage. Drug Development and Industrial Pharmacy. 1999;25:857-867.

8. Anderson G, Scott M. Determination of product shelf life and activation energy for five drugs of abuse. Clinical Chemistry. 1991;37:398-402.

9. Connors KA, Amidon GL, Kennon L. Chemical Stability of Pharmaceuticals-A Handbook for Pharmacists. John Wiley and Sons, New York: 1973;8-119.

10. Lachman L, Lieberman H. Kinetic principles and stability testing. The Theory and Practice of Industrial Pharmacy. CBS Publishers and Distributors Pvt Ltd, New Delhi, Fourth Edition 2013:1036-1072.

11. Bott RF, Oliveira WP. Storage conditions for stability testing of pharmaceuticals in hot and humid regions. Drug Development and Industrial Pharmacy. 2007;33:393-401.

12. International Conference on Harmonisation. ICH Q6A: Specifi cations: Test procedures and acceptance criteria for new drug substances and new drug products: Chemical substances (http://www.ich.org/LOB/media/ MEDIA430.pdf).

13. Thorat P, Warad S, Solunke R, Sargar A, Bhujbal A, Shinde A. Stability Study of Dosage Form: An Inovative Step, World Journal of Pharmacy and Pharmaceutical Sciences, 2014;3:1031-1050.

14. Bajaj S, Singla D, Sakhuja N. Stability Testing of Pharmaceutical Products. Journal of Applied Pharmaceutical Science. 2012;2:129-138.

15. Singh S., Bakshi M. Guidance on conduct of stress test to determine inherent stability of drugs. Pharmaceutical Technology Asia, Special Issue, Sep. /Oct. 2000;24-36.

16. Grimm W. Extension of the international conference on harmonization tripartite guideline for stability testing of new drug substances and products to countries of climatic zones 3 and 4. Drug Development and Industrial Pharmacy. 1998;24:313-325.

17. Ali J, Khar RK, Ahuja A. Dosage form and Design. Birla Publications Pvt. Ltd: Delhi,2008;100-123.

18. Cha J, Gilmor T, Lane P, Ranweiler JS. Stability studies in Handbook of Modern Pharmaceutical Analysis. Separation Science and Technology. Elsevier, 2001;459-505.

19. Guidance on variations to a prequalifi ed product dossier. In: WHO Expert Committee on Specifi cations for Pharmaceutical Preparations. Forty-fi rst report. Geneva, World Health Organization, 2007, Annex 6 (WHO Technical Report Series, No. 943).

20. International Conference on Harmonisation. ICH Q1A (R2): Stability testing of new drug substances and products. (http://www.ich.org/LOB/media/ MEDIA419.pdf).

21. Prequalifi cation Programme – Priority Essential Medicines. A United Nations Programme managed by WHO. Information for applicants (http://mednet3.who. int/prequal/).

22. Guidelines for stability testing of pharmaceutical products containing well established drug substances in conventional dosage forms. In: WHO Expert Committee on Specifications for Pharmaceutical Preparations. Thirty-fourth report. Geneva, World Health Organization, 1996, Annex 5 (WHO Technical Report Series, No. 863).

23. Pokharana M, Vaishnav R, Goyal A, Shrivastava A. Stability testing guidelines of pharmaceutical products. Journal of Drug Delivery and Therapeutics. 2018 Mar 15;8(2):169-75.

24. Regional Guidelines on stability testing of active substances and pharmaceutical products for the WHO Eastern Mediterranean Region. August 2006. (http://www.emro.who.int/edb/media/pdf/EMRC5312En.pdf).

25. Further information can be found on the ICH homepage:http://www.ich.org/cache/ compo/276-254-1.html.

26. Guidelines on active pharmaceutical ingredient master fi le procedure. In: WHO Expert Committee on Specifi cations for Pharmaceutical Preparations.

27. Forty-second report. Geneva, World Health Organization, 2008, Annex 4 (WHO Technical Report Series, No. 948).

28. WHO guidelines for stability evaluation of vaccines. In: WHO Expert

29. Committee on Biological Standardization. Fifty-seventh report. Geneva, World Health Organization (WHO Technical Report Series, (in press))

30. (http://www.who.int/biologicals/publications/trs/areas/vaccines/stability/en/ index.html).

31. Schumacher P. 1972. Über eine für die Haltbarkeit von Arzneimitteln maßgebliche Klimaeinteilung [The impact of climate classifi cation on the stability of medicines]. Die Pharmazeutische Industrie, 34:481–483.

32. Grimm W. 1986. Storage conditions for stability testing (Part 2). Drugs Made in Germany, 29:39–47.

33. Grimm W. 1998. Extension of the International Conference on Harmonisation Tripartite Guidelines for stability testing of new drug substances and products to countries of Climatic Zones III and IV. Drug Development and Industrial Pharmacy, 24:313-325.

34. Zahn M. et al. 2006. A risk-based approach to establish stability testing conditions for tropical countries. Journal of Pharmaceutical Sciences, 95:946–965. Erratum: Journal of Pharmaceutical Sciences, 2007, 96:2177.

35. WHO good manufacturing practices: main principles for pharmaceutical products. In: Quality assurance of pharmaceuticals. A compendium of guidelines and related materials. Volume 2, 2nd updated edition. Good manufacturing practices and inspection. Geneva, World Health Organization, 2007, Chapter 1.

36. Asean Guideline on stability study of drug product, 9th ACCSQ-PPWG Meeting, Philippines, 21–24 February 2005, version 22 February 2005.

37. Accelerated stability studies of widely used pharmaceutical substances under simulated tropical conditions. Geneva, World Health Organization, 1986 (WHO/PHARM/86.529).

Received on 15.07.2021 Modified on 19.08.2021

Res. J. Pharma. Dosage Forms and Tech.2021; 13(4):317-328.

DOI: 10.52711/0975-4377.2021.00052

A review of the current ICH Guidelines establishes that there are six documents which are specific in their application to the stability testing of pharmaceutical products and components both small molecule and biopharmaceutical.12

2.2. WHO Guidelines:

A review of the current ICH Guidelines establishes that there are six documents which are specific in their application to the stability testing of pharmaceutical products and components both small molecule and biopharmaceutical.¹²