1. INTRODUCTION:

1.1 Quality by design (QbD):

Qualitybydesign (QbD) has become a main standard in the pharmaceutical industry since it was introduced by the US Food and Drug Administration (USFDA). For any entity, quality is one of the basic criteria in addition to safety and efficacy to be accepted and approved as a drug.

The quality is the suitability of either a drug substance or a drug product for its intended use. According to ICH Q8 guidelines, QbD can be defined as “A Systematic approach for development that begins with predefined objectives and emphasizes the product and process understanding as well as process control, based on sound science and quality risk management. The formation of a design place by the QbD approach resolving a suitable method control that delivers its intended area and also eliminates batch failure increases efficiency and cost-effectiveness^.1,2,3

Table: 1 Historical Background of QbD:⁴

YEAR	ACTIVITIES
1950	Operation windows
1970	QbD created by Joseph M Juran
Sept 2002	QbD concept integrated by USFDA in cGMP
Sept 2004	USFDA releases final report in “pharmaceutical cGMP”
Sept 2004	USFDA guidelines for industry: PART-A framework for innovative pharmaceutical development, manufacturing, and quality assurance
Sept 2004	ICH: Q8(R2) pharmaceutical development
Nov 2005	ICH: Q9 quality risk management
June 2008	ICH: Q10 pharmaceutical quality system

Regulatory authorities are always proposing the implementation of ICH quality guidelines such as Q8, Q9, and Q10 and Q11. Guidelines associated with mathematical models are used for the understanding of the subject separately. Factors that affect the robustness are considered for the improvement of the analytical method in the QbD environment.⁵ The FDA has adopted Quality by Design (or QbD) principles in drug discovery, product development, and commercial manufacturing. QbD can be looked at as “a risk-based approach to manufacturing practices to ensure that your development and processes yield a quality product based on solid scientific and engineering principles”.This implies that regular design reviews focused on QbD be included as part of the project life cycle development model.^5,6,7

1.2. DEFINITION OF AQBD:

QbD principles when applied to the development of analytical methods are coined as “AQbD”. Analogous to process QbD, the outcome of AQbD is a well understood, fit for the purpose, and robust method that consistently delivers the intended performance throughout its lifecycle.⁸The AQbD can be used for the determination and development of a precise and cost reliable analytical method which is applied at any level the whole product lifecycle. The higher authorities have provided recent changes in the analytical method without revalidation of the AQbD approach that has been designing and implemented during the development of the analytical method.⁹

1.3. APPROACH TRADITIONAL APPROACH VS. ANALYTICAL QbD APPROACH:¹⁰

Traditional validation methods are usually a one-time evaluation. As a result changes in method failure during movement are always high. Also, the performance variable is not fully explored and knowledge. Therefore the below figure the comparison of traditional and AQbD approaches.

Table: 2 Traditional approaches vs. Analytical QbD approach

Traditional approach	Analytical QbD approach
Based empirical approach	Based on the systematic approach
Quality is assured by end samples testing	Robustness and reproducibility of the method build-in method improvement
Including the only date for submission	Submission with product understanding and assuring by analytical target profile
Specifications are based on batch history	Based on method achievement to ATP criteria
Process is frozen	Method flexibility with MODR and allowing continuous development
Focusing on reproducibility, ignoring variations	Focus on robust and loss effective method
Limited and simple	Replacing the need for revalidation and minimizing OOT and OOS

Table: 3 List of regulatory guidance or other QbD related activity¹²

Agency	Guidelines/Activities	Month (year)
USFDA	Pharmaceutical cGMP for the 21^st century –A risk-based approach: second progress report and implementation plan	Sep 2003
USFDA	Guidance for industry: PART-A framework for innovative pharmaceutical development, manufacturing, and quality assurance	Sep 2004
USFDA	Pharmaceutical cGMP for the 21^st century-A risk-based approach: final report	Sep 2004
EMA	The European medicines agency road map to 2010: preparing the ground for the future	March 2005
ICH	Pharmaceutical development (Q8)	Nov 2005
ICH	Quality risk management (Q9)	Nov 2005
ICH	Pharmaceutical quality system (Q10)	June 2008
ICH	Pharmaceutical development (Q8(R2))	Aug 2009
WHO	Quality risk management	Aug 2010
EMA	Road map to 2015	Dec 2010
USFDA	Guidance for industry: process validation: general principles and practices	Jan 2011
EMA-USFDA	EMA-FDA pilot program for parallel assessment of quality by design applications	March 2011
ICH	ICH- An endorsed guide for ICH Q8/Q9/Q10 Implementation	Dec 2011
EMA	ICH Quality IWG points to consider for ICH Q8/Q9/Q10 Guidelines	Feb 2012
EMA	Guidelines on real-time release testing (formerly guideline on parametric release)	March 2012
EMA	Guideline on process validation (draft)	March 2012
USFDA	Quality by design for ANDAs: an example for immediate- release dosage forms	April 2012
ICH	Development and manufacturing of drug substances (chemical entities and biotechnological/biological entities) (Q11)	May 2012
EMA- US- FDA	EMA- FDA pilot program for parallel assessment of quality-by-design application: lessons learned and QandA resulting from the first parallel assessment	Aug 2013
EMA	Guidelines on process validation for finished products – information and data to be provided in regulatory submission	Feb 2014

1.4 Regulatory guidelines analytical QbD:

Historically, designing or building the quality into products had been a necessity for complex manufacturing operations, like, aircraft manufacturing. However, in pharmaceutical development, it formally started with the release of a guidance document entitled ‘Pharmaceutical cGMP or the 21^st Century: A Risk-Based Approach’, by USFDA in August 2002. Since then, a lot has happened in the pharmaceutical QbD area resulting in the issue of multiple regulatory guidelines, which are listed in Table.¹¹

Analytical sciences are considered an integral part of pharmaceutical development. Analytical methods and product development go hand in hand during the entire life cycle of any pharmaceutical product. The traditional approach of analytical method development is quite tedious owing to a high degree of variability involved at each stage of method improvement.¹¹

2. Steps involved AQbD in implementation:

The application of quality by design concept to an analytical method is justified, because of many variables that significantly affect the method results. These variables are such as apparatus settings, sample characteristics, method parameters, and selection of calibration models. Being chromatographic method is the most common analytical tool in pharmaceutical quality control, and the number of variants involved in the analytical method development phase is almost equivalent to the number of variables involved in the formulation and development protocol for the dosage form. As per FDA, analytical techniques and methods play an essential role in the QbD paradigm, and real-time release testing and nontraditional testing techniques provide valuable information for in-process control and improvement. Implementation of QbD provides an opportunity to achieve regulatory flexibility but requires a high degree of robustness, product quality, and analytical method understanding.¹³

Figure: 1 AQbD tool

2.1 Analytical target profile (ATP):

Quality by design is a systematic approach to sample, process design, and development; therefore it begins with a determination of method goal or method intent. During this stress is given on the product and process understanding, ATP is a way for new method development. It is normally the goal of the chromatographic method is separation, qualification, and recognition of drug substance, impurity, or degradant. Impurity is taken into account to be the critical quality attributes (CQA). While dealing with traces of impurities it will be helpful to have an understanding of previous synthetic and manufacturing procedures and all alternative possible pathways and so on as delineated in the ICH guideline. As like conventional method, the QbD method additionally want detailed data information of analyte like its solubility, pKa, pH, UV chromophore, stability. Reinforce these data rigorous method goals as ATP can be set to obtain the best method. This provides a framework to method development that helps for further planning, ATP is in complete accordance with ICH guidelines. Therefore analytical target profile is the combination of all work criteria required for the intended analytical application that directs the method improvement procedure. An ATP associate degree ATP would develop for each of the attributes outlined in the management strategy. The ATP defines what the method has to measure and to what level the measurement is required (i.e. performance level characteristics, such as precision, accuracy, working range, sensitivity, and the associated performance criterion). Any method conforming to the ATP is considered suitable. The ATP will be regarded as the focal point in all stages of the analytical life cycle.⁴

2.2 Critical quality attributes (CQA):

ICH Q8 defines CQA or CPA as a physical, chemical, biological, or microbiological property or characteristic that should be within a proper limit, range, or distribution to ensure the desired product quality. CQA for the analytical method comprises method attributes and method parameters. CQA can differ from one analytical method to another. CQA for HPLC (UV or RID) is a kind of butter used in the mobile phase, pH of the mobile phase, diluents, column selection, organic modifier, and elution method. CQA for GC method is oven temperature and its program, injection temperature, a flow rate of gas, sample diluents, and concentration. CQA for HPTLC and TLC plate, mobile phases, injection concentration and volume, time is taken for plate development, a reagent for color improvement, and detection methods. Physical and chemical properties of the drug substance and impurities can also describe CQA for analytical method development such a polarity, charged functional groups, solubility, pH value, boiling point, and solution stability. Factors that directly affect the quality and safety of the sample are first sorted out, and its possible effect on method development is studied. Knowledge of the product and method will help to sort the CQA. If a drug product contains an impurity that may have a direct effect on the quality and safety of the drug product it is being considered the CQA for the HPLC method development of that particular drug compound. Safety and specification, intermediate specification, and procedure control efficacy can be achieved by demonstrating measurable control of quality attributes i.e. product.¹⁴

2.3 Risk Assessment:

Risk assessment strategy as specified in ICH Q9 guidelines. “It is a systematic process for assessment, control, communication and review of risks to the quality across the product lifecycle”. This step is vital to reach a confidence level that the method is reliable. Once the method is identified, AQbD emphasizes detailed risk assessment of the factors that may lead to possible variability in the method, like analyst methods, apparatus configuration, measurement and method parameter, sample characteristics, sample preparation, and environmental conditions. Traditional method development relied on testing the method after transfer whereas analytical QbD demands the risk assessment step before method transfer and throughout the product life cycle. According to ICH Q9, risk assessment can be carried out in three steps viz., risk identification, risk analysis, and risk evaluation. One of the common ways to perform risk assessment is to use a fishbone diagram, also known as Ishikawa. Accordingly, the risk factors are classified into the following categories:

a) High-risk factors: e.g. sample preparation methodology. These are to be fixed during the method improvement procedure.

b) Noise factors: these are subjected to an MSA study. It can be done through staggered cross-nested study design and variability plots, ANOVA, etc. these factors are subjected to robustness testing.

c) Experimental factors: e.g. instrumentation and operation methods. Subjected to ruggedness testing and acceptable range is identified. The third step is risk evaluation which is done through failure mode and effects analysis (FMEA) and the matrix designs. ⁶

(Risk assessment is the linkages between material attributes and process parameters. It is performed during the lifecycle of the product to identify the critical material attributes and critical process parameters.¹⁵

2.4 Method Operable Design Region (MODR):

MODR is a systematic series of experiments, in which purposeful changes are made to input factors to identify causes; for significant changes in the output responses and determining the relationship between factors and responses to evaluate all the potential factors simultaneously, systematically, and speedily. MODR permits flexibility in various input method parameters to provide the expected method performance criteria and method response without resubmission to FDA. Once this is defined, appropriate method controls can be put in place, and verification and method validation can be carried out.

2.4.1 Screening:

In screening, qualitative input variables can be screened out. It identifies the various critical method parameters (CMP) to be considered in the optimization experiments. When the goal is to screen numerous factors, fractional factorial design or Plackett Burman designs can be used. If the factors are more than four but less than six, then the fractional factorial design an optimized and when the factors are more than six then Plackett Burmann's design can be used.

2.4.2 Optimization:

For optimization, we can select, factorial designs, response surface, and mixture designs. When the goal is to evaluate the main effects and the interactions between the factors and the factors are more than 2 and less than five, then full factorial designs can be selected. When the goal is the optimization of known individual critical factors and the factors are limited to two to four, then response surface designs are selected. When the goal optimization of ratio of critical components in mixture and factors are component of a mixture, then mixture designs are selected.

2.4.3 Selection of model:

After all Experimental Runs, an analysis of the model (a mathematical relationship between factors and response), should be selected which depends on the shape of the expected response behavior. It could be linear, quadratic, cubic, Scheffer. It could be linear, quadratic, cubic, Scheffer. For Selection of Model, ANOVA should be carried out thoroughly for testing of significance of each Model with Lack of Fit and Goodness of Fit Statistics. In this, the f value, p-value, precision value, and R2 adjusted and predicted are to be studied.

2.4.4 Interpretation of model graphs:

Model Graphs will give a clear picture of how the response will behave at different levels of factors at a time through predicted response equation with individual coefficients which includes a) 1D interaction: it shows the linear effect of changing the level of a single factor. b) 2D contour: reveals the effect of 2 in dependant factors on one response at a time. C) 3D surface: it reveals the effect of and 4D cube. After Development of Design Space, a Minimum of 3 Confirmatory Experimental Runs should be conducted within a defined range of design space for Verification of the Design Space.¹

2.5 Control Strategy:

A planned set of controls, derived from current product and process for understanding that ensures procedure performance and also product quality. The control includes parameters and its attributes related to the drug substance and drug product materials and compounds, ability, and apparatus operating condition, in-process controls, finished- product specification, and the associated methods and frequency of monitoring and control. It is specifically, the control strategy may include: control of input material attributes (e.g. drug substance, excipients, primary packaging materials) based on an understanding of their impact on processability or product quality. It includes protection control, such as utilities, environmental systems, and operating conditions. There are control strategies that established the necessary control- based on patient requirement and it will be applied throughout the whole product lifecycle from product and procedure design through to a final product, including the API and drug product manufacture, packaging, and distribution. ⁽¹⁶⁾ The controls can include parameters and attributes related to drug substance and drug product materials and components, facility and equipment operating conditions, in-process controls, finished product specifications, and the associated methods and frequency of monitoring and control.¹⁷

2.6 Continues improvement:

Efforts have to be made so that product quality is improved throughout its life cycle. There are four specific pharmaceutical quality system elements to achieve this objective. The outcomes of exploratory and clinical improvement studies can be considered as useful inputs for product development. The knowledge gained from technology transfer activities provides useful inputs for manufacturing procedure, control strategy, and process validation which forms the backbone for continued product and process development. During commercial manufacturing, the pharmaceutical quality system should identify and evaluate the improvement opportunities. The understanding resulting from the commercial manufacturing should also be utilized for continual product improvement. Opportunities for innovative approaches to improve product quality should always be evaluated depending upon the particular stage of the product life cycle.¹⁸

3. STRESS TESTING:

It is important to have a clear deﬁnation of terms to facilitate the discussion. In the context of pharmaceuticals, ‘‘stress testing’’ is historically a somewhat vague and undeﬁned term, often used interchangeably with the term ‘‘accelerated stability.’’ A 1980 article by Pope deﬁned accelerated stability testing as ‘‘the validated method or methods by which product stability may be predicted by storage of the product under conditions that accelerate change in a deﬁned and predictable manner.’’²⁰ The International Conference on Harmonization (ICH) guideline entitled stability testing of new drug substances and products to require that stress testing be carried out to elucidate the inherent stability characteristics of the active substance.²¹

Stress testing is the main tool that is used to predict stability-related problems, develop analytical methods, and identify degradation products and pathways. Stability-related issues can affect many areas, including the following:

· Analytical methods development

· Formulation and package development

· Appropriate storage conditions and shelf-life determination

· Safety/toxicological concerns

· Manufacturing/processing parameters

· Absorption, distribution, metabolism, and excretion (ADME) studies

Environmental assessment it is worth discussing briery each of these stability-related areas.²²

Table 4: Design of experiment in AQbD¹⁹

Design	Number of variables and usage	Advantage	Disadvantage
Full factorial design (FFD)	Optimization and 2-5 variables	Identifying the main and interaction effect without any confounding.	Experimental runs increase with an increase in several different.
Fractional factorial design (FFD) or Taguchi methods	Development and screening different	Requiring a lower number of experimental runs	Determine cofounding effect of communication is a difficult job
Plackett-Burman method (PBD)	Screening /recognize vital one or more factors from a wide number of variables	Requiring very one/more runs for a large number of alternation.	It does not reveal communication effect
Pseudo-Monte Carlo sampling (pseudorandom sampling) method	Significant risk analysis or optimization	Behavior and variation to the model can be investigated with ease and speed.	For nonconvex design place, this method of sampling can be more complex to employ

3.1 Objective:

Following are some of the reasons to carry out the forced degradation studies:

· Stability related problems are solved by these studies.

· More stable formulations are generated by this study.

· The structure of degradation products is elucidated by these studies.

· Degradation pathways of drug substances and drug products are established by these studies.

· Stability indicating the nature of a developed method is established by these studies.

· Determination of the intrinsic stability of the drug substances in the formulation.

· Chemical characteristics of drug molecules are understood by these studies.

· Degradation mechanisms such as hydrolysis, oxidation, photolysis, or thermolysis of drug substance and drug product are understood by these studies.²³

3.2 Need for force degradation study:

Studies on forced degradation of drug molecules are very important in the following aspects.

· To develop methods to determine stability.

· To determine the degradation pathways.

· For determination of intrinsic stability of the drug in dosage forms.

· To study the chemical properties of molecules.

· For the production of stable formulations.

· To determine the structure of decomposition products.

· To solve problems related to stability.

· To generate a degradation profile under ICH conditions²⁴

3.3 Degradation condition of stress testing:

Hydrolysis, thermal, oxidation, and photodegradation are commonly used stress study mechanisms in the industry. The desired degradation level can be achieved by choosing a suitable concentration of acid, base, and oxidizing agent, applying combination stress (e.g., degradation media+ temperature) and exposure time. Excess degradation of a sample may lead to further degrade impurities and form secondary degradants that would not be seen in real-time stability studies. Excess degradation may mislead mass balance results also because of differences in response factors of unknown impurities. Not achieving the desired degradation might not serve the purpose of force degradation. The generally recommended degradation varies between 5-20% degradation.²⁵

3.3.1 Hydrolytic degradation:

Hydrolytic is a chemical process that combined decomposition of a chemical compound by reaction with water. Hydrolytic study's lower acidic and basic condition involves catalysis of ionizable functional groups present in the molecule. Acid or base stress testing requires forced degradation of drug substances by the exhibition to an acidic or basic condition which generates first degradants in a desirable range. The selection of the type and concentrations of acid or base depending on the stability of the drug substance. Hydrochloric acid or sulfuric acids (0.1-1 M) for acid hydrolysis and sodium hydroxide or potassium hydroxide (0.1-1 M) for base hydrolysis are advice as to suitable reagents for hydrolysis. Hydrolysis of most of the drugs depends upon the related concentration of hydronium and hydroxyl ions such as a) Anastrozole, significant degradation in basic condition products were formed lower basic pH, b) Doxofylline, a bronchodilator drug that shows degradation more in acidic condition.²⁶ Stress testing trial is normally started at room temperature and if there is no degradation, elevated temperature (50-70℃) is applied. Stress testing should not exceed more than 7 days. The degraded sample is then neutralized using acceptable acid, base/buffer, to avoid further decay.²⁷

3.3.2 Oxidative degradation:

Hydrogen peroxide is mostly used for oxidation of drug substances in forced degradation studies but some other oxidizing agents such as metal ions, oxygen, and radical initiators (azobisisobutyronitrile, AIBN) can be also used. Many drug substances experience auto-oxidation i.e. oxidation under normal storage condition and require ground state elemental oxygen. Therefore it is an important degradation pathway of many drugs. Auto-oxidation is a free radical reaction that requires a free radical initiator to begin the chain reaction. Hydrogen peroxide, metal ions, and trace levels of impurities in a drug substance act as initiators for the drug substance. The choice of an oxidizing agent, its concentration, and its condition depend on the drug substance. It communicates that the drug solutions are subjecting to 0.1%-3% hydrogen peroxide at neutral pH and room temperature for 7 days or up to a highest 20% degradation could potentially generate relevant degradation products. The mechanisms of oxidative degradation of drug substances require an electron transfer mechanism to form reactive anions and cations. Amines, sulfides, and phenols are susceptible to electron shifting oxidation to give N- oxides, hydroxylamine, sulphones, and sulphoxide. In some drugs, extensive degradation is seen when exposed to 3% of hydrogen peroxide for a very shorter period at room temperature. ^28,29

3.3.3 Thermal degradation:

Thermal degradation (e.g., dry and heat) should be carried out at more strenuous conditions than recommended ICH Q1A accelerated testing conditions. Samples of solid-state drug substances and drug products should be an exhibit to dry and wet heat, while liquid drug products should be uncovered to dry heat. Studies may be conducted at high temperatures for a short period. The effect of temperature on thermal degradation of a substance is studied through the Arrhenius equation:

K=Ae^-Ea/RT

Where k is a specific reaction rate, A is frequency factor, Ea is the energy of activation, R is gas constant (1.987 cal/deg mole) and T is the absolute temperature. A thermal degradation study is carried out at 40℃ to 80℃. ⁽²⁰⁾ the most generally accepted temperature is 70℃ at the lowest and highest humidity for 1-2 months. High temperature (>80℃) may not produce a predictive degradation pathway. The use of higher temperatures in predictive degradation studies assumes that the drug molecule will follow the same pathway of decay at all temperatures. This assumption may not hold for all drug molecules, and therefore important care must be taken in using the extreme temperatures quickly accessible in a sealed- vessel microwave trial for predictive studies.³⁰

3.3.4 Photolytic degradation:

In photolytic degradation studies, the drug substance is exposed to UV or florescent conditions. In this study, the drug substance or drug product (solid/liquid) is an exhibition to the light source according to the ICH Q1B protocol. The simple use of radiation range for degradation studies is about 300-800 nm. In photolytic conditions, the degradation occurs due to oxidation through a free radical mechanism or non-oxidation procedure involve with isomerization, dimerization, etc. On the other hand, oxidative photolytic reaction contains mechanisms involving singlet or triplet oxygen states. Singlet oxygen act with unsaturated compounds to produce photooxidative decay products, while triplet oxygen follows a free radical mechanism, to produce peroxide. Notably, it is shown that light also catalyzes oxidation reaction. In non-oxidative procedures, several types of reactions are observed such as the hemolytic breakage of C-X bonds, deamination, and cleavage of C-S bonds.³¹ Hence, light can also act as a catalyst for the oxidation reaction. Hence, the characterization of the photodegradation process involving the study of the transient species and the interaction between precursors and products is a crucial way to understand the potential phototoxicity of a drug and determining it.³²

Table 5: Stress condition: ⁽³³⁾

Degradation type	Experiment condition	Storage condition	Sampling time
Hydrolysis	Control API (no acid or base)	40℃, 60℃	1, 3, 5 days
	0.1 N NaOH	40℃, 60℃	1, 3, 5 days
	0.1 N NaOH	40℃, 60℃	1, 3, 5 days
	Acid control (no API)	40℃, 60℃	1, 3, 5 days
	Base control (no API)	40℃, 60℃	1, 3, 5 days
	pH: 2,4,6,8	40℃, 60℃	1, 3, 5 days
Oxidative	3% H₂O₂	25℃, 40℃	1, 3, 5 days
	Peroxide control	25℃, 40℃	1, 3, 5 days
	Azobisisobutyronitrile (AIBN)	40℃, 60℃	1, 3, 5 days
	AIBN control	40℃, 60℃	1, 3, 5 days
Photolytic	Light, 1 X ICH	NA	1, 3, 5 days
	Light, 3 X ICH	NA	1, 3, 5 days
	Light control	NA	1, 3, 5 days
Thermal	Heat chamber	60℃	1, 3, 5 days
	Heat chamber	60℃	1, 3, 5 days
	Heat chamber	80℃	1, 3, 5 days
	Heat chamber	80℃	1, 3, 5 days
	Heat chamber	Room temp.	1, 3, 5 days

3.4 Guidelines for stress testing:

According to ICH guidelines on impurities in new drug products, degradation products if defined as a chemical variable in the drug molecule brought about over time and by the action of, for example, temperature, light, pH, or water/by reaction with an excipient or immediate container or closure system (also called decomposition sample).

From a regulatory perspective, stress testing studies provide data to support the following:

· Identify possible degradants.

· Degradation pathway and intrinsic stability of the drug molecule.

· Validation of stability-indicating analytical process. ³⁴

a. ICH Q1A: Stability Testing of New Drug Substances and Products,

b. ICH Q1B: Photostability Testing of New Drug Substances and Products,

c. ICH Q2B: Validation of Analytical Procedures: Methodology.

ICH Q1A (Stress testing):

Recommended conditions for performing forced degradation studies on drug substances and drug products. The recommendations are to inspect the results of temperature (above that for accelerated testing, i.e., >50 C), humidity (75% relative humidity), oxidation, and photolysis. A wide pH range should be considered in the testing of solution or suspension. Ultimately the stability-indicating method was developed by these samples.

ICH Q1B:

Recommended approaches to assessing the photostability of drug substances and drug products. For drug substance and drug product forced degradation conditions are specified in Section II and Section III respectively. Forced degradation studies exposure levels are not defined. Solid or in solution/suspension, photostability testing can be performed. These samples are then used to develop a stability-indicating method. Some of the degradation products formed during forced degradation studies may not be experiential to form during stability studies in which case they need not be examined further.

ICH Q2B:

Gives guidance to validate the analytical methodology. To prove specificity, in (impurities not available) there is a suggestion to utilize samples from forced degradation studies. Whether the analytical method is stability-indicating or not ‘specificity’ is a key factor.³⁵

3.5 Limitation of stress testing:

· Degradation of drug substances between 5% - 20% has been allowed for validation of chromatographic evaluation.

· It is not necessary that stress degradation would result in a degradation product.

· If no degradation is seen after drug substance or drug product has been displaying to stress condition then the stress study should be terminated.

· It is recommended that the highest of 14 days for stress testing in solution to provide a stressed sample for method development.¹⁶

· Stress testing was carried out to produce representative samples for developing a stability-indicating method for drug substances and drug products.

· The criteria of selecting stress conditions should depend upon the decomposition of the product under normal manufacturing, uses condition, and storage specifications which are specific and different for each drug substance and product.²³

4. How to validate this method

(parameter of validation):

AQbD method validation approach is that the validation of the analytical method over a range of different API batches. It uses both designs of experiment and method operable design region knowledge for designing method validation for all kinds of API manufacturing change without revalidation. The approach provides the required ICH validation elements as well as information on interaction, measurement uncertainty, control strategy, and continuous improvement. This approach requires fewer resources than the traditional validation approaches without compromising quality.³⁶The objective of validation of an analytical procedure is to indicate that it is suitable for its intended purpose. A tabular summation of the characteristics applicable to identification, control of impurities, and assay procedures is included. Other analytical procedures may be considered in future additions to these documents.²

Table 6: parameter of validation:³⁷

Performance characteristic	Definition (term)
Accuracy	The closeness of test results to the true value
Specificity	The ability to assess unequivocally the analyte in the presence of another compound that may be expected to be present
Linearity	Ability to elicit test results that are directly, or by a well-defined mathematical modification, proportional to the concentration of the analyte in a product within a given range
Precision	The degree of agreement among singlet test results
Detection limit	A characteristic of limit tests: the lower amount of analyte in a product that can be detected
Qualification limit	The lower amount of analyte in a product that can be determined with acceptable precision and accuracy
Range	The interval between the upper and lowest levels of analyte that is determined with a suitable level of precision, accuracy, and linearity
Robustness	Volume to remain unaffected by small but deliberate differences in procedural parameters listed in the process documentation and indicates its suitability during normal use.

5. ADVANTAGES OF AQBD:

· Scientific knowledge of pharmaceutical process and method

· Avoid regulatory compliance problems

· Reduction in variability in analytical attributes for development the method robustness

· Minimize deviation and costly inspection. It allows continuous development till the complete steps of a method.⁶

· AQbD concept in product improvement can be pointed out.

· The regulation is flexible.

· The changes of a product inside the design area are not seen as a variation in development.

· Sources of variability can be benefits control.³⁸

· A better understanding of the process.

· Less batch failure.

· More efficient and control of change.³⁹

6. APPLICATION OF AQBD:

· Understand, reduce and control sources of variability and Applicable throughout the life cycle of the method.²⁸

· Improves information in regulatory submission

· Ensure decisions made on sciences and not on empirical information.

· Provides for better consistency

· Provides for better coordination across a review, compliance, and inspection.

· Involves various disciplines in decision making.⁴⁰

6.1 Other application:

· Methods that characterize excipients may also improve from the analytical QBD approach.

· Finally, the analysis of biopharmaceutical samples is a space where AQBD approaches would be beneficial.

· The chromatographic method like HPLC (for stability studies, method improvement, and determination of impurities in pharmaceuticals).

· A hyphenated technique like LC-MS.

· An advanced method like mass spectroscopy, UHPL, and capillary electrophoresis

· Dissolution studies^.40

7. CONCLUSION:

Quality by design (QbD) has gain importance in the area of pharmaceutical processes like drug development, formulations, analytical method, and biopharmaceuticals. Analytical quality by design plays a key role in the pharmaceutical industry for ensuring product quality. The goal of a well-characterized method development effort is to develop a reliable method that can be demonstrated with a high produce data meeting predefined criteria when operated within defined boundaries. QbD can be applied to the development and evaluation of an analytical method. Stress testing is a very important tool in pharmaceutical research and development to develop a stable formulation. It provides information about degradation pathways of drug substances and drug products, which can be used in excipient compatibility and provide help in early-stage development. Any strategy used for forced degradation aims to produce the desired amount of degradation i.e., 5-20%. A properly designed and executed forced degradation study would generate an appropriate sample for the development of the stability-indicating method.

8. REFERENCES:

1. Maapatra A and Meyyanathan SN. Analytical Quality by Design-A review. Indian research journal of pharmacy and science. 2020; 7(2): 2132-2140.

2. Bhvani GP and Devi AD. Development and Validation of Stability Indicating UPLC Method for the Simultaneous Estimation of Drugs in Combined Dosage Forms using Quality by Design Approach. Asian Journal of Pharmaceutical Analysis. 2020; 10(3): 1-19.

3. ICH – Harmonized Tripartite Guideline, “Photo Stability testing of New drug substance and products Q1B”, International Conference on Harmonization, IFPMA, Geneva, Switzerland, 1996;

4. Gaykar D and Khadse SC. A Review on Analytical quality by design. International journal of pharmaceutical science review and research. 2017; 44(2): 96-102.

5. Darkunde SL. A review on quality by design. International journal of pharmaceutical chemistry and analysis.2018, 5(1), 1-6.

6. Jethani JM and Pai GK A. comparative review of the USFDA guidelines on process validation focusing on the importance of quality by design (QbD). Research Journal of Pharmacy and Technology. 2017; 10(4): 1-17.

7. Phadtare DP, Pawar A and Saudagar RB. A Brief Review on Quality by Design and Process Analytical Technology. Asian Journal of Pharmaceutical Analysis. 2016; 6(2): 1-21.

8. Das P and Maity A. Analytical Quality by Design (AQBD): A New Horizon for Robust Analytics in Pharmaceutical Process and Automation. International journal of pharmaceutics and drug analysis. 2017; 5(8): 324-337.

9. Patil KA and Dinkar SF. Determination and Development of UV-Spectrophotometric method for the Amodiquine Hydrochloride by using quality by design (QbD) approach. Asian Journal of Pharmaceutical Analysis. 2019; 9(3): 1-18.

10. Ganorkar AV and Gupta KR. Analytical Quality by Design: A Mini Review. Biomedical journal of scientific and technical research. 2017; 1(6): 1555-1558.

11. Bhutani H and Kurmi M, et.al. Quality by Design (QbD) in Analytical Science: An Overview. Pharma Times. 2014; 46(8): 71-75.

12. Das v, Bhusan B and Saudagar RB. Quality by design approaches to analytical method development. Research Journal of Pharmacy and Technology. 2017; 10(9): 1-21.

13. Peraman R, Bhadraya K and Reddy YP. Analytical Quality by Design: A Tool for Regulatory Flexibility and Robust Analytics. International Journal of Analytical Chemistry. 2015; 1-9.

14. Phadke R, et. al., A review on quality by design approaches to analytical method development. Indo American of pharmaceutical research. 2019; 9(7): 3044-3055.

15. Chavan SD, et. al., Quality by Design. Asian Journal of Research in Pharmaceutical Sciences. 2016; 6(1): 1-19.

16. Tambe K and Bonde S. A review on: Application of pharmaceutical quality by design in product development. Word journal of pharmaceutical science. 2017; 5(1): 58-70.

17. Kadam VR, et. al., A Review on: Quality by Design (QbD). Asian Journal of Research in Pharmaceutical Sciences. 2017; 7(4): 1-20.

18. Pramod K, et al., Pharmaceutical product development: A quality by design approach. International Journal Pharmaceutical Investing. 2016; 6(3): 129-138.

19. Ramalingam P, Kalva B and reddy Y. Analytical Quality by Design: A Tool for Regulatory and Robust Analytics. International Journal of Analytical Chemestry. 2015; 9.

20. Baertschi SW and Reyooldes DW. Pharmaceutical Stress Testing. Taylor and Francis 2005; pp-2.

21. Kumar SA, et.al., Stability indicating Method Development and Validation for simultaneous estimation of Hydrochlorothiazide, Amlodipine and Olmesartan in tablet dosage form by using RP-HPLC. Asian Journal of Research in Chemistry. 2014; 7(5): 1-21.

22. Steven WB and Patrick JJ. Pharmaceutical stress Testing. Taylor and Francis 2005, pp-16.

23. Thakor KA, Bhavsar DD and Thakor JR. International Journal of Research in Pharmacology and Pharmacotherapeutics. International Journal Research Pharmacology and Pharmacotherapeutics. 2016; 5(4): 291-297.

24. Venkataraman S and Manasa M. Forced degradation studies: Regulatory guidance, Characterization of drugs, and their degradation products- a review. 2018; 10(16): 137-143.

25. Sharma MK and Murugesan M. Forced degradation study an essential Approach to Development Stability Indicating Method. Journal of Chromatography Seperation Techniques. 2017; 8(1): 1-3.

26. Deokate U and Gorde AM. Forced Degradation and Stability Testing: Strategies and Analytical Perspectives. International journal Pharmaceutical Science Review and Research. 2014; 26(2): 242-250.

27. Blessy M, et.al., Development of forced degradation and stability indicating studies of drugs- A review. Journal of Pharmaceutical Analysis. 2013; 4(3): 159-165.

28. Basha MD, et.al., A Review on Forced Degradation Studies and Its Importance in Analytical Method Development and Validation. International Journal of Innovative Pharmaceutical Science and Research. 2014; 2(11): 2929-2940.

29. Roge AB et.al., Forced Degradation Study: An Important Tool in Drug Development. Asian Journal of Research in Chemistry. 2014; 7(1): 1-16.

30. Rawat T and Pandy IP. Forced degradation studies for drug substances and drug product –Scientific and Regulatory Considerations. Journal of Pharmaceutical Sciences and Research 2015; 7(5): 238-241.

31. Patel D and Patel M. A Review article on Development of Forced Degradation and stability indicating studies for drug substance and drug product. Journal of Pharmaceutical Science and bioscientific research. 2019; 9(2): 165-172.

32. Hotha KK, et.al., forced degradation studies: practical approach –overview of regulatory guidance and literature for the drug products and drug substances. International research journal of pharmacy. 2013; 4(5): 78-85.

33. Ngwa G. Forced degradation as an integral part of HPLC Stability- Indicating method Development. Drug Delivery Technology. Drug delivery technology. 2010; 10(5): 1-4.

34. Alsante KM, et al., Degradation and Impurity Analysis for Pharmaceutical Drug Candidates. Elsevier Inc. 2011; Pp.60-61.

35. Iram F, et.al., Forced Degradation Studies. Journal of analytical and pharmaceutical research. 2016; 3(6): 1-5.

36. Ghove SB, et.al., Analytical method development and validation by QbD approach-A review. Pelagia research library. 2015; 6(8): 18-24.

37. Reid GL, et.al., Analytical quality by design (AQBD) in pharmaceutical Development. American Pharmaceutical review. 2013; 1-12.

38. Alhakeem MB, et.al., Analytical quality by design with the Life-cycle Approach: A Modern Epitome for Analytical Method Development. Acta Medica Marisiensiensis. 2019; 65(2): 37-44.

39. Kengar MD, Tamboli JA and Magdum CS. Quality by Design in Pharmaceutics. Research Journal of Pharmaceutical Dosage Forms and Technology. 2019; 11(3): 1-16.

40. Goswami S and Chakraverty R. A Review on Application of Quality by Design concept to Analytical Techniques. Internatinal Journal of Current Research In Health And Biological Sciences. 2016; 1(3): 100-108.

Received on 06.01.2021 Revised on 17.02.2021

Asian Journal of Pharmaceutical Analysis. 2021; 11(2):170-178.

DOI: 10.52711/2231-5675.2021.00029