Introduction for Process Validation
Process validation is one of the most important activities in pharmaceutical manufacturing. In an Oral Solid Dosage (OSD) facility, products such as tablets and hard gelatin capsules pass through several manufacturing stages, including dispensing, sifting, granulation, drying, milling, blending, lubrication, compression or encapsulation, coating and packing.
A good process validation procedure provides documented evidence that the manufacturing process can consistently produce a product meeting its predefined quality requirements.
FDA describes three broad stages: Process Design, Process Qualification and Continued Process Verification (CPV).
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What Is Process Validation?
Process validation is a documented, science-based activity used to demonstrate that a manufacturing process is capable of consistently producing a product that meets predetermined quality attributes and specifications.
For an OSD product, this means demonstrating that the complete manufacturing process—from dispensing through the relevant finished-product stage—operates in a controlled and reproducible manner.
Dispensing → Sifting → Granulation → Drying → Milling → Blending → Lubrication → Compression → Coating → Packing
Process validation should not simply demonstrate that the final tablets pass testing. It should provide evidence that the important manufacturing steps and process parameters are appropriately controlled.
FDA’s lifecycle approach connects process understanding, process qualification and ongoing monitoring rather than treating validation as a one-time exercise.
Why Is Process Validation Required?
The primary purpose of process validation is to provide confidence that the manufacturing process can repeatedly produce acceptable product.
In practical OSD manufacturing, validation helps to:
- Identify sources of process variation.
- Establish appropriate process parameters.
- Confirm equipment and process capability.
- Demonstrate reproducibility between batches.
- Confirm that critical quality attributes remain under control.
- Establish appropriate sampling and monitoring requirements.
- Reduce the possibility of batch failures.
- Support regulatory submissions and inspections.
- Provide a scientific basis for continued process monitoring.
- Support changes to equipment, materials, batch size or manufacturing parameters.
The important point is that validation is not merely three batches passing final product testing. The manufacturer should understand why the process works and how important sources of variability are controlled.
FDA specifically emphasizes understanding sources of variation, detecting and measuring variation, understanding its effect on product quality and controlling variation according to risk.
Regulatory and GMP Expectations
Several major regulatory and GMP principles influence process validation for OSD products.
FDA Process Validation
The FDA’s Process Validation: General Principles and Practices guidance uses a lifecycle model consisting of:
- Stage 1 – Process Design
- Stage 2 – Process Qualification
- Stage 3 – Continued Process Verification
The objective is to establish scientific evidence that the process is capable of consistently producing quality product.
Importantly, FDA does not prescribe a universal minimum number of validation batches. The manufacturer should establish the number scientifically and provide an appropriate rationale.
ICH Q8, Q9 and Q10
ICH Q8 supports pharmaceutical development and process understanding. ICH Q9 provides the framework for quality risk management, while ICH Q10 describes the pharmaceutical quality system.
Together, these concepts support a science- and risk-based validation strategy.
ICH materials also recognize that risk assessment can help develop validation plans and that statistical monitoring can support continued assurance of process control.
European GMP Expectations
EMA guidance expects the manufacturing process for finished products to be validated before the product is placed on the market, subject to applicable regulatory provisions and exceptional circumstances. It also recognizes traditional process validation, continuous process verification and combinations of these approaches.
Detailed Process Validation Procedure for OSD
A practical process validation program can be divided into the following stages.
Select the Product for Validation
Before preparing the protocol, identify the product to be validated.
The selection should consider:
- Product dosage form
- Strength
- Batch size
- Manufacturing process
- Equipment train
- Manufacturing site
- Product complexity
- Previous manufacturing experience
- Regulatory commitments
- Existing process knowledge
For products having multiple strengths or batch sizes, a scientifically justified bracketing or matrixing approach may sometimes be appropriate.
The justification should be documented rather than assuming that one validated batch automatically represents every strength and batch size.
Review Product and Process Knowledge
Before validation begins, review the available development and manufacturing information.
Important documents may include:
- Master Formula Record
- Batch Manufacturing Record
- Product development report
- Technology transfer documents
- Risk assessments
- Previous validation studies
- Scale-up studies
- Stability information
- Specifications
- Analytical method validation
- Equipment qualification documents
- Cleaning validation information
- Change controls
- Deviations and investigations
This review provides the foundation for determining what needs to be challenged during validation.
Identify CQAs
CQA means Critical Quality Attribute.
A CQA is a physical, chemical, biological or microbiological characteristic that should be within an appropriate limit, range or distribution to ensure product quality.
For an OSD tablet, CQAs may include:
| Product | CQA |
| Tablet | Assay |
| Tablet | Content uniformity |
| Tablet | Dissolution |
| Tablet | Related substances |
| Tablet | Hardness |
| Tablet | Friability |
| Tablet | Weight variation |
| Tablet | Disintegration |
| Tablet | Appearance |
| Coated tablet | Coating uniformity |
| Capsule | Assay |
| Capsule | Content uniformity |
| Capsule | Dissolution |
| Capsule | Weight variation |
Not every attribute will necessarily be a CQA. The designation should be scientifically justified based on product knowledge and risk.
Identify CPPs
CPP means Critical Process Parameter.
These are process parameters whose variability can affect a CQA and therefore need to be appropriately controlled.
Examples in OSD manufacturing include:
| Process Step | Possible Process Parameters |
| Sifting | Screen size, operating time |
| Granulation | Binder quantity, addition rate, impeller speed |
| Wet granulation | Granulation time, endpoint |
| Drying | Inlet temperature, product temperature, drying time |
| Milling | Screen size, mill speed |
| Blending | Blender speed, blending time |
| Lubrication | Lubrication time, blender speed |
| Compression | Compression force, turret speed, feeder speed |
| Coating | Spray rate, inlet temperature, product temperature |
| Encapsulation | Machine speed, fill-weight settings |
These are examples only. The actual CPPs should be established from product and process knowledge and documented risk assessment.
Perform Process Risk Assessment
A risk assessment should be performed before finalizing the validation protocol.
Common tools include:
- FMEA
- Fishbone analysis
- HACCP
- Risk ranking
- Process mapping
For example, in a tablet compression process:
High compression force → increased tablet hardness → possible effect on disintegration/dissolution
This relationship should be considered when establishing the control strategy and validation sampling plan.
The purpose of risk assessment is not to create a complicated document. Its purpose is to identify where process variability can have a meaningful impact on product quality.
Prepare the Process Validation Protocol
The protocol should be approved before execution.
A practical protocol should include:
Product Information
- Product name
- Strength
- Dosage form
- Batch size
- Manufacturing site
- Manufacturing equipment
Validation Objective
Clearly state what the study is intended to demonstrate.
Scope
Define the manufacturing steps covered by the validation.
Responsibilities
Clearly assign responsibilities to:
- Production
- Quality Assurance
- Quality Control
- Engineering
- Validation
- R&D or Technology Transfer, where applicable
Process Description
Describe the manufacturing process in sufficient detail.
Critical Parameters
Identify CPPs and their operating ranges.
Critical Quality Attributes
List relevant CQAs and acceptance requirements.
Sampling Plan
Define:
- Sampling locations
- Sampling quantity
- Sampling frequency
- Sample identification
- Testing requirements
- Responsible department
Acceptance Criteria
Predefine acceptance criteria before execution.
Deviations
Define how deviations observed during validation will be documented and evaluated.
Confirm Equipment and Utilities Are Qualified
Process validation should not be used to qualify an unqualified manufacturing system.
Before execution, confirm that relevant:
- Manufacturing equipment
- Utilities
- Instruments
- HVAC systems
- Weighing systems
- Temperature monitoring systems
- Compressed air systems
- Water systems
- Computerized systems
are appropriately qualified or otherwise demonstrated to be suitable for their intended use.
ICH implementation materials specifically emphasize that facilities, equipment and relevant computerized systems should be suitably qualified and personnel appropriately trained.
Verify Analytical Methods
The tests used to evaluate validation samples should be performed using approved and appropriately validated or otherwise qualified analytical procedures, as applicable.
For an OSD process validation study, QC may test:
- Description
- Identification
- Assay
- Content uniformity
- Dissolution
- Related substances
- Water/moisture
- Disintegration
- Hardness
- Friability
- Microbial quality, where applicable
The testing plan should be scientifically linked to the product and process risks.
Manufacture Validation Batches
Validation batches should be manufactured using the intended commercial manufacturing process and appropriately representative conditions.
Production personnel should follow the approved manufacturing procedure.
Important information should be recorded during execution, including:
- Material quantities
- Equipment identification
- Equipment settings
- Environmental conditions where relevant
- Process parameters
- Start and end times
- In-process test results
- Yield
- Sampling activities
- Deviations
- Interventions
- Equipment alarms
- Any unusual observations
The goal is to demonstrate the actual manufacturing process—not an artificially simplified laboratory version of it.
Perform Enhanced Sampling During Validation
Validation normally involves more detailed monitoring than routine manufacturing.
For example, during blending, samples may be taken from multiple locations to evaluate blend uniformity.
During compression, samples may be collected at:
- Beginning
- Middle
- End
Additional samples may be taken when justified by risk.
For coating, monitoring may include:
- Weight gain
- Appearance
- Coating parameters
- Product temperature
- Spray rate
- Inlet/outlet conditions
The sampling plan should be designed to detect potential variability rather than simply generate a large number of samples.
Evaluation In-Process Results
In-process results should be reviewed against predetermined requirements.
Examples include:
- Blend uniformity
- Granule moisture
- Granule particle size
- Tablet weight
- Tablet hardness
- Thickness
- Friability
- Compression force
- Coating weight gain
Trending is particularly useful because a process can technically remain within specification while showing an undesirable trend.
Evaluation of Finished Product Results
Each validation batch should be evaluated against the approved finished-product specifications.
Typical tests for tablets may include:
- Description
- Identification
- Assay
- Uniformity of dosage units
- Dissolution
- Related substances
- Disintegration
- Friability, where applicable
For capsules, the testing strategy should be appropriate to the dosage form and product.
All results should be scientifically reviewed rather than considering only whether the final specification was passed.
Evaluate Yield and Material Reconciliation
Yield is an important process performance indicator.
Evaluate:
- Theoretical yield
- Actual yield
- Percentage yield
- Stage-wise yield
- Material reconciliation
- Rejects
- Process losses
Unexpected changes in yield can sometimes indicate process problems even when the finished product meets specifications.
Compile and Approve the Validation Report
After completion of the validation batches, prepare a validation report.
The report should summarize:
- Objective
- Scope
- Protocol reference
- Batch details
- Manufacturing equipment
- Process parameters
- Sampling results
- In-process results
- Finished-product results
- Yield
- Deviations
- Investigations
- Statistical analysis
- Trend evaluation
- Acceptance criteria assessment
- Conclusion
The final conclusion should clearly state whether the process has demonstrated an acceptable level of control.
FDA’s validation principles emphasize objective data and evidence demonstrating reproducibility rather than simply relying on assumptions.
PV Practical Implementation in Plant
A simple way to visualize the implementation is:
Product Development
↓
Process Understanding
↓
Risk Assessment
↓
Identify CQAs & CPPs
↓
Validation Protocol
↓
Equipment/Utility Qualification
↓
Validation Batch Manufacturing
↓
Enhanced Sampling & Testing
↓
Data Analysis
↓
Deviation Evaluation
↓
Validation Report
↓
QA Approval
↓
Continued Process Verification
This approach makes process validation a controlled activity rather than a paperwork exercise.
Acceptance Criteria
Acceptance criteria should be established before validation begins.
They should be scientifically justified and linked to the product, process and applicable specifications.
For example:
| Parameter | Example Acceptance Criteria |
| Assay | Within approved product specification |
| Dissolution | Meets approved specification |
| Blend uniformity | Meets predefined criteria |
| Granule moisture | Within established process range |
| Tablet weight | Within approved in-process limits |
| Tablet hardness | Within established range |
| Friability | Within approved requirement |
| Coating weight gain | Within predefined target/range |
| Yield | Within established validated range |
| CPPs | Within approved operating/validation range |
A validation protocol should not be written in a way that allows the acceptance criteria to be decided after seeing the results.
Common Mistakes in during Process Validation
Focusing Only on Finished Product Testing
Passing final product testing does not automatically prove that the manufacturing process is well controlled.
The process itself must be understood and evaluated.
Poor Sampling Strategy
Taking samples without considering process risk can result in a large amount of data that provides little useful information.
Using Unqualified Equipment
Validation performed on equipment that has not been appropriately qualified creates a major weakness in the validation program.
Changing Parameters During Validation Without Assessment
Changes to important process parameters during validation should be properly documented and scientifically assessed.
Process Validation Documentation
A robust OSD process validation package may contain the following:
| Document | Purpose |
| Validation Master Plan | Defines overall validation strategy |
| Process Risk Assessment | Identifies process risks |
| Process Validation Protocol | Defines how validation will be performed |
| Approved MFR/BMR | Defines manufacturing process |
| Equipment Qualification | Confirms equipment suitability |
| Calibration Records | Confirms measurement reliability |
| Training Records | Confirms personnel qualification |
| Sampling Plan | Defines validation sampling |
| Analytical Results | Provides quality evidence |
| In-Process Results | Demonstrates process control |
| Finished Product Results | Confirms product quality |
| Investigation/CAPA | Addresses significant issues |
| Process Validation Report | Summarizes study conclusions |
Manufacturing Process in Process Validation
Dispensing → Sifting → Wet Granulation → Drying → Milling → Blending → Lubrication → Compression → Packing
Potential CQAs during Process Validation
- Assay
- Content uniformity
- Dissolution
- Related substances
- Tablet weight
- Hardness
- Friability
- Disintegration
Potential CPPs during Process Validation
| Process | Potential CPP |
| Granulation | Impeller speed |
| Granulation | Binder addition rate |
| Granulation | Granulation time |
| Drying | Product temperature |
| Drying | Moisture endpoint |
| Milling | Screen size |
| Blending | Blending time |
| Lubrication | Lubrication time |
| Compression | Compression force |
| Compression | Machine speed |
| Coating | Spray rate |
| Coating | Product temperature |
The actual CPP designation should be based on product/process understanding and risk assessment, not simply because a parameter appears on the machine.
FAQs for Process Validation
What is process validation in pharmaceutical manufacturing?
Process validation is the documented demonstration that a manufacturing process can consistently produce a quality product.
Is process validation mandatory for products?
Yes, Process validation is mandatory for each and every products. Manufacturers are expected to demonstrate that their commercial manufacturing processes are capable of consistently producing acceptable quality products.
How many batches are required for process validation?
There is no universal FDA requirement that every product must have exactly three validation batches. The number should be scientifically justified based on process knowledge, complexity and risk.
What are CPP and CQA?
CPP means Critical Process Parameter, while CQA means Critical Quality Attribute. CPPs relate to process variables that can affect product quality, while CQAs are product characteristics important for ensuring the required quality.
What is the difference between PPQ and process validation?
Process Performance Qualification (PPQ) is an important part of the process validation lifecycle, particularly in the qualification stage. Process validation is broader and encompasses lifecycle activities from process design through ongoing verification.