Pharmaceutical quality cannot depend only on testing the finished product. Quality must be controlled throughout the manufacturing process to ensure that each critical step is performed within approved requirements. In-process checks in pharmaceutical manufacturing help production and quality teams monitor important process parameters, identify abnormalities early, and prevent defects from progressing to later stages.
Depending on the dosage form and manufacturing process, in-process checks may include weight variation, blend uniformity, hardness, thickness, pH, fill volume, temperature, appearance, yield, and other process-specific parameters. These checks are performed according to approved procedures and predefined acceptance criteria.
Effective in-process controls support GMP compliance, consistent product quality, and reliable batch documentation.
What Are In-Process Checks in Pharmaceutical Manufacturing?
In-process checks in pharmaceutical manufacturing are documented checks, measurements, inspections, or tests performed during manufacturing or processing to confirm that the process is operating within established requirements.
They may be performed by production personnel, in-process quality control personnel, or other authorized personnel, depending on the site’s procedures and responsibilities.
The purpose is not simply to collect data. In-process checks help determine whether a manufacturing step is progressing as intended and whether corrective action or investigation is necessary.
Examples include:
- Weight checks
- Appearance checks
- pH measurement
- Temperature monitoring
- Mixing time verification
- Blend or solution checks
- Tablet hardness
- Tablet thickness
- Friability
- Disintegration
- Fill volume
- Yield and reconciliation
- Environmental or process-condition checks
The exact checks depend on the product, manufacturing process, validated process, and approved batch documentation.
Why Are In-Process Checks Important?
GMP emphasizes building quality into manufacturing rather than relying only on final testing. In-process controls are therefore an important part of pharmaceutical manufacturing because they help identify process problems before they affect an entire batch.
Key benefits include:
1. Early detection of process problems
An abnormal result can be identified while manufacturing is still in progress.
2. Prevention of batch defects
Timely intervention can prevent an identified process issue from affecting subsequent manufacturing steps.
3. Process consistency
Regular checks help demonstrate that manufacturing is being performed within established operating requirements.
4. Support for batch release decisions
In-process results become part of the batch documentation reviewed during overall batch assessment.
5. GMP compliance
Documented in-process controls demonstrate that critical manufacturing activities are monitored and controlled.
6. Reduced risk of rejection
Early detection of deviations can reduce the possibility of producing a batch that does not meet established requirements.
WHO GMP principles identify the evaluation and performance of in-process controls as part of pharmaceutical quality assurance, while emphasizing documented procedures, records, process validation, and investigation of significant deviations.
10 Important In-Process Checks in Pharmaceutical Manufacturing
The following are common examples. Not every product requires all ten.
1. Weight Variation and Weight Checks
Weight checks are important for products such as tablets, capsules, powders, granules, and filled containers.
For tablet manufacturing, periodic individual tablet weights may be checked to identify variation during compression.
For liquid or semi-solid products, fill weight or fill volume may be monitored.
Possible causes of abnormal weight variation include:
- Inconsistent powder or granule flow
- Feed-system problems
- Machine settings
- Segregation
- Filling-system variation
- Equipment malfunction
If results fall outside the established requirements, the issue should be assessed according to the approved procedure.
2. Appearance Checks
Appearance checks can be performed at different stages of manufacturing and packaging.
For tablets, analysts or operators may check for:
- Cracks
- Capping
- Chipping
- Lamination
- Mottling
- Broken tablets
- Abnormal colour
For capsules, checks may include:
- Capsule integrity
- Colour
- Filling condition
- Damage or deformation
For liquids and other dosage forms, appearance may include colour, clarity, homogeneity, or the presence of visible foreign matter as applicable to the product.
Appearance checks can help identify manufacturing problems before the batch progresses further.
3. Hardness of Tablets
Tablet hardness is an important physical parameter monitored during tablet compression.
Changes in compression force or formulation behaviour can affect tablet hardness.
Hardness that is too low may contribute to problems such as:
- Tablet breakage
- Chipping
- Handling damage
Excessive hardness may potentially affect other performance characteristics, depending on the formulation and process.
Therefore, hardness should be evaluated together with other applicable tablet-quality parameters rather than considered in isolation.
4. Tablet Thickness
Tablet thickness can be monitored during compression to identify variation in tablet dimensions.
Changes may occur because of:
- Compression settings
- Granule properties
- Tooling
- Machine conditions
- Fill variation
Consistent thickness can also be important during subsequent coating and packaging operations.
5. Disintegration and Friability Checks
Depending on the product and approved manufacturing controls, disintegration and friability may be monitored as in-process or process-control tests.
Disintegration evaluates how a dosage form breaks down under specified test conditions.
Friability evaluates the tendency of tablets to lose mass under defined mechanical stress.
These tests can provide useful information about the physical characteristics of tablets and the impact of manufacturing conditions.
The applicable testing frequency and acceptance criteria should always come from the approved product-specific procedure.
6. pH Checks
pH is an important process parameter for many liquid, ophthalmic, topical, and other formulations where pH can affect product quality.
Incorrect pH can potentially influence:
- Product stability
- Solubility
- Compatibility
- Preservative performance
- Product performance
Before testing, the pH meter should be in the required operational and calibration/verification status according to laboratory procedures.
Results should be recorded accurately and compared with the approved process requirement.
7. Temperature Checks
Temperature can be a critical process parameter in many pharmaceutical manufacturing operations.
Examples include:
- Heating
- Cooling
- Mixing
- Solution preparation
- Granulation
- Sterilization-related processes
- Storage of intermediates
Failure to maintain required temperature conditions may affect product quality or process performance.
Temperature monitoring may therefore be performed using calibrated or appropriately controlled monitoring equipment.
8. Mixing Time and Mixing Conditions
Mixing is an important operation in the manufacture of many pharmaceutical products.
Inadequate mixing can contribute to problems such as:
- Non-uniform distribution of components
- Inconsistent product characteristics
- Processing variability
Mixing time, speed, temperature, order of addition, and other parameters may be defined within the manufacturing process.
Operators should follow the approved batch manufacturing instructions rather than making unauthorized adjustments based on observation alone.
9. Fill Volume or Fill Weight
For liquid and semi-solid products, fill volume or fill weight can be an important in-process check.
Examples include:
- Oral liquids
- Suspensions
- Creams
- Ointments
- Lotions
Inappropriate filling conditions can result in underfilled or overfilled containers.
Possible causes include:
- Filling-machine settings
- Pump variation
- Product viscosity
- Air entrapment
- Nozzle problems
- Equipment malfunction
Regular checks can help identify filling variation during production.
10. Yield and Reconciliation
Yield calculations and material reconciliation are important manufacturing controls.
Yield compares the expected quantity with the actual quantity obtained at a defined manufacturing stage.
Reconciliation may involve materials, bulk product, components, or packaging materials as applicable.
Unexpected discrepancies can indicate:
- Material loss
- Process problems
- Calculation errors
- Documentation errors
- Spillage
- Equipment retention
- Potential mix-up or other abnormal event
Significant discrepancies should be investigated according to the applicable procedure.
Examples of In-Process Checks by Dosage Form
| Dosage Form | Possible In-Process Checks |
|---|---|
| Tablets | Weight, hardness, thickness, appearance, friability, disintegration |
| Capsules | Fill weight, appearance, capsule integrity |
| Oral liquids | pH, appearance, volume, temperature, mixing parameters |
| Suspensions | pH, appearance, viscosity, mixing/homogeneity-related controls |
| Creams/Ointments | Appearance, homogeneity, viscosity, fill weight |
| Powders/Granules | Moisture, particle characteristics, blend/process controls |
| Parenteral products | Process-specific controls, fill volume, environmental/process parameters |
| Packaging | Fill count, coding, seal integrity, appearance, reconciliation |
The actual in-process control strategy should always be based on the individual product and validated manufacturing process.
In-Process Checks vs Finished Product Testing
These two activities are related but serve different purposes.
| In-Process Checks | Finished Product Testing |
|---|---|
| Performed during manufacturing | Usually performed on completed product |
| Helps monitor the process | Helps assess finished-product quality |
| Can identify problems early | Provides final analytical/quality information |
| Product/process-specific | Based on approved finished-product specifications |
| May be performed at multiple stages | Generally performed after completion of manufacturing |
| Supports process control | Supports final quality assessment and release |
In-process controls do not eliminate the need for required finished-product testing.
In-Process Check vs Process Parameter
These terms are sometimes confused.
A process parameter is a variable or condition associated with a manufacturing process, such as mixing speed, temperature, pressure, or time.
An in-process check is a defined check or measurement used to monitor whether a process or product characteristic is within the established requirement.
For example:
Process parameter: Mixing speed = specified operating condition
In-process check: Testing or verification of a defined product characteristic after the mixing operation
The relationship between process parameters and product quality should be established through process understanding and validation.
Role of Production in In-Process Checks
Production personnel play an important role in performing and documenting manufacturing operations.
Their responsibilities may include:
- Following approved manufacturing instructions
- Performing assigned checks
- Recording results contemporaneously
- Monitoring equipment and process conditions
- Reporting abnormalities
- Maintaining equipment and area conditions
- Following approved procedures for deviations
Production personnel should not independently alter established process conditions without appropriate authorization.
Role of QA in In-Process Checks
QA provides oversight of the pharmaceutical quality system and ensures that manufacturing activities are performed according to approved requirements.
Depending on the site’s organizational structure, QA may be involved in:
- Review of batch records
- Review of deviations
- Change control
- CAPA
- Investigation of discrepancies
- GMP compliance
- Documentation review
- Process and procedure approval
- Audit readiness
- Batch record assessment
QA should ensure that significant abnormalities are appropriately documented and investigated.
Role of QC in In-Process Testing
QC may perform analytical or laboratory-based in-process tests depending on the manufacturing process and site responsibilities.
Examples may include:
- pH testing
- Moisture testing
- Assay-related testing
- Microbiological testing
- Specific physical tests
- Sampling and laboratory analysis
The exact responsibilities of QC and production vary between organizations and processes.
What Happens When an In-Process Check Fails?
An in-process result outside its established requirement should not simply be ignored or corrected without assessment.
A general approach may include:
Step 1: Identify the abnormal result
Confirm the recorded result, calculation, sample identification, and applicable acceptance criteria.
Step 2: Inform the responsible personnel
The appropriate production, QC, and/or QA personnel should be notified according to site procedures.
Step 3: Assess the process condition
Review relevant equipment settings, process parameters, materials, environmental conditions, and manufacturing records.
Step 4: Determine whether the result is genuine
Any additional testing or checking must follow an approved procedure. Uncontrolled repeat testing should not be used simply to obtain a passing result.
Step 5: Initiate deviation or investigation when required
The event should be documented and investigated according to the applicable quality system.
Step 6: Identify root cause
Tools such as:
- 5 Why
- Fishbone/Ishikawa analysis
- Process mapping
- Failure mode analysis
may be used as appropriate.
Step 7: Implement appropriate actions
Corrective actions, preventive actions, process adjustments, or other measures should be implemented according to the investigation outcome.
Documentation of In-Process Checks
One of the most important principles is:
If a check is required, the result must be properly documented.
Records may include:
- Date and time
- Batch number
- Product name
- Manufacturing stage
- Equipment identification
- Parameter or test
- Result
- Acceptance criteria
- Name/initials or electronic identification
- Required verification
- Comments or observations
Documentation should follow applicable Good Documentation Practices and data-integrity requirements.
Records generated during manufacturing help establish the history of the batch and demonstrate that required manufacturing steps and controls were performed.
Common Mistakes in In-Process Checks
1. Recording results later
Results should be recorded according to approved documentation practices rather than reconstructed from memory.
2. Using incorrect acceptance criteria
The current approved batch record or procedure should be used.
3. Ignoring small abnormalities
Even apparently minor abnormalities may require assessment depending on their nature and potential impact.
4. Unauthorized process adjustments
Operators should not make undocumented changes to process conditions.
5. Repeating tests without justification
Repeat checks should be scientifically and procedurally justified.
6. Poor equipment identification
The equipment used for a check should be appropriately identified and its required status verified.
7. Incomplete documentation
Missing signatures, dates, times, results, or required verification can create GMP documentation issues.
In-Process Checks and GMP
In-process checks support the GMP principle that pharmaceutical quality should be built into the manufacturing process.
WHO GMP principles emphasize clearly defined and validated manufacturing processes, appropriate in-process controls, trained personnel, suitable equipment, written procedures, and records demonstrating that required manufacturing steps have been performed.
In-process checks therefore form part of a broader system involving:
Process Design → Qualification → Validation → Manufacturing → In-Process Controls → Documentation → Review → Final Product Testing → Batch Release
No single in-process test can guarantee overall product quality. Effective pharmaceutical manufacturing depends on the complete control strategy.
10 Points Every QA/QC Fresher Should Remember
For interviews, remember these points:
- In-process checks are performed during manufacturing.
- They help detect process problems early.
- Checks are product- and process-specific.
- Acceptance criteria must come from approved documents.
- Weight and appearance checks are common examples.
- pH, temperature, mixing, fill volume, and yield may also be monitored.
- In-process checks do not replace finished-product testing.
- Abnormal results must be assessed and documented.
- Uncontrolled repeat testing should be avoided.
- Proper documentation is essential for GMP compliance.
Common Interview Questions
What are in-process checks?
They are defined checks or tests performed during manufacturing to monitor process and product characteristics against established requirements.
Why are in-process checks important?
They help detect manufacturing problems early and support consistent product quality.
Give examples of in-process checks for tablets.
Examples include weight, hardness, thickness, appearance, friability, and disintegration, depending on the product and approved process.
What is the difference between in-process testing and finished-product testing?
In-process testing or checking is performed during manufacturing to monitor the process, while finished-product testing evaluates the completed product against its approved specifications.
What should you do if an in-process check fails?
The result should be verified and assessed according to the approved procedure. The appropriate personnel should be informed, and a deviation or investigation should be initiated when required.
Can an operator change the process after an in-process failure?
Not unless the change is permitted and appropriately authorized under the applicable procedure and quality system.
Who performs in-process checks?
This depends on the organization and process. Production, in-process QC, QC, or other authorized personnel may perform specific checks according to approved procedures.
Are in-process checks the same for every pharmaceutical product?
No. They depend on the dosage form, formulation, manufacturing process, critical process characteristics, validation strategy, and approved product documentation.
Frequently Asked Questions
What is the main purpose of in-process checks in pharmaceutical manufacturing?
Their main purpose is to monitor manufacturing operations and product characteristics during processing so that potential problems can be detected and addressed before they affect product quality.
What are common in-process checks for tablets?
Common examples include tablet weight, hardness, thickness, appearance, friability, and disintegration, where applicable.
Why is pH checked during pharmaceutical manufacturing?
For products where pH is a relevant quality attribute or process parameter, monitoring pH helps maintain the required product characteristics and process conditions.
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What happens when an in-process result is outside the limit?
The result should be assessed according to the approved procedure. Depending on the circumstances, this may lead to a deviation, investigation, additional assessment, or other documented action.
Are in-process checks part of GMP?
Yes. In-process controls are an important component of pharmaceutical GMP and quality assurance systems.
Do in-process checks guarantee product quality?
No. They are one part of the overall control strategy, which also includes validated processes, appropriate materials and equipment, documentation, laboratory testing, quality-system controls, and final batch assessment.
Conclusion
In-process checks in pharmaceutical manufacturing are essential for maintaining control over manufacturing operations and detecting potential quality problems at an early stage. Checks such as weight, appearance, hardness, thickness, pH, temperature, mixing conditions, fill volume, and yield help demonstrate that manufacturing is progressing within established requirements.
However, in-process checks should never be treated as isolated tests. Their effectiveness depends on validated processes, trained personnel, suitable equipment, approved procedures, accurate documentation, and appropriate investigation of abnormal results.
For QA and QC professionals, understanding the purpose and practical application of in-process checks is important for both day-to-day GMP activities and pharmaceutical quality interviews.
REFERENCE
- WHO — Good Manufacturing Practices for Pharmaceutical Products: Main Principles
WHO GMP: Main Principles - FDA — Process Validation: General Principles and Practices
FDA Process Validation Guidance - ICH Q8(R2) — Pharmaceutical Development
ICH Q8(R2) Pharmaceutical Development - ICH Q9(R1) — Quality Risk Management
ICH Q9(R1) Quality Risk Management - ICH Q10 — Pharmaceutical Quality System
ICH Q10 Pharmaceutical Quality System - WHO — WHO Expert Committee on Specifications for Pharmaceutical Preparations, Technical Report Series
WHO Technical Report Series
