Mastering Visual Inspection in Pharma: USP 790 & 1790 Compliance Made Easy

Introduction: Why USP 790 & 1790 Matter More Than Ever

In pharmaceutical manufacturing, especially in injectables, visual inspection is more than a quality step — it’s a regulatory requirement. The U.S. Pharmacopeia’s USP 790 Compliance standard sets clear expectations for detecting visible particulate matter in parenteral products, while USP 1790 Guidance provides detailed instructions on inspector training, qualification, and process validation.

Non-compliance isn’t just a risk to product quality — it can result in regulatory citations, recalls, and damage to brand reputation. With patient safety at stake, mastering these requirements is essential for every pharmaceutical quality team.

What is USP 790 Compliance?

USP <790> defines the requirements for ensuring injectable products are “essentially free” from visible particulate matter.

Key Points of USP 790 Compliance:

• Applies to all parenteral drug products.
• Requires 100% inspection of each unit (manual, semi-automatic, or fully automatic).
• Defects must be classified and documented.
• Acceptance Quality Level (AQL) criteria must be met.

Example:
If a vial contains visible particles like glass shards, fibers, or metal fragments, it must be rejected, documented, and investigated according to cGMP.

What is USP 1790 Guidance?

USP <1790> complements USP 790 by providing best practices for visual inspection.

It covers:

• Inspector training & qualification methods
• Probability of Detection (PoD) assessment
• Inspection booth requirements (lighting, background, ergonomics)
• Container handling techniques (swirling, inversion)
• Eye rest protocols to prevent inspector fatigue

In short: USP 1790 is the “how-to” guide for achieving USP 790 compliance.

The Role of Visual Inspection in Pharma Quality

Visual inspection ensures that products:

• Meet regulatory standards
• Are safe for patient use
• Pass stringent customer and market requirements

Common Defects Detected in Visual Inspection:

1. Particulate matter (glass, metal, fibers, hair, rubber)
2. Cosmetic defects (scratches, scuff marks)
3. Container closure defects (cracks, open seals)
4. Product-related defects (crystallization, discoloration)

Achieving USP 790 Compliance: Step-by-Step

1. Establish a Visual Inspection Program

• Define SOPs for inspection methods.
• Choose inspection type: manual, semi-automatic, or fully automatic.

2. Train & Qualify Inspectors

• Use certified defect kits (like Knapp Kit) for training.
• Follow PoD evaluation to assess detection accuracy.
• Implement refresher training at regular intervals.

3. Set Up Inspection Environment

• Black and white backgrounds for contrast.
• Lighting intensity per USP recommendations (e.g., 2000–3750 lux).
• Ergonomic setup to reduce fatigue.

4. Perform 100% Product Inspection

• Inspect every unit for visible particulate matter.
• Document rejects and conduct root cause analysis.

5. Verify & Validate Automated Systems

• Use qualification kits to ensure machine accuracy.
• Regularly challenge automated systems with known defect samples.

USP 1790 Guidance: Best Practices

Following USP 1790 ensures consistency and inspector competency.

Key Recommendations:

1. Inspector Qualification
   • Pass PoD evaluations.
   • Demonstrate detection of critical and major defects.
2. Training Tools
   • Defect library kits (glass particles, fibers, cosmetic defects).
   • Simulated defective units for realistic training.
3. Workplace Setup
   • Maintain optimal lighting and backgrounds.
   • Provide eye rest periods after 20–30 minutes of inspection.
4. Documentation & Audit Readiness
   • Maintain training records, PoD results, and machine qualification logs.
   • Be prepared to present these during regulatory audits.

Tools That Support USP 790 & 1790 Compliance

1. Knapp Kit – Visual Inspection Kits

• Manual and automatic visual inspection qualification kits.
• Certified particulate matter samples (glass, metal, fibers).
• Audit-supportive documentation and certificates.

2. Defect Library Kits

• Permanent reference set for inspector training and SOP development.

3. Probability of Detection (PoD) Evaluation Sheets

• Measure inspector accuracy and qualification status.

4. Visual Inspection Booths

• 21 CFR Part 11 compliant.
• Controlled lighting and ergonomic design.

Probability of Detection (PoD) in Visual Inspection

PoD is a critical metric in USP 1790.
It measures the percentage probability that an inspector will detect a specific defect type under defined conditions.

Example:
If an inspector detects 9 out of 10 seeded defects, their PoD score is 90%.
The higher the PoD, the greater the confidence in inspection reliability.

Challenges in Meeting USP 790 Compliance

1. Inspector Fatigue – Long inspection periods reduce accuracy.
2. Inconsistent Training – Lack of standard defect samples can cause variability.
3. Poor Lighting – Inadequate illumination affects detection rates.
4. Complex Automation Validation – Automated systems require regular qualification.

Best Practices to Ensure Compliance

• Use certified defect kits for standardized training.
• Implement ergonomic inspection booths.
• Conduct frequent PoD evaluations.
• Maintain audit-ready documentation.
• Provide annual refresher training.

Case Study: Knapp Kit in Action

A mid-sized injectable manufacturer struggled with high false rejection rates during manual inspection.
By introducing Knapp Kit for inspector training and machine qualification:

• PoD scores improved from 78% to 95%.
• Regulatory audit findings reduced to zero.
• Training time dropped by 40% due to standardized defect samples.

FAQs About USP 790 Compliance & USP 1790 Guidance

Q1: Is USP 790 mandatory?
A: Yes, for all injectable pharmaceutical products intended for the U.S. market.

Q2: How often should inspectors be requalified?
A: At least annually, or more frequently if performance issues arise.

Q3: Can automation replace manual inspection?
A: No — automated systems must still be validated and complemented by human oversight.

Q4: What is the biggest challenge in USP 1790 compliance?
A: Maintaining consistent inspector performance over time.

Q5: Are defect kits necessary?
A: Yes — they ensure standardized, reproducible training and qualification.

Conclusion: Compliance is a Continuous Process

Achieving USP 790 Compliance and following USP 1790 Guidance is not a one-time event — it’s an ongoing commitment to quality, safety, and regulatory excellence.

By investing in proper training programs, standardized defect kits, and controlled inspection environments, pharmaceutical companies can not only meet but exceed regulatory expectations.

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