Understanding ICH Photostability Testing

Light exposure can cause degradation on pharmaceutical, cosmetic, and personal care products. This material loss can lead to discoloration, potency loss, and chemical instability. To prevent these issues, global regulators use the ICH Q1B Photostability Guidelines, a standardized method for verifying that products and their packaging remain stable under UV and visible light.

What Are the ICH Photostability Guidelines?

The ICH (International Council for Harmonisation) created the Q1B Guidelines to establish a consistent way to evaluate how products react to both UV light and visible light. The goal is simple: Make sure products don’t undergo “unacceptable change” when exposed to light before they reach consumers.

This testing applies not only to the product itself but also to inner and outer packaging. If a product is sensitive to light, the packaging must provide adequate protection.

Why Photostability Testing Matters

For industries where quality is critical, light-driven degradation can lead to failures, recalls, and regulatory noncompliance. Photostability testing ensures long-term product stability and confirms that packaging provides adequate protection.

How Q-Lab Testers Perform ICH Photostability Testing

Q-Lab’s accelerated weathering instruments are widely used for ICH testing because they reliably deliver controlled, repeatable light exposure. ICH Q1B specifies two types of radiant exposure dosage:

• 200 W·hr/m² of UV light (300–400 nm) - referred to as irradiance
• 1.2 Mlx·hr/m² of Visible light (400–800 nm) - referred to as illuminance

Several factors make it complicated to establish appropriate test times to meet these targets:

1. ICH guidelines do not specify an intensity level for either step, so the user has discrection on the actual setpoint values. Higher irradiance can speed up the test, but will also cause specimen heating in xenon testing
2. Illuminance in Lux must be calculated based upon both the tester's light spectrum and the human eye's "photopic response," though Q-SUN xenon arc testers can be properly calibrated in Lux.
3. Both exposure targets are minimum requirements, so users have a choice whether to target both simultaneously, or overexpose in the UV region.

Q-Lab can provide support and guidance to address all of the factors listed above. Both xenon arc and fluorescent UV testers can be used, as described below.

Q-SUN Xenon Arc Testers

Two common approaches are used to perform ICH testing in Q-SUN xenon arc testers:

1. Procedure A – Simple & Efficient
   • A single test cycle
   • Meets the visible light requirement
   • Provides more UV exposure than required (a benefit for users seeking a harsher test)
2. Procedure B – Precise Compliance
   • Two-step programming
   • Uses optional UV-blocking filters to match both the exact UV and visible requirements. A UC20/Lux irradiance smart sensor is required to perform this method.
   • Ideal for customers who want to meet both ICH targets simultaneously without overexposure

QUV Fluorescent UV Testers

Although less common, QUV accelerated weathering testers can be used to perform ICH Guidelines testing. QUV testers use different lamp types for UV and visible light, so a multi-step exposure is needed:

• Two separate QUV testers are used (QUV/cw, QUV/se)
• Samples are exposed first to visible light, then to UV light
• This exposure type meets both the visible and UV requirements simultaneously

This approach is ideal for users who already rely on fluorescent UV technology.

Environmental Conditions: What’s Required?

Interestingly, the ICH Guidelines do not specify temperature or moisture conditions. This is unique among xenon arc standards. However, Q-Lab recommends:

• Testing near room temperature (25°C)
• Keeping conditions dry (no water spray or humidity control)
• Using a chiller in Q-SUN testers to maintain cooler test temperatures

This ensures the test focuses solely on light exposure, not heat-driven degradation.

Why This Testing Protects Your Brand

ICH photostability testing helps companies:

• Comply with global regulatory standards
• Confirm that packaging protects sensitive products
• Reduce risk of recalls or performance issues
• Deliver products consumers can trust

With accurate, repeatable light exposure, manufacturers can demonstrate that pharmaceutical products are durable under real-world lighting conditions.

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Frequently Asked Questions

Q: What is ICH Q1B photostability testing?

A: ICH Q1B is a standardized process for evaluating how products and packaging respond to UV and visible light to ensure they don’t undergo unacceptable changes before reaching consumers.

Q: Why do products need photostability testing?

A: Light can cause fading, potency loss, chemical breakdown, and packaging failures—directly impacting product safety and performance.

Q: What types of light are tested?

A: ICH Q1B requires exposure to:

• UV light (300–400 nm) - referred to as irradiance
• Visible light (400–800 nm) - referred to as illuminance

Both must meet minimum exposure levels

Q: Does packaging also need to be tested?

A: Yes. Packaging must adequately protect light-sensitive products, so both inner and outer packaging are evaluated.

Q: How does photostability testing protect brands?

A: It helps ensure regulatory compliance, verifies packaging performance, and reduces the risk of degradation-related failures, resulting in more reliable products for consumers.