ICH Q3B and Q3C: Impurities and Solvent Residues in Drugs

What Is ICH Q3B? Degradation Products and Qualification Thresholds

ICH Q3B and Q3C: Guidance on Impurities and Solvent Residues in New Drug Products

One of the most critical aspects of quality assurance in the drug development process is keeping undesirable components—that is, impurities—in the product under control. The ICH (International Council for Harmonisation) has published a series of Q3 guidelines to establish globally harmonized standards in this area. In this article, we take a detailed look at the Q3B guideline, which addresses degradation products in new drug products, and the Q3C guideline, which regulates solvents remaining from the manufacturing process.

What Is ICH Q3B?

ICH Q3B (R2)—Impurities in New Drug Products—covers impurities formed in the finished drug product (tablet, capsule, solution, etc.), not the active ingredient. These impurities generally arise in two ways:

• Decomposition products: Compounds formed as a result of the active ingredient breaking down over time due to the effects of storage, light, moisture, or temperature
• Interaction products: Compounds formed as a result of reactions between the active ingredient and excipients or packaging materials

Q3B complements Q3A (active ingredient impurities). Together, the two guidelines comprehensively address the impurity profile of a drug at both the raw material and finished product stages.

Key Principles of Q3B

1. Reporting, Identification, and Characterization Thresholds

The guideline defines a three-tiered threshold system based on the daily dose:

• Reporting threshold: Any impurity above this level must be reported in the analytical results.
• Identification threshold: The chemical structure of impurities above this level must be determined.
• Characterization threshold: Impurities above this level must be evaluated for safety.

The thresholds vary depending on the drug’s maximum daily dose. The higher the dose, the lower the thresholds are set.

2. Relationship to Stability Studies

Q3B is closely linked to the ICH Q1A stability guideline. Stability studies conducted throughout the shelf life serve as the primary data source for monitoring degradation products that may form in the product over time.

3. Characterization Approaches

For an impurity to be considered safe, it must have been evaluated in the toxicological literature or supported by specific toxicology studies.

What Is ICH Q3C?

The ICH Q3C — Impurities: Residual Solvents guideline addresses organic solvents used in drug manufacturing that may remain in trace amounts in the product. The guideline has currently reached the Q3C (R9) revision.

Solvent Classification

Permissible Daily Exposure (PDE)

PDE refers to the amount of solvent to which a patient can be safely exposed on a daily basis:

PDE (mg/day) = NOAEL or LOAEL × 50 / (F1 × F2 × F3 × F4 × F5)

Here, F1–F5 represent uncertainty factors such as differences in animal species, study duration, and severity of toxicity.

Why Are Q3B and Q3C Evaluated Together?

Both guidelines are components of the impurity control strategy that defines a drug product’s final quality and safety profile:

• Q3A → Impurities in the active ingredient
• Q3B → Degradation/interaction products in the finished product
• Q3C → Solvents remaining from the manufacturing process
• Q3D → Elemental impurities

Points to Consider in Practice

1. The sensitivity of analytical methods must be sufficient to detect levels below the threshold values.
2. Accelerated degradation studies help in the early identification of potential degradation products.
3. Class 3 solvents should be preferred whenever possible when selecting solvents.
4. Compliance with current PDE values is also expected for licensed products.

The ICH Q3B and Q3C guidelines ensure that unwanted chemical components to which patients are exposed are controlled within a scientifically based and globally harmonized framework. Proper implementation of these guidelines not only accelerates the approval process for marketing authorization applications but also contributes to safeguarding patient safety.

For all your inquiries, contact us.
For the latest news and updates about our services, you can follow us on LinkedIn.
To stay updated on our latest blog posts, follow our Instagram account.