What are Endotoxin Challenge Vials and Why Should Firms Use Them?

Evelyn Orona, Associate Microbiology Supervisor

Just as crucial as the sterile production of drug products is ensuring those same products are free of dangerous pyrogens - contaminants that induce febrile reactions in patients if introduced at high levels.

Relative to patient safety, the most concerning and common pyrogen is bacterial endotoxins. Pyrogens can be removed or destroyed by depyrogenation. A common method for depyrogenation is dry heat. Largely reproducible and easily controlled, dry heat depyrogenation is dependent on temperature and time to eliminate bacterial endotoxins. The depyrogenation process can be qualified and monitored with Endotoxin Challenge Vials (ECVs).

ECVs contain known concentrations of bacterial endotoxins and are available from multiple manufacturers. In addition to the physical measurements (temperature and holding time) of applicable equipment, ECVs are an excellent tool to use in confirming the effectiveness of a Dry Heat Depyrogenation cycle. Once a firm has conducted appropriate heat distribution studies in the oven being validated, ECVs can be placed in locations throughout an oven chamber, with specific focus on areas difficult to heat, known as "cold spots." Following completion of the depyrogenation cycle, the oven's ability to destroy endotoxins is measured by comparing the endotoxin concentration in test ECVs to the endotoxin concentration of untested (positive control) ECVs.

A log reduction in endotoxin concentration is calculated and used to determine whether the depyrogenation cycle is effective. A 3-log reduction is a commonly used benchmark to assess a deyprogenation process. 

However, there may be circumstances which require a higher or lower log reduction. The appropriate endotoxin log reduction for a process should be determined based on several factors including:

  • Native levels of endotoxin
  • Efficiency of depyrogenation methods
  • Patient safety

Manufacturers of ECVs generally list a 3-log reduction as the required specification. Firms can refer to USP <1228> Depyrogenation and <1228.5> Endotoxin Indicators for Depyrogenation for further guidance in determining a suitable log reduction specification for their processes.

At ARL Bio Pharma, when ECVs are received for testing, the samples are inspected and prepared per the ECV manufacturer's instructions. Using the kinetic turbidimetric assay, Endotoxin testing is performed on each ECV. 

Once results with passing quality control parameters are obtained, the Microbiologist calculates the log reduction between the test and control ECVs. All Certificate of Analyses generated include a test note indicating the log reduction achieved and whether it meets the ECVs' manufacturer's specification.

Performance of ECV testing should be scheduled periodically and is an important part of the depyrogenation process. For more information on Endotoxin Challenge Vial testing, contact ARL at 800-393-1595 or info@arlok.com.