Endotoxin

Endotoxin is a toxic lipopolysaccharide (LPS) found in the cell walls of Gram-negative bacteria. It can trigger severe immune responses, including fever or sepsis. In lab reports, contamination is measured in Endotoxin Units (EU), mainly with the Limulus amebocyte lysate (LAL) assay, to check the safety and purity of medical and injectable products.

Endotoxin levels matter on lab reports for injectable substances

Endotoxin levels on a lab report are a key sign of manufacturing hygiene. These toxins can remain in injectable substances even after successful sterilization. Because endotoxins are heat-stable, a product may be biologically sterile but still contain dangerous residues from dead bacteria that can cause systemic inflammation.

Regulators such as the FDA set strict safety thresholds for these contaminants. The general guideline caps exposure at 5 EU per kilogram of body weight per hour. A low endotoxin score on a Certificate of Analysis (COA) supports that the production process was clean and that the risk of a pyrogenic, or fever-inducing, reaction is minimized.

Common term confusions around endotoxin

• Endotoxin vs. pyrogen: All endotoxins are pyrogens, meaning fever-causing agents, but not all pyrogens are endotoxins, so the terms are not interchangeable.
• Test limitations: Endotoxin-specific tests, such as the LAL assay, detect lipopolysaccharides only and cannot identify non-endotoxin pyrogens that may also be present.
• Endotoxin vs. exotoxin: Endotoxins are structural parts of the bacterial cell wall, while exotoxins are toxic proteins actively secreted by bacteria.

Sources

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