USP General Chapter 85 (revision 15)
Old revision·09:24, 1 Jun 2025·SeeAlsoSelma
| USP General Chapter 85Compendial chapter | |
|---|---|
| Title | Bacterial Endotoxins Test |
| Status | General chapter below 1000, and therefore mandatory where referenced |
| Methods | Gel-clot, turbidimetric, chromogenic |
| Topic infobox · conventions | |
USP General Chapter 85, titled Bacterial Endotoxins Test, is the chapter of the United States Pharmacopeia that prescribes how endotoxin is measured, how the limit for a product is calculated, and how method suitability is demonstrated.[1]
Chapters numbered below 1000 are mandatory where a monograph or another applicable requirement references them; chapters numbered 1000 and above are informational. This distinction matters when reading a certificate that cites a chapter, because citing an informational chapter is a different kind of claim from citing a mandatory one.[2]
The chapter is harmonised in substance with the corresponding chapters of the European and Japanese pharmacopoeias, so a determination described as conforming to one is broadly comparable with one conforming to another.[1]
What the chapter specifies
[edit]The chapter defines the three permitted techniques — gel-clot, turbidimetric and chromogenic — and treats the gel-clot method as the referee method where results conflict. It specifies preparation of the standard endotoxin, the confirmation of lysate sensitivity, and the inhibition and enhancement testing that establishes whether a particular sample matrix interferes with the reaction.[1]
It also specifies how the endotoxin limit for a product is calculated. The limit derives from the threshold pyrogenic dose and the maximum human dose per kilogram per hour, so a limit expressed per milligram of substance depends on the dose that substance is given at. Two products with the same per-milligram figure may sit on opposite sides of their respective limits.
The maximum valid dilution follows from the limit and the lysate sensitivity, and constrains how far a sample may be diluted to overcome interference. Dilution is the usual remedy for interference, and the chapter bounds it so that dilution cannot be used to dilute the endotoxin below detection as well.[1]
Reading a citation on a certificate
[edit]A certificate stating "endotoxin: <0.5 EU/mg, USP <85>" is asserting that the determination followed the chapter. The fields that make that assertion checkable are the method variant used, the lysate sensitivity, and whether inhibition and enhancement testing was performed on this matrix.[1]
| Field | Why it matters |
|---|---|
| Method variant | Gel-clot gives a limit result, not a number |
| Lysate sensitivity | Sets the achievable detection limit |
| Interference testing | Without it, a low result may be inhibition |
| Basis of normalisation | Per mg of what — substance, or vial contents? |
A numeric result reported from a gel-clot determination is a category error, since the gel-clot method reports whether a clot formed at a dilution rather than a concentration. Certificates showing a number attributed to a gel-clot method are internally inconsistent — see Test report forgery for the general treatment of internal consistency.[3] Where a non-endotoxin pyrogen is at issue, a different chapter applies entirely.[4]
See also
References
- ^ a b c d e United States Pharmacopeia, General Chapter <85>, Bacterial Endotoxins Test.
- ^ United States Pharmacopeia, General Notices and Requirements, section 3 (conformance to standards) and the numbering convention for general chapters.
- ^ United States Pharmacopeia, General Chapter <1503>, Quality Attributes of Synthetic Peptide Drug Substances.
- ^ United States Pharmacopeia, General Chapter <151>, Pyrogen Test.