Pyrogen Test
Pyrogen Test (Rabbit Pyrogen Test)
What a definition is not
A definition is SPEQ’s plain-language decode of how a term is used in practice, cited to the documents that define it. It is a practitioner reference, not legal or regulatory advice, it does not replace the definition in the source, and where a regulator’s wording differs the regulator’s wording governs.
An in-vivo test in which rabbits are injected with a test article and their body temperature monitored to detect pyrogenic contamination, used when the Bacterial Endotoxins Test is unsuitable — for example where the product interferes with the LAL reaction or where non-endotoxin pyrogens are a concern. Largely superseded by BET and the monocyte activation test.
The rabbit pyrogen test detects both endotoxin and non-endotoxin pyrogens (materials of microbial, fungal, or other origin that provoke a febrile response), which is why it remains a compendial fallback even though BET is faster, cheaper, and does not use animals.
The monocyte activation test, a cell-based in-vitro alternative using human blood cells, is increasingly favoured as a 3Rs-aligned replacement that, like the rabbit test but unlike BET, can detect non-endotoxin pyrogens.
A product’s formulation, matrix interference, or regulatory filing history typically dictates which of the three pyrogen-related tests — BET, monocyte activation, or rabbit pyrogen — is specified in its approved specification.
- —Detects the broader category of pyrogens, not endotoxin alone.
- —Used chiefly where BET is technically unsuitable for the product matrix.
- —Increasingly replaced by the in-vitro monocyte activation test on animal-welfare (3Rs) grounds.
- —A change from rabbit pyrogen testing to BET or MAT is a regulated specification change requiring justification.
USP <151>; Ph. Eur. 2.6.8; Ph. Eur. 2.6.30 (monocyte activation test)
Frequently asked questions
What does Pyrogen Test stand for?
Pyrogen Test stands for Pyrogen Test (Rabbit Pyrogen Test).
What is Pyrogen Test?
An in-vivo test in which rabbits are injected with a test article and their body temperature monitored to detect pyrogenic contamination, used when the Bacterial Endotoxins Test is unsuitable — for example where the product interferes with the LAL reaction or where non-endotoxin pyrogens are a concern. Largely superseded by BET and the monocyte activation test.
Which regulations cover Pyrogen Test?
USP <151>; Ph. Eur. 2.6.8; Ph. Eur. 2.6.30 (monocyte activation test)