Pyrogens are lipopolysaccharides, in which the lipid part is pyrogenic in nature and the polysaccharide part increases the solubility of the pyrogen. Pyrogens are fever-inducing substances and are the products of metabolism of bacteria and viruses. However, it is the gram-negative bacteria that produce the most potent pyrogen. Pyrogen contamination can occur due to environmental factors, and through contaminated solute, solvent, apparatus, and container. The human body is capable of fighting the bacterial toxins it is exposed to in the environment through the skin. However, when contaminated drugs are injected into the bloodstream, the toxins bypass normal defense mechanisms. In such a situation, the white blood cells present in the body start releasing another form of pyrogen that causes high fever, which in certain cases may lead to shock and death. Rise in body temperature, chills, body aches, rise in arterial blood pressure, and cutaneous vasoconstriction are some of the reactions caused in the human body following the injection of harmful pyrogens. Pharmaceutical companies use pyrogen testing to determine the presence of bacterial toxins in medical and veterinary products.
This process helps to detect the presence of microbes or their metabolites in intravenous solutions during manufacturing operations. The most common and oldest form of pyrogen testing is injecting drugs into rabbits. During this process, the substance is injected into the rabbit’s ear to determine if the fever occurs. The rabbit pyrogen test is commonly conducted to detect the possibility of pyrogen contamination in injectable pharmaceuticals. However, the rabbit pyrogen test has some limitations. Limulus Amebocyte Lysate (LAL) test, a bacterial endotoxin test, is also used to detect pyrogens. This test is carried out on pharmaceutical products used in parenteral dosage form, blood products and plasma fractions, vaccines, nebulizers used in respiratory therapy, and for the validation of dry heat sterilization. However, LAL test is more advantageous than the rabbit pyrogen test as it is less time consuming, more sensitive, less expensive, and easier to perform.
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