Pyrogen testing detects bacterial toxins in drugs and vaccines that can cause fever in humans. The traditional method involves injecting rabbits with drugs to see if they develop a fever, while a newer test uses horseshoe crab blood. Pyrogenic endotoxins can cause high fever, shock, and death when injected into the bloodstream, and the Limulus Amebocyte Lysate (LAL) test is 100 times more sensitive than rabbit testing.
Pyrogen testing defines a process used by drug manufacturers to determine whether bacterial toxins are present in vaccines and drugs that could cause fever when used in humans. Determine if microbes or their metabolites are present in intravenous solutions during the manufacturing process. The most common and oldest form of pyrogen testing is to inject rabbits with drugs to determine if they are developing a fever. A newer test uses horseshoe crab blood to test for toxins.
The rabbit pyrogen test method emerged in the 1940s after some patients fell ill from intravenous drugs. Hypodermic devices at the time proved useful for delivering drugs directly into the bloodstream to patients who were unable to tolerate oral medications. While the hypodermic devices were sterile, the drugs weren’t always safe.
Patients sometimes developed high fever, chills and body aches, and some people experienced shock. Doctors did not know why this happened, often calling the condition injection fever, saline fever, or distilled water fever. Researchers later discovered that some drugs and vaccines were contaminated in manufacturing labs with pyrogenic endotoxins, potent bacteria that resist sterilization.
The human body fights exposure to bacterial toxins in the environment through the skin. When contaminated drugs are injected into the bloodstream, the toxins bypass normal defense mechanisms. The white blood cells begin to release another form of pyrogen which causes a high fever, which could lead to shock and death.
Pyrogen analysis in pharmaceutical laboratories involves heating the equipment used to ensure sterilization. The drug is injected into the ear veins of rabbits to see if a fever develops. The rectal temperatures of the experimental animals are analyzed after 30 minutes and again one to three hours later. If the animals remain fever-free, the solution is toxin-free.
The process of testing pyrogens on animals typically involves injecting several rabbits at a time over a 10-minute time frame. The dosage for each rabbit depends on body weight, age and gender. The same group of rabbits could be tested repeatedly every few days until they develop a tolerance to the drugs.
A new pyrogen testing technique is called the Limulus Amebocyte Lysate (LAL) test. Horseshoe crab blood contains high levels of toxins that occur naturally in marine life. Scientists have discovered a way to use blood to test for bacterial toxin in drugs and raw materials used to make medicines. The LAL pyrogen testing procedure may be 100 times more sensitive than rabbit testing methods. Medical devices that are implanted in humans undergo LAL testing, along with radioactive drugs and anesthesia.
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