How does the toxicity of endotoxin change when radiopharmaceuticals are administered into the cerebrospinal fluid (CSF) compared to systematically administered preparations?

When radiopharmaceuticals are administered into the cerebrospinal fluid (CSF), the toxicity of endotoxins significantly increases compared to systematically administered preparations. This heightened toxicity occurs because the CSF is a direct pathway to the central nervous system (CNS), which is particularly sensitive to toxins. The blood-brain barrier offers some level of protection against systemic exposure, but once substances enter the CSF, they can affect the CNS directly without the filter of the barrier.

In the case of endotoxins, which are components of bacterial cell walls, their effects can be particularly harmful in the CNS. They can lead to inflammation, neurological damage, or other severe reactions. Therefore, the route of administration is crucial; when endotoxins are delivered directly into the CSF, their potential for harm is much higher than when their introduction is via the bloodstream.

This understanding highlights the significance of careful monitoring and quality control measures when dealing with radiopharmaceuticals and potential contaminants like endotoxins, especially in sensitive areas like the CNS.