Which of the following is NOT classified as a physiological effect category of toxins?

Antitoxins are not classified as a physiological effect category of toxins because they function differently from the other options listed. Whereas neurotoxins, enterotoxins, and cytotoxins are types of toxins that directly harm cells, tissues, or systems in the body, antitoxins serve as defensive agents. They are antibodies that neutralize toxins by binding to them and preventing their harmful effects. This crucial distinction places antitoxins in a separate role within the context of toxin-related physiology.

In contrast, neurotoxins affect the nervous system, enterotoxins target the gastrointestinal tract, and cytotoxins cause damage to cells directly. Hence, antitoxins do not fit the classification as they do not produce a physiological effect in the same manner as the other types of toxins. Their purpose is to counteract the effects of harmful toxins rather than cause damage themselves.