Thank you for the information scabdraggr but I'm really specifically asking about treatments that target areas outside the gastrointestinal tract, or was trying to. My use of language is still not as accurate as it needs to be.
Wiki on Fenbendazole states that toxicity has been reported from its use in many species, associated with bone marrow suppression..., intestinal crypt cell necrosis and villi sloughing, whatever that is.