Enzyme and receptor-mediated mechanisms
Acute toxicity usually occurs with alterations of essential metabolic pathways or interaction with important proteins or receptors. Enzyme interference is well-illustrated by nerve gases, which act similarly to neostigmine (an acetylcholinesterase inhibitor).
Drug interaction with important proteins can also have serious consequences. Certain drugs (metoclopramide, primaquine) can oxidise haemoglobin, which makes oxygen binding impossible.