Irreversible antagonism

Antagonism Irreversible (non-equilibrium) competitive Equilibrium competitive Equilibrium competitive... 

In systems where there is insufficient time for the agonist, antagonist, and receptor to equilibrate according to mass action slow-offset antagonists can produce essentially irreversible occlusion of a portion of the receptor population. This can result in insurmountable antagonism. 

Folate supplements will rectify the megaloblastic anemia of vitamin Bj2 deficiency but may hasten the development of the (irreversible) nerve damage found in B,2 deficiency. There is also antagonism between fohc acid and the anticonvulsants used in the treatment of epilepsy. 

J. J. Tyson and B. Novak, Regulation of the eukaryotic cell cycle Molecular antagonism, hysteresis, and irreversible transitions. J. Theor. Biol. 210, 249-263 (2001). 

The toxin acts on nerves to block transmissions to the muscle by increasing the permeability of membranes to sodium ions. It is specifically antagonized by tetro-dotoxin (Fig. 30-16). Batrachotoxin alkaloids are present also in certain birds.3303 Some echinoderms make powerful steroid toxins such as holothuiin A (Fig. 22-12), a surface active agent that causes irreversible destruction of the excitability of neuromuscular tissues. The common toad produces in its skin steroid toxins such as bufotoxin (Fig. 22-12), which are sufficiently powerful to teach a dog to leave toads alone. 

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