What would be most important to have readily available for a client who is receiving an indirect-acting cholinergic agonist and develops a severe reaction?

Atropine

Explanation:

Atropine is an anticholinergic drug that inhibits the parasympathetic function that is characterized by no electrical charge.

Atropine is a drug capable of blocking the action of the parasympathetic system thanks to two pharmacodynamic characteristics that are important:

1. Its affinity for muscarinic receptors is greater than that of Ach. Therefore, Atropine will compete with Ach. endogenous for occupying these receptors and it is the Atropine who will occupy them. Atropine has a specific affinity for muscarinic receptors, it has no affinity for nicotinic or neuronal receptors, or muscle receptors.

2. Atropine only binds to muscarinic receptors, but it cannot stimulate them since it lacks intrinsic activity (intrinsic activity = 0) therefore the Atropine molecule itself has no effect on the organs innervated by the parasympathetic , the effects that we observe are a consequence of the fact that Atropine, when joining muscarinic receptors, prevents the action of Ach. in those receivers.

From this it follows that the action of anticholinergics depends primarily on the parasympathetic tone existing at the time these drugs begin to act.

This mechanism of action of Atropine is called reversible competitive antagonism. It is reversible because the antagonism disappears if we manage to increase the concentration of Ach. in the zone.