Final answer:
Parasympathomimetic drugs mimic the action of acetylcholine at muscarinic receptors, while acetylcholinesterase inhibitors prevent the breakdown of acetylcholine enhancing its action at synapses.
Step-by-step explanation:
Drugs that mimic the action of acetylcholine; whereas drugs that inhibit the destruction of acetylcholine at receptor sites are two distinct categories impacting the cholinergic system. The first category includes muscarinic agonists or parasympathomimetic drugs which act like acetylcholine (ACh) released by the parasympathetic postganglionic fiber. They bind to muscarinic receptors and stimulate target organs as if it were the endogenous neurotransmitter.
The second category includes drugs that inhibit the enzyme acetylcholinesterase which prevents the breakdown of acetylcholine and prolongs its activity at the synaptic cleft. These drugs are generally known as acetylcholinesterase inhibitors.