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  • Image not available.The primary clinical use of cholinesterase inhibitors, also called anticholinesterases, is to reverse nondepolarizing muscle blockade.
  • Image not available.Acetylcholine is the neurotransmitter for the entire parasympathetic nervous system (parasympathetic ganglions and effector cells), parts of the sympathetic nervous system (sympathetic ganglions, adrenal medulla, and sweat glands), some neurons in the central nervous system, and somatic nerves innervating skeletal muscle.
  • Image not available.Neuromuscular transmission is blocked when nondepolarizing muscle relaxants compete with acetylcholine to bind to nicotinic cholinergic receptors. The cholinesterase inhibitors indirectly increase the amount of acetylcholine available to compete with the nondepolarizing agent, thereby reestablishing neuromuscular transmission.
  • Image not available.In excessive doses, acetylcholinesterase inhibitors can paradoxically potentiate a nondepolarizing neuromuscular blockade. In addition, these drugs prolong the depolarization blockade of succinylcholine.
  • Image not available.Any prolongation of action of a nondepolarizing muscle relaxant from renal or hepatic insufficiency will probably be accompanied by a corresponding increase in the duration of action of a cholinesterase inhibitor.
  • Image not available.The time required to fully reverse a nondepolarizing block depends on several factors, including the choice and dose of cholinesterase inhibitor administered, the muscle relaxant being antagonized, and the extent of the blockade before reversal.
  • Image not available.A reversal agent should be routinely given to patients who have received nondepolarizing muscle relaxants unless full reversal can be demonstrated or the postoperative plan includes continued intubation and ventilation.
  • Image not available.In monitoring a patient’s recovery from neuromuscular blockade, the suggested end points are sustained tetanus for 5 s in response to a 100-Hz stimulus in anesthetized patients or sustained head lift in awake patients. If neither of these end points is achieved, the patient should remain intubated and ventilation should be continued.

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Image not available.The primary clinical use of cholinesterase inhibitors, also called anticholinesterases, is to reverse nondepolarizing muscle blockade. However, this group of drugs has effects on cholinergic receptors beyond the neuromuscular end plate. This chapter reviews cholinergic pharmacology, explores the mechanisms of acetylcholinesterase inhibition, and presents the clinical pharmacology of commonly used cholinesterase inhibitors (neostigmine, edrophonium, pyridostigmine, and physostigmine).

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Cholinergic Pharmacology: Introduction

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The term cholinergic refers to the effects of the neurotransmitter acetylcholine, as opposed to the adrenergic effects of noradrenaline (norepinephrine). Acetylcholine is synthesized in the nerve terminal by the enzyme choline acetyltransferase, which catalyzes the reaction between acetylcoenzyme A and choline (Figure 10–1). After its release, acetylcholine is rapidly hydrolyzed by acetylcholinesterase (true cholinesterase) into acetate and choline.

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Figure 10–1.
Graphic Jump Location

The synthesis and hydrolysis of acetylcholine.

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Image not available.Acetylcholine is the neurotransmitter for the entire parasympathetic nervous system (parasympathetic ganglions and effector cells), parts of the sympathetic nervous system (sympathetic ganglions, adrenal medulla, and sweat glands), some neurons in the central nervous system, and somatic nerves innervating skeletal muscle (Figure 10–2).

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Figure 10–2. 
Graphic Jump Location

The parasympathetic nervous system uses acetylcholine as a preganglionic and postganglionic ...

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