Anticholinesterase

Anticholinesterase

Uses and Action

Anticholinesterase drugs are typically administered during the time when spontaneous recovery from the neuromuscular blockade is occurring so that the effect of the pharmacologic antagonist adds to the rate of spontaneous recovery from the nondepolarizing NMBD. The acetylcholinesterase inhibitors; neostigmine, pyridostigmine, and edrophonium are used to reverse the effects of nondepolarizing muscle relaxants.

Anticholinesterase drugs, such as neostigmine, accelerate the already established pattern of spontaneous recovery at the neuromuscular junction by inhibiting the activity of acetylcholinesterase increase the concentration of acetylcholine at the nerve endings by inhibiting the breakdown of acetylcholine. Increased amounts of ACh in the region of the neuromuscular junction improve the chance that the ACh molecules will bind to the cholinergic receptors. This action alters the balance of the competition between ACh and a nondepolarizing NMBD in favor of the neurotransmitter (ACh) and restores neuromuscular transmission.

Careful consideration must be given to dosing these medications. If an overdose is given, the patient may develop a cholinergic crisis. Symptoms of cholinergic crisis include bradycardia, sweating, nausea, vomiting, bronchospasm, muscle weakness, and even paralysis. Treatment of this condition includes discontinuing the use of the reversal agents and administering atropine in a dose of 10 mcg/kg IV, every 3-5 minutes, until the symptoms stop.

Contraindications to Anticholinesterase

Should not be used in patients with an active case of peritonitis, bowel obstruction, or urinary tract obstruction.

Anticholinergic must be administered with atropine or glycopyrrolate to prevent severe bradycardia or cardiac arrest. Atropine or glycopyrrolate may be combined in the same syringe as neostigmine or pyridostigmine/edrophonium. Alternatively, you can administer atropine or glycopyrrolate first. Anticholinergics should be used cautiously in patients with a history of seizures, asthma, bradycardia, and abnormal heart rhythms.

Anticholinestrase Agents

Neostigmine: Neostigmine is used to reverse the effects of nondepolarizing muscle relaxants. Onset of action is 3 minutes. Duration of action is 40-60 minutes. It must be administered with atropine or severe bradycardia/cardiac arrest may occur. Site of clearance is liver.

Dose of neostigmine: Adults/children: 0.05 mg/kg of neostigmine (maximum dose is 5 mg) mixed with 0.015 mg/kg of atropine or glycopyrrolate 0.01 mg/kg.

Pyridostigmine

It is closely related to neostigmine. Pyridostigmine has a slower onset and longer duration of action when compared to neostigmine. Onset of action is 2-5 minutes. Duration of action is 90 minutes. Sites of clearance are liver and kidneys.

Dose of pyridostigmine: Adults/children: 0.25 mg/kg of pyridostigmine (maximum dose is 30 mg) mixed with 0.015 mg/kg of atropine or 0.01 mg/kg of glycopyrrolate.