NURS 2042 - Cholinergic Agents (notes)

What are cholinergic agents and what neurotransmitter do they affect?

Cholinergic agents are medications that affect the neurotransmitter acetylcholine (ACh); they inhibit, enhance, or mimic ACh at muscarinic receptors associated with the parasympathetic “rest and digest” system.

What is the primary difference between direct-acting and indirect-acting cholinergic agents?

Direct-acting agents bind directly to and activate muscarinic receptors, while indirect-acting agents increase ACh availability by inhibiting acetylcholinesterase, the enzyme that breaks down ACh.

What parasympathetic functions are regulated by direct-acting cholinergic agents?

Digestion, heart rate reduction, pupil constriction, bladder contraction, and increased urinary output.

Which three medications were covered in this lecture on cholinergic agents?

Bethanechol, Donepezil, and Pyridostigmine—each enhances cholinergic activity for specific therapeutic purposes.

What are the major therapeutic uses of direct-acting cholinergic agents?

Increasing intraocular drainage, reducing ocular pressure, causing miosis, increasing bladder tone, promoting urination, increasing GI secretions and motility, and treating postoperative/postpartum neurogenic bladder.

What are the major therapeutic indications for indirect-acting cholinergic agents?

Treating Myasthenia Gravis, Alzheimer’s disease, reversing non-depolarizing neuromuscular blockers, and managing postoperative urinary retention.

Why are cholinergic agents contraindicated in patients with GI or GU obstruction?

Because increased smooth muscle activity could worsen or rupture an obstruction, creating life-threatening complications.

Why should cholinergic agents be avoided in bradycardia, hypotension, and hyperthyroidism?

They further slow the heart, reduce blood pressure, and can worsen symptoms triggered by increased parasympathetic activity.

Why are cholinergic agents contraindicated in COPD and asthma?

Increased ACh causes bronchoconstriction and bronchospasm, worsening respiratory compromise.

Why should cholinergic agents be avoided in Parkinson’s disease?

Increased acetylcholine worsens the dopamine/ACh imbalance, intensifying Parkinson’s symptoms.

What are the most common cardiovascular side effects of cholinergic agents?

Dizziness, hypotension (most common), bradycardia, and risk of syncope from low blood pressure.

What gastrointestinal adverse effects are associated with cholinergic drugs?

Nausea, vomiting, diarrhea, and abdominal cramping due to increased GI motility and secretions.

What respiratory side effects can occur with cholinergic agents?

Bronchospasm and wheezing from increased bronchial smooth muscle activity.

What other general side effects may occur with cholinergic medications?

Increased sweating, salivation, headache, and rarely seizures from CNS effects.

How does atropine interact with cholinergic agents?

Atropine antagonizes muscarinic receptors and can worsen bradycardia or cause bronchoconstriction if used inappropriately with cholinergics.

Why must antihistamines be used cautiously with cholinergic drugs?

Many antihistamines have anticholinergic properties, causing dry mouth, urinary retention, and blurred vision, which can oppose or intensify cholinergic effects.

What is the significance of combining cholinergic drugs with other anticholinergic agents?

They may counteract each other or worsen side effects, requiring careful monitoring.

What type of drug is Bethanechol and what is its main therapeutic use?

Bethanechol is a direct-acting cholinergic agonist used to treat urinary retention by increasing bladder tone and promoting urination.

What nursing considerations are important when administering Bethanechol?

Monitor heart rate, blood pressure, and intake/output because fluid shifts from increased bladder activity can affect cardiovascular status.

What type of drug is Donepezil and what condition does it treat?

Donepezil is an acetylcholinesterase inhibitor used orally to treat Alzheimer’s disease by preventing ACh breakdown and improving cognition.

How effective is Donepezil in patients with Alzheimer’s?

About 15–30% of patients show improvement, but it is still widely prescribed due to potential cognitive benefits.

What type of drug is Pyridostigmine and what are its main uses?

Pyridostigmine is a reversible acetylcholinesterase inhibitor used for Myasthenia Gravis, reversal of tricyclic antidepressant overdose, and reversal of non-depolarizing neuromuscular blockers such as vecuronium.

What is a common adverse effect of Pyridostigmine?

Gastrointestinal upset is commonly reported due to increased GI activity.

What is the overall function of cholinergic agents in the parasympathetic nervous system?

They enhance acetylcholine activity, influencing GI, GU, ocular, respiratory, and cardiovascular functions to support parasympathetic responses.

What are the major clinical uses of cholinergic agents across all subclasses?

Treatment of urinary retention, Myasthenia Gravis, Alzheimer’s disease, reversal of neuromuscular blockers, and increasing GI motility.

What major conditions are contraindications for cholinergic therapy and why?

Parkinson’s disease, COPD, GI/GU obstruction, bradycardia, hypotension, epilepsy, and hyperthyroidism—because increased ACh can worsen symptoms or create dangerous complications.