Cholinergic Drugs Study Notes

When you reach the end of this chapter, you will be able to:
1. Briefly review the functions of the autonomic nervous system and the impact of the parasympathetic division.
2. List the various drugs classified as cholinergic agonists (also called parasympathomimetics).
3. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, drug interactions, cautions, contraindications, dosages, routes of administration, and any antidotal management for the various cholinergic agonists (or parasympathomimetics).
4. Develop a nursing care plan that includes all phases of the nursing process for patients taking cholinergic agonists.

Acetylcholine: The neurotransmitter responsible for the transmission of nerve impulses to effector cells in the parasympathetic nervous system.
Acetylcholinesterase: The enzyme responsible for the breakdown of acetylcholine.
Alzheimer’s disease: A disease of the brain characterized by progressive mental deterioration manifested by confusion, disorientation, and loss of memory, ability to calculate, and visual-spatial orientation.
Atony: A lack of normal muscle tone.
Cholinergic crisis: Severe muscle weakness and respiratory paralysis due to excessive acetylcholine; often seen in patients with myasthenia gravis as an adverse effect of drugs used to treat the disorder.
Cholinergic receptor: A nerve receptor stimulated by acetylcholine.
Miosis: The contraction of the pupil.
Muscarinic receptors: Cholinergic receptors located postsynaptically in the effector organs such as smooth muscle, cardiac muscle, and glands supplied by parasympathetic fibers.
Nicotinic receptors: Cholinergic receptors located in the ganglia of both the parasympathetic nervous system and the sympathetic nervous system; they can be stimulated by nicotine.
Parasympathomimetics: Drugs that mimic the actions of the parasympathetic nervous system, also referred to as cholinergic agonist drugs.

Cholinergic drugs are substances that stimulate the parasympathetic nervous system.
There are two types of cholinergic receptors: nicotinic and muscarinic.
- Nicotinic receptors are located in the ganglia of both the PNS and SNS, stimulated by nicotine.
- Muscarinic receptors are located in effector organs supplied by parasympathetic fibers, stimulated by muscarine.
Cholinergic agonists can stimulate cholinergic receptors directly or indirectly:
- Direct-acting cholinergic agonists bind directly to cholinergic receptors and activate them.
- Indirect-acting cholinergic agonists stimulate postsynaptic release of acetylcholine at the receptor site and inhibit acetylcholinesterase, increasing acetylcholine concentration at receptor sites.

Bethanechol (Urecholine): Used for urinary retention.
Carbachol (Carboptic): Used topically for ocular surgery and glaucoma.
Cevimeline (Evoxac): Used for dry mouth from Sjögren’s syndrome.
Pilocarpine (Salagen, Pilocar): Used for glaucoma, helps decrease intraocular pressure.
Succinylcholine (Anectine): Used as a neuromuscular blocker in general anesthesia.

Donepezil (Aricept): Used for Alzheimer’s dementia.
Echothiophate (Phospholine Iodide): Used in glaucoma.
Edrophonium (Tensilon): Used to diagnose myasthenia gravis.
Galantamine (Razadyne): Used for Alzheimer’s disease.
Neostigmine (Prostigmin): Used for myasthenia gravis and reversing blockade.
Physostigmine (Antilirium): Antidote for anticholinergic poisoning.
Pyridostigmine (Mestinon): Used for myasthenia gravis.
Rivastigmine (Exelon): Used for Alzheimer’s dementia.

Once acetylcholine binds to its receptor, it allows sodium and calcium to flow into the cell, causing depolarization and stimulation of the effector organ.
Cholinergic drugs primarily target the gastrointestinal (GI) tract, bladder, and eye.

Body Tissue/Organ	Muscarinic Effects	Nicotinic Effects
Bronchi (lungs)	Increased secretions; constriction	None
Cardiovascular	Blood vessels dilation; heart rate slowed	Increased
Eye	Miosis; decreased accommodation	Miosis
Gastrointestinal	Increased tone and motility	Increased tone
Genitourinary	Increased tone; decreased sphincter tone	Increased tone
Salivary Glands	Increased secretions	None
Skeletal Muscle	None	Increased contraction

Direct-Acting Drugs: Carbachol and pilocarpine for glaucoma; bethanechol for bladder atony; cevimeline for dry mouth; succinylcholine as a neuromuscular blocker.
Indirect-Acting Drugs: Increasing acetylcholine concentrations beneficial in Alzheimer's disease and myasthenia gravis treatment.

Known drug allergy, GI obstruction, bradycardia, cardiac impulse conduction defects, hyperthyroidism, epilepsy, hypotension, chronic obstructive pulmonary disease, Parkinson's disease.
Special consideration for patients with dementia or fluctuating neurological status.

Adverse effects may include effects from overstimulation of the PNS:
- Bradycardia or tachycardia, hypotension or hypertension, syncope, gastrointestinal upset, diarrhea, salivation, increased bronchial secretions.

Cholinergic Crisis: Symptoms include circulatory collapse, hypotension, bloody diarrhea, shock, and cardiac arrest.
Use of atropine (anticholinergic) to reverse effects; epinephrine may assist with severe cardiovascular reactions.
Mnemonic SLUDGE: Salivation, Lacrimation, Urinary incontinence, Diarrhea, Gastrointestinal cramps, Emesis.

Conduct a thorough assessment of patient history and physical examination focusing on:
- Vital Signs, particularly blood pressure, looking for orthostatic hypotension,
- Nail color, temperature, and peripheral pulses to assess perfusion.
- Evaluate risk factors that may exacerbate cholinergic effects.

Educate about expected effects and potential adverse reactions.
Encourage patients to maintain a journal documenting any side effects experienced during therapy.
Ensure understanding of the importance of reporting unusual symptoms.

Monitor efficacy through vital signs, symptom reduction, and adverse effects. Adjust care based on patient response and document the findings.

Comprehensive understanding and careful monitoring of cholinergic drugs are essential for effective patient management and safety in clinical settings. Recommendations include close patient education and observation to ensure optimal therapeutic outcomes.