Drugs Affecting the Autonomic Nervous System
ď‚— Cholinergic Agents and
Cholinergic Blocking Agents
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Cholinergic Agents ď‚— Drugs that stimulate the
parasympathetic nervous system (PSNS) ď‚— The PSNS is the opposing system to the SNS
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Cholinergic Agents Also known as ď‚— cholinergic agonists or ď‚— parasympathomimetics
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Cholinergic Agents ď‚— Mimic the effects of the PSNS neurotransmitter ď‚— Acetylcholine (ACh)
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Cholinergic Receptors Two types, determined by: ď‚— Location ď‚— Action once stimulated
Nicotinic receptors and Muscarinic receptors
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Nicotinic Receptors Located in the ganglia of both the
PSNS and SNS Named “nicotinic” because can be stimulated by the alkaloid nicotine
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Muscarinic Receptors Located postsynaptically: Smooth muscle Cardiac muscle Glands of parasympathetic fibers Effector organs of cholinergic sympathetic fibers Named “muscarinic” because can be stimulated by the
alkaloid muscarine
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Instructors may wish to insert EIC Image #57: The Sympathetic, Parasympathetic, and Somatic Nervous Systems This slide illustrates location of the nicotinic and muscarinic receptors within the PSNS.
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Adrenergic Agents: Mechanism of Action
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ď‚— Direct-acting (agonist) ď‚— Bind to cholinergic receptors, causing stimulation
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Adrenergic Agents: Mechanism of Action Indirect-acting Inhibit the enzyme “cholinesterase” Result: more ACh is available at the receptors
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Indirect-Acting Cholinergic Agents (Cholinesterase Inhibitors) Reversible Bind to cholinesterase for a period of minutes to hours Irreversible Bind to cholinesterase and form a permanent covalent
bond The body must make new cholinesterase
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Drug Effects of Cholinergic Agents Effects seen when the PSNS is stimulated. The PSNS is the “rest and digest” system.
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Drug Effects of Cholinergic Agents “SLUDGE”
Salivation Lacrimation Urinary incontinence Diarrhea Gastrointestinal cramps Emesis
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Drug Effects of Cholinergic Agents Stimulate intestine and bladder Increased gastric secretions Increased gastrointestinal motility Increased urinary frequency Stimulate pupil Constriction (miosis) Reduced intraocular pressure Increased salivation and sweating www.indiandentalacademy.com
Drug Effects of Cholinergic Agents Cardiovascular effects Decreased heart rate Vasodilation Respiratory effects Bronchial constriction, narrowed airways
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Drug Effects of Cholinergic Agents ď‚— At recommended doses, the cholinergics primarily
affect the MUSCARINIC receptors. ď‚— At high doses, cholinergics stimulate the NICOTINIC receptors.
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Drug Effects of Cholinergic Agents ď‚— DESIRED EFFECTS: from muscarinic receptor
stimulation ď‚— Many undesirable effects are due to stimulation of the nicotinic receptors
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Cholinergic Agents: Therapeutic Uses Direct-Acting Agents ď‚— Reduce intraocular pressure ď‚— Useful for glaucoma and intraocular surgery
Examples: acetylcholine, carbachol, pilocarpine Topical application due to poor oral absorption
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Cholinergic Agents: Therapeutic Uses Direct-Acting Agent—bethanechol Increases tone and motility of bladder and GI tract Relaxes sphincters in bladder and GI tract, allowing them
to empty Helpful for postsurgical atony of the bladder and GI tract Oral dose or SC injection
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Cholinergic Agents: Therapeutic Uses Indirect-Acting Agents Cause skeletal muscle contractions Used for diagnosis and treatment of
myasthenia gravis Used to reverse neuromuscular blocking agents Used to reverse anticholinergic poisoning (antidote) Examples: physostigmine, pyridostigmine
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Cholinergic Agents: Therapeutic Uses Indirect-Acting Agent—donepezil (Aricept) Used in the treatment of mild to moderate Alzheimer’s
disease. Helps to increase or maintain memory and learning capabilities.
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Cholinergic Agents: Side Effects Side effects are a result of overstimulation of the PSNS. Cardiovascular: Bradycardia, hypotension, conduction
abnormalities (AV block and cardiac arrest)
CNS: Headache, dizziness, convulsions
Gastrointestinal: Abdominal cramps, increased secretions,
nausea, vomiting
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Cholinergic Agents: Side Effects Side effects are a result of overstimulation of the PSNS. Respiratory: Increased bronchial secretions, bronchospasms
Other: Lacrimation, sweating, salivation, loss of binocular
accommodation, miosis
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Cholinergic Agents: Interactions ď‚— Anticholinergics, antihistamines, sympathomimetics ď‚— Antagonize cholinergic agents, resulting
in decreased responses
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Cholinergic Agents: Nursing Implications Keep in mind that these agents will stimulate the
PSNS and mimic the action of ACh. Assess for allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease, or coronary artery disease. Perform baseline assessment of VS and systems overview.
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Cholinergic Agents: Nursing Implications Medications should be taken as ordered
and not abruptly stopped. The doses should be spread evenly apart to optimize the effects of the medication. Overdosing can cause life-threatening problems. Patients should not adjust the dosages unless directed by the physician.
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Cholinergic Agents: Nursing Implications Encourage patients with myasthenia gravis to take
medication 30 minutes before eating to help improve chewing and swallowing. When donepezil is prescribed for Alzheimer’s disease, be honest with caregivers and patients that the drug is for management of symptoms, not for a cure. Therapeutic effects of donepezil may not occur for up to 6 weeks. www.indiandentalacademy.com
Cholinergic Agents: Nursing Implications Atropine is the antidote for cholinergics.
It should be available in the patient’s room for immediate use if needed. Patients should notify their physician if they experience muscle weakness, abdominal cramps, diarrhea, or difficulty breathing.
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Cholinergic Agents: Nursing Implications Monitor for side effects, including: Increased respiratory secretions
Abdominal cramping
Bronchospasms
Dysrhythmias
Difficulty breathing
Hypotension
Nausea and vomiting
Bradycardia
Diarrhea
Increased sweating
Increase in frequency and urgency of voiding patterns www.indiandentalacademy.com
Cholinergic Agents: Nursing Implications Monitor for therapeutic effects:
Alleviated signs and symptoms of myasthenia gravis In postoperative patients with decreased GI
peristalsis, look for:
Increased bowel sounds Passage of flatus Occurrence of bowel movements
In patients with urinary retention/hypotonic bladder,
urination should occur within 60 minutes of bethanecol administration www.indiandentalacademy.com
Cholinergic Blocking Agents ď‚— Drugs that block or inhibit the actions of
acetylcholine (ACh) in the parasympathetic nervous system (PSNS)
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Cholinergic Blocking Agents: Mechanism of Action Competitive antagonists Compete with ACh Block ACh at the muscarinic receptors
in the PSNS
As a result, ACh is unable to bind to the
receptor site and cause a cholinergic effect.
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Cholinergic Blocking Agents: Mechanism of Action ď‚— Once these drugs bind to receptors, they inhibit nerve
transmission at these receptors.
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Instructors may wish to use EIC Image #58: Site of Action of Cholinergic Blockers Within the PSNS
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Cholinergic Blocking Agents: Chemical Class Natural
Synthetic/Semisynthetic
atropine belladonna hyoscyamine scopolamine
anisotropine dicyclomine hexocyclium ipratropium oxybutynin tolterodine
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clidinium glycopyrrolate homatropine isopropamide propantheline tridihexethyl
Drug Effects of Cholinergic Blocking Agents Cardiovascular Small doses: decrease heart rate Large doses: increase heart rate CNS Small doses: decrease muscle rigidity
and tremors Large doses: drowsiness, disorientation, hallucinations
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Drug Effects of Cholinergic Blocking Agents Eye Dilated pupils (mydriasis) Decreased accommodation due to paralysis of ciliary muscles (cycloplegia) Gastrointestinal Relax smooth muscle tone of GI tract Decrease intestinal and gastric secretions Decrease motility and peristalsis
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Drug Effects of Cholinergic Blocking Agents Genitourinary Relaxed detrusor muscle Increased constriction of internal sphincter Result: urinary retention Glandular Decreased bronchial secretions, salivation,
sweating
Respiratory Decreased bronchial secretions Dilated bronchial airways www.indiandentalacademy.com
Cholinergic Blocking Agents: Therapeutic Uses CNS Decreased muscle rigidity and muscle tremors Parkinson’s disease Drug-induced extrapyramidal reactions
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Cholinergic Blocking Agents: Therapeutic Uses Cardiovascular Affect the heart’s conduction system Low doses: slow the heart rate High doses: block inhibitory vagal effects on
the SA and AV node pacemaker cells Result: increased heart rate
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Cholinergic Blocking Agents: Therapeutic Uses Atropine Used primarily for cardiovascular disorders Sinus node dysfunction Symptomatic second-degree heart block Sinus bradycardia with hemodynamic compromise
(advanced life support)
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Cholinergic Blocking Agents: Therapeutic Uses Respiratory
Blocking the cholinergic stimulation of the PSNS allows unopposed action of the SNS. Results: Decreased secretions from nose, mouth,
pharynx, bronchi
Relaxed smooth muscles in bronchi
and bronchioles
Decreased airway resistance Bronchodilation www.indiandentalacademy.com
Cholinergic Blocking Agents: Therapeutic Uses Respiratory agents are used to treat: Exercise-induced bronchospasms Chronic bronchitis Asthma Chronic obstructive pulmonary disease
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Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal PSNS controls gastric secretions and smooth muscles that produce gastric motility. Blockade of PSNS results in: Decreased secretions Relaxation of smooth muscle Decreased GI motility and peristalsis
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Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal agents are used to treat: Peptic ulcer disease Irritable bowel disease GI hypersecretory states
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Cholinergic Blocking Agents: Therapeutic Uses Genitourinary Relaxed detrusor muscles of the bladder Increased constriction of the internal sphincter Reflex neurogenic bladder Incontinence
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Cholinergic Blocking Agents: Side Effects Body System
Side/Adverse Effects
Cardiovascular
Increased heart rate, dysrhythmias
CNS
CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium
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Cholinergic Blocking Agents: Side Effects Body System
Side/Adverse Effects
Eye
Dilated pupils, decreased visual accommodation, increased intraocular pressure
Gastrointestinal
Decreased salivation, decreased gastric secretions, decreased motility
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Cholinergic Blocking Agents: Side Effects Body System
Side/Adverse Effects
Genitourinary
Urinary retention
Glandular
Decreased sweating
Respiratory
Decreased bronchial secretions
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Cholinergic Blocking Agents: Interactions ď‚— Antihistamines, phenothiazines,
tricyclic antidepressants, MAOIs ď‚— When given with cholinergic blocking agents, cause ADDITIVE cholinergic effects, resulting in increased effects
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Cholinergic Blocking Agents: Nursing Implications Keep in mind that these agents will block
the action of ACh in the PSNS. Assess for allergies, presence of BPH, glaucoma, tachycardia, MI, CHF, hiatal hernia, and GI or GU obstruction. Perform baseline assessment of VS and systems overview.
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Cholinergic Blocking Agents: Nursing Implications Medications should be taken exactly as prescribed
to have the maximum therapeutic effect.
Overdosing can cause life-threatening problems. Blurred vision may cause problems with driving
or operating machinery.
Patients may experience sensitivity to light and
may want to wear dark glasses or sunglasses.
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Cholinergic Blocking Agents: Nursing Implications When giving ophthalmic solutions, apply pressure to the
inner canthus to prevent systemic absorption.
Dry mouth may occur; can be handled by chewing gum,
frequent mouth care, and hard candy.
Check with physician before taking any other medication,
including OTC medications.
ANTIDOTE for atropine is physostigmine salicylate
(Antilirium).
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Cholinergic Blocking Agents: Nursing Implications Anticholinergics may lead to higher risk for heat
stroke due to effects on heat-regulating mechanisms. Teach patients to limit physical exertion, and avoid high temperatures and strenuous exercise. Emphasize the importance of adequate fluid and salt intake.
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Cholinergic Blocking Agents: Nursing Implications ď‚— Patients should report the following to their
physician: urinary hesitancy and/or retention, constipation, palpitations, tremors, confusion, sedation or amnesia, excessive dry mouth (especially if they have chronic lung infections or disease), or fever
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Cholinergic Agents: Nursing Implications Monitor for therapeutic effects: For patients with Parkinson’s disease:
fewer tremors and decreased salivation and drooling For patients with peptic ulcer disease: decreased abdominal pain
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Cholinergic Blocking Agents: Nursing Implications Monitor for side effects, including: Constipation Tachycardia Tremors Confusion Hallucinations Sedation Urinary retention Hot, dry skin Fever CNS depression (occurs with large doses of atropine)
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