INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiadentalacademy.com
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Cholinergic Agents and Cholinergic Blocking Agents
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Drugs that stimulate the parasympathetic nervous system (PSNS) The PSNS is the opposing system to the SNS
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Also known as ď ˝ cholinergic agonists or ď ˝ parasympathomimetics
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Mimic the effects of the PSNS neurotransmitter Acetylcholine (ACh)
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Two types, determined by: ď ˝ ď ˝
Location Action once stimulated
Nicotinic receptors and Muscarinic receptors
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Located in the ganglia of both the PSNS and SNS Named “nicotinic” because can be stimulated by the alkaloid nicotine
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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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This slide illustrates location of the nicotinic and muscarinic receptors within the PSNS.
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Lisa L. Lisa L. HHS: HHS: Hernandez: HHS: Hernandez: HHS: IsIsthere therecopy copy missing missingatatthe the end? end?Inhibiting Inhibiting what? ď ˝ Direct-acting what?
(agonist)
â—Ś Bind to cholinergic receptors, causing stimulation
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Indirect-acting
◦ Inhibit the enzyme “cholinesterase” Result: more ACh is available at the receptors
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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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Effects seen when the PSNS is stimulated. The PSNS is the “rest and digest” system.
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“SLUDGE”
Salivation Lacrimation Urinary incontinence Diarrhea Gastrointestinal cramps Emesis
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Stimulate intestine and bladder ◦ Increased gastric secretions ◦ Increased gastrointestinal motility ◦ Increased urinary frequency
Stimulate pupil
◦ Constriction (miosis) ◦ Reduced intraocular pressure
Increased salivation and sweating
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Cardiovascular effects ◦ Decreased heart rate ◦ Vasodilation
Respiratory effects
◦ Bronchial constriction, narrowed airways
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At recommended doses, the cholinergics primarily affect the MUSCARINIC receptors. At high doses, cholinergics stimulate the NICOTINIC receptors.
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DESIRED EFFECTS: from muscarinic receptor stimulation Many undesirable effects are due to stimulation of the nicotinic receptors
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Direct-Acting Agents ď ˝ ď ˝
Reduce intraocular pressure Useful for glaucoma and intraocular surgery Examples: acetylcholine, carbachol, pilocarpine Topical application due to poor oral absorption
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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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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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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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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 www.indiandentalacademy.com
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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Anticholinergics, antihistamines, sympathomimetics Antagonize cholinergic agents, resulting in decreased responses
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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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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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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.
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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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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
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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
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Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)
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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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Once these drugs bind to receptors, they inhibit nerve transmission at these receptors.
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Natural
atropine belladonna hyoscyamine scopolamine
Synthetic/Semisynthetic anisotropine dicyclomine hexocyclium ipratropium oxybutynin tolterodine
clidinium glycopyrrolate homatropine isopropamide propantheline tridihexethyl
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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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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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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
CNS
Decreased muscle rigidity and muscle tremors Parkinson’s disease Drug-induced extrapyramidal reactions
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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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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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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
Respiratory agents are used to treat:
Exercise-induced bronchospasms Chronic bronchitis Asthma Chronic obstructive pulmonary disease
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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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Gastrointestinal agents are used to treat:
Peptic ulcer disease Irritable bowel disease GI hypersecretory states
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Genitourinary
Relaxed detrusor muscles of the bladder Increased constriction of the internal sphincter Reflex neurogenic bladder Incontinence
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Body System
Side/Adverse Effects
Cardiovascular
Increased heart rate, dysrhythmias
CNS
CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium
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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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Body System
Side/Adverse Effects
Genitourinary
Urinary retention
Glandular
Decreased sweating
Respiratory
Decreased bronchial secretions
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Antihistamines, phenothiazines, tricyclic antidepressants, MAOIs When given with cholinergic blocking agents, cause ADDITIVE cholinergic effects, resulting in increased effects
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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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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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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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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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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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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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Monitor for side effects, including: Constipation Tremors Hallucinations Urinary retention Fever CNS depression (occurs with
Tachycardia Confusion Sedation Hot, dry skin
large doses of atropine)
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