04 cholinergic blockers upd9/ dental implant courses by Indian dental academy

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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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