Cholinergic-Blocking Drugs Flashcards
Cholinergic-Blocking Drugs
also known as
Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)
Also known as anticholinergics, parasympatholytics, and antimuscarinic drugs
Cholinergic-Blocking Drugs Mechanism of Action
Competitive antagonists
Compete with ACh for binding at muscarinic receptors in the PSNS
As a result, ACh is unable to bind to thereceptor site and cause a cholinergic effect.
When these drugs bind to receptors, they inhibit nerve transmission at these receptors.
Cholinergic-Blocking Drugs:
Two Natural Plant Alkaloids
atropine sulphate
scopolamine hydrobromide
Cholinergic-Blocking Drugs:
Three Synthetic and semisynthetic
glycopyrrolate
oxybutynin (Ditropan®)
tolterodine (Detrol®)
Drug Effects
CVS
CNS
EYE
GI
GU
GLANDULAR
RESP
Cardiovascular
-Small doses: decreased heart rate
-Large doses: increased heart rate
Central nervous system (CNS)
-Small doses: decreased muscle rigidity and tremors
-Large dose: drowsiness, disorientation, hallucinations
Eye
-Dilated pupils (mydriasis)
-Decreased accommodation caused by paralysis of ciliary muscles (cycloplegia)
Gastrointestinal (GI)
-Relaxed smooth muscle tone of GI tract
-Decreased intestinal and gastric secretions
-Decreased motility and peristalsis
Genitourinary (GU)
Relaxed detrusor muscle
Increased constriction of internal sphincter
Result: urinary retention
Glandular
Decreased sweating
Respiratory
Decreased bronchial secretions
Anticholinergic effects
dry mouth
constipation
urinary retention
confusion
Cholinergic blockers Indications: Central Nervous System
Decreasing muscle rigidity and muscle tremors
-Parkinson’s disease (becoming less trendy)
-Drug-induced extrapyramidal reactions such as those associated with antipsychotic drugs
* involuntary movements
Cholinergic blockers Indications: Cardiovascular
Affects the heart’s conduction system
-Low doses: slow the heart rate
-High doses: block inhibitory vagal effects on sinoatrial and atrioventricular node pacemaker cells
—Results in increased heart rate
Atropine
Used primarily for ________ disorders
Diagnosis of _______________
Symptomatic ________________
Severe sinus ________ with hemodynamic compromise (advanced life support)
Cardiovascular
Used primarily for cardiovascular disorders
Diagnosis of sinus node dysfunction
Symptomatic second-degree heart block
Severe sinus bradycardia with hemodynamic compromise (advanced life support)
Cholinergic blockers Indications: Respiratory
Blocking the cholinergic stimulation of the PSNS allows unopposed action of the sympathetic nervous system.
Results
-Decreased secretions from the nose, mouth, pharynx, and bronchi
-Relaxed smooth muscles in the bronchi and bronchioles
-Decreased airway resistance
-Bronchodilation
Cholinergic blockers are used to treat:
-Exercise-induced bronchospasms
-Asthma
-Chronic obstructive pulmonary disease
Cholinergic blockers Indications: GI
The 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
GI drugs are used to treat:
-Irritable bowel disease
-GI hypersecretory states
Cholinergic blockers Indications: Genitourinary
Reflex neurogenic bladder
Incontinence
Cholinergic blockers Contraindications
Known drug allergy
Angle-closure glaucoma
Acute asthma or other respiratory distress
Myasthenia gravis
Acute cardiovascular instability
GI or GU tract obstruction (e.g., benign prostatic hyperplasia [BPH]) or illness
Cholinergic blockers AEs
Body system/adverse effects
Cardiovascular: Increased heart rate, dysrhythmias
CNS: CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium
Eye: Dilated pupils (causing blurred vision), increased intraocular pressure
GI: Decreased salivation, decreased gastric secretions, decreased motility (causing constipation)
GU: Urinary retention
Glandular: Decreased sweating
Respiratory: Decreased bronchial secretions
Toxicity and Overdose
Symptomatic and supportive therapy
Continuous electrocardiographic monitoring
Activated charcoal
Treatment of shock
Toxicity and Overdose drug to combat
Physostigmine (this is a cholinergic drug)
Cholinergic blockers Interactions
Amantadine, antihistamines, phenothiazines, digoxin
When the above drugs are given with other cholinergic-blocking drugs, cause additive cholinergic effects, resulting in increased effects
Atropine uses and contraindications
Naturally occurring antimuscarinic
Uses: bradycardia, ventricular asystole, antidote for anticholinesterase inhibitor toxicity or poisoning, and preoperatively to reduce salivation and GI secretions
Contraindications: angle-closure glaucoma, advanced hepatic and renal dysfunction, hiatal hernia associated with reflux esophagitis, intestinal atony, obstructive GI or GU conditions, and severe ulcerative colitis
Glycopyrrolate
Synthetic antimuscarinic drug
Blocks receptor sites in the autonomic nervous system that control the production of secretions
Use: preoperatively to reduce salivation and excessive secretions in the respiratory and GI tracts
Contraindications: hypersensitivity, angle-closure glaucoma, myasthenia gravis, GI or GU tract obstruction, tachycardia, myocardial ischemia, hepatic disease, ulcerative colitis, and toxic megacolon
oxybutynin (Ditropan®)
Synthetic antimuscarinic drug
Uses: overactive bladder and antispasmodic for neurogenic bladder associated with spinal cord injuries and congenital conditions such as spina bifida
Contraindications: drug allergy, urinary or gastric retention, and uncontrolled angle-closure glaucoma
Scopolamine
Uses?
Using this with _____ or _____ may increase sedation
Naturally occurring cholinergic blocker and one of the principal belladonna alkaloids
Uses: prevention of motion sickness and to help prevent postoperative, postanaesthesia nausea and vomiting
Contraindications: angle-closure glaucoma, advanced hepatic and renal dysfunction, hiatal hernia associated with reflux esophagitis, intestinal atony, obstructive GI or GU conditions, and severe ulcerative colitis
Adverse effects: drowsiness, dry mouth, and blurred vision
Using scopolamine with CNS depressants or alcohol may increase sedation.
tolterodine (Detrol®)
Muscarinic receptor blocker
Uses: urinary frequency, urgency, and urge incontinence caused by bladder (detrusor) over-activity
Newer drugs for this purpose include solifenacin (VESIcare®), darifenacin (Enablex®), trospium (Sanctura), and fesoterodine (Toviaz®).
Newer drugs are associated with a much lower incidence of dry mouth, partly because of their pharmacological specificity for the bladder as opposed to the salivary glands.
Nursing Implications
Keep in mind that these drugs block the action of ACh in the PSNS.
Assess for allergies, presence of BPH, urinary retention, glaucoma, tachycardia, myocardial infarction, heart failure, hiatal hernia, and GI or GU obstruction.
Perform baseline assessment of vital signs and systems overview.
Medications should be taken exactly as prescribed to have the maximum therapeutic effect.
Overdosing can cause life-threatening problems.
Blurred vision will cause problems with driving or operating machinery.
Patients may experience sensitivity to light and may want to wear dark glasses or sunglasses.
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.
Patients should check with the physician before taking any other medication, including over-the-counter medications.
Anticholinergics taken by older adult patients may lead to higher risk for heatstroke because of the effects on heat-regulating mechanisms.
Teach patients to limit physical exertion and to avoid high temperatures and strenuous exercise.
Emphasize the importance of adequate fluid intake.
Patients should report the following symptoms to their physician: urinary hesitancy or retention, constipation, tachycardia, palpitations, tremors, confusion, sedation, hallucinations, and decreased sweating (leading to hot, dry skin).
Monitor for therapeutic effects.
-For patients with Parkinson’s disease: fewer tremors and decreased salivation and drooling
-For patients with urological problems: improved urinary patterns, less hypermotility, increased time between voiding
Antidote for atropine overdose is
physostigmine
