Cholinergic-Blocking Drugs

Question 1

Cholinergic-Blocking Drugs

also known as

Answer 1

Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)

Also known as anticholinergics, parasympatholytics, and antimuscarinic drugs

Question 2

Cholinergic-Blocking Drugs Mechanism of Action

Answer 2

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.

Question 3

Cholinergic-Blocking Drugs:

Two Natural Plant Alkaloids

Answer 3

atropine sulphate
scopolamine hydrobromide

Question 4

Cholinergic-Blocking Drugs:
Three Synthetic and semisynthetic

Answer 4

glycopyrrolate
oxybutynin (Ditropan®)
tolterodine (Detrol®)

Question 5

Drug Effects

CVS

CNS

EYE

GI

GU

GLANDULAR

RESP

Answer 5

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

Question 6

Anticholinergic effects

Answer 6

dry mouth
constipation
urinary retention
confusion

Question 7

Cholinergic blockers Indications: Central Nervous System

Answer 7

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

Question 8

Cholinergic blockers Indications: Cardiovascular

Answer 8

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

Question 9

Atropine

Used primarily for ________ disorders

Diagnosis of _______________

Symptomatic ________________

Severe sinus ________ with hemodynamic compromise (advanced life support)

Answer 9

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)

Question 10

Cholinergic blockers Indications: Respiratory

Answer 10

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

Question 11

Cholinergic blockers Indications: GI

Answer 11

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

Question 12

Cholinergic blockers Indications: Genitourinary

Answer 12

Reflex neurogenic bladder
Incontinence

Question 13

Cholinergic blockers Contraindications

Answer 13

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

Question 14

Cholinergic blockers AEs

Answer 14

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

Question 15

Toxicity and Overdose

Answer 15

Symptomatic and supportive therapy
Continuous electrocardiographic monitoring
Activated charcoal
Treatment of shock

Question 16

Toxicity and Overdose drug to combat

Answer 16

Physostigmine (this is a cholinergic drug)

Question 17

Cholinergic blockers Interactions

Answer 17

Amantadine, antihistamines, phenothiazines, digoxin

When the above drugs are given with other cholinergic-blocking drugs, cause additive cholinergic effects, resulting in increased effects

Question 18

Atropine uses and contraindications

Answer 18

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

Question 19

Glycopyrrolate

Answer 19

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

Question 20

oxybutynin (Ditropan®)

Answer 20

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

Question 21

Scopolamine

Uses?

Using this with _____ or _____ may increase sedation

Answer 21

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.

Question 22

tolterodine (Detrol®)

Answer 22

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.

Question 23

Nursing Implications

Answer 23

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

Question 24

Antidote for atropine overdose is

Answer 24

physostigmine