Transcript Chapter 20

CHAPTER 20
Cholinergic Drugs
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Cholinergic Drugs

Drugs that stimulate the parasympathetic
nervous system (PSNS)

The PSNS is the opposing system to
the SNS
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
2
Cholinergic Drugs (cont’d)


Also known as cholinergic agonists or
parasympathomimetics
Mimic effects of the PSNS neurotransmitter
acetylcholine (ACh)
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
3
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
4
Cholinergic Receptors

Two types, determined by:




Location
Action once stimulated
Nicotinic receptors
Muscarinic receptors
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
5
Nicotinic Receptors


Located in the ganglia of both the
PSNS and SNS
Named nicotinic because they can be
stimulated by the alkaloid nicotine
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
6
Muscarinic Receptors

Located postsynaptically in the effector
organs of the PSNS




Smooth muscle
Cardiac muscle
Glands
Named muscarinic because they can be
stimulated by the alkaloid muscarine
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
7
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
8
Mechanism of Action

Direct-acting cholinergic agonists


Bind to cholinergic receptors, activating them
Indirect-acting cholinergic agonists


Inhibit the enzyme acetylcholinesterase, which
breaks down ACh
Results in more ACh available at the receptors
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
9
Indirect-Acting
(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 to break
these bonds
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
10
Drug Effects


Effects seen when PSNS is stimulated
The PSNS is the “rest and digest” system
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
11
Drug Effects (cont’d)

SLUDGE acronym

Salivation
 Lacrimation
 Urinary incontinence
 Diarrhea
 Gastrointestinal cramps
 Emesis
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
12
Drug Effects (cont’d)

Stimulate intestine and bladder




Increased gastric secretions
Increased gastrointestinal motility
Increased urinary frequency
Stimulate pupils

Constriction (miosis)
 Reduced intraocular pressure

Increased salivation and sweating
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
13
Drug Effects (cont’d)

Cardiovascular effects



Decreased heart rate
Vasodilation
Respiratory effects

Bronchial constriction, narrowed airways
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
14
Drug Effects (cont’d)


At recommended doses, cholinergics
primarily affect muscarinic receptors
At high doses, cholinergics stimulate nicotinic
receptors
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
15
Drug Effects (cont’d)


Desired effects are from muscarinic receptor
stimulation
Many undesirable effects are caused by
stimulation of nicotinic receptors
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
16
Indications

Direct-acting drugs



Reduce intraocular pressure
Useful for glaucoma and intraocular surgery
• Acetylcholine
• Carbachol
• Pilocarpine
Topical application because of poor oral
absorption
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
17
Indications (cont’d)

Direct-acting drug—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
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
18
Indications (cont’d)

Indirect-acting drugs

Cause skeletal muscle contractions
 Used for diagnosis and treatment of
myasthenia gravis
 Used to reverse neuromuscular blocking drugs
 Used to reverse anticholinergic poisoning
(antidote)
• Examples: physostigmine, pyridostigmine
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
19
Indications (cont’d)

Indirect-acting drug—cevimeline (Evoxac)

Used to treat xerostomia (dry mouth) resulting
from Sjögren’s syndrome
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
20
Indications (cont’d)

Indirect-acting anticholinesterase drugs

Used for treatment of mild to moderate
Alzheimer’s disease
• donepezil (Aricept)
• tacrine (Cognex)
• galantamine (Razadyne)
• rivastigmine (Exelon)
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
21
Indications (cont’d)

memantine (Namenda)


Not a cholinergic drug
Also used in the treatment of Alzheimer’s disease
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
22
Adverse Effects


Adverse effects are a result of overstimulation of
the PSNS
Cardiovascular


CNS


Bradycardia, hypotension, conduction abnormalities
(AV block and cardiac arrest)
Headache, dizziness, convulsions
Gastrointestinal

Abdominal cramps, increased secretions, nausea,
vomiting
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
23
Adverse Effects (cont’d)

Respiratory


Increased bronchial secretions, bronchospasms
Other

Lacrimation, sweating, salivation, loss of binocular
accommodation, miosis
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
24
Interactions

Anticholinergics, antihistamines,
sympathomimetics


Antagonize cholinergic drugs, resulting in
decreased responses
Other cholinergic drugs

Additive effects
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
25
Herbal Products: Gingko

Common uses





Organic brain syndrome
Vertigo
Tinnitus
May cause GI upset, headache, bleeding
Potential interactions

Aspirin
 NSAIDs
 Anticoagulants
 Anticonvulsants
 Others
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
26
Nursing Implications



Note that these drugs 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 vital signs
and systems overview
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
27
Nursing Implications (cont’d)



Medications should be taken as ordered
and not abruptly stopped
Doses should be spread evenly apart
to optimize the effects of the medication
Overdosing can cause life-threatening
problems. Patients should not adjust dosages
unless directed by their physician
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
28
Nursing Implications (cont’d)



Encourage patients with myasthenia gravis to
take medication 30 minutes before eating to
help improve chewing and swallowing
When cholinergic drugs are prescribed for
Alzheimer’s disease, be honest with
caregivers and patients that the drugs are for
management of symptoms (not a cure)
Therapeutic effects of anti-Alzheimer’s drugs
may not occur for up to 6 weeks
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
29
Nursing Implications (cont’d)


Atropine is the antidote for cholinergics, and 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
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
30
Nursing Implications (cont’d)

Monitor for therapeutic effects

Alleviated signs and symptoms of myasthenia
gravis

In postoperative patients with decreased GI
peristalsis, monitor for:
• Increased bowel sounds
• Passage of flatus
• Occurrence of bowel movements
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
31
Nursing Implications (cont’d)

Monitor for therapeutic effects


In patients with urinary retention/hypotonic
bladder, urination should occur within 60 minutes
of bethanechol administration
Also monitor for adverse effects
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
32