week 4 - Cholinergic Agents Flashcards
Cholinergic Agents: Definition
Drugs that stimulate the parasympathetic nervous system (PSNS)
The PSNS is the opposing system to the SNS
Rest and Digest
• Also known as cholinergic agonists or parasympathomimetics
Mimic the effects of the PSNS neurotransmitter: acetylcholine (ACh)
Cholinergic Receptors
• Two types of cholinergic receptors which are determined by:
=Location
=Action once stimulated
*** “Nicotinic receptors” and “muscarinic receptors”
Cholinergic Agents
Mimic the effects of acetylcholine by stimulating the receptors either directly or indirectly
Direct Acting Agents: act as agonists at the receptor
Bind to cholinergic receptors and activate them (causes stimulation)
Indirect Acting Agents: act by making more acetylcholine available at the receptor sites
Therefore allowing more acetylcholine to bind and stimulate the receptors
Nicotinic Receptors
Located in the ganglia of both the PSNS and SNS
Named “nicotinic” because they can be stimulated by the alkaloid nicotine
(stimulation of the smooth muscle and gland secretions)
Muscarinic Receptors
Located postsynaptically in:
Smooth muscle
Cardiac muscle
Glands of the parasympathetic fibers
Effector organs of cholinergic sympathetic fibers
Named “muscarinic” because they can be stimulated by the alkaloid muscarine
Drug Effects
Effects seen when the PSNS is stimulated
The PSNS is the “rest and digest” system
—Have few therapeutic uses because of their numerous side effects
Used after anesthesia to stimulate smooth muscle of the bowel or urinary tract
Glaucoma to reduce increased intra ocular pressure
Ocular surgery
Indications
Glaucoma: reduces IOP
Ocular surgery: miosis (constriction)
Post anaesthetic: stimulates GI system and the GU system (relaxation)
Reversal of anticholinergic poisoning: physostigmine direct antidote
Reversal of neuroblocking agents: neostigmine
Alzheimer’s Disease: increases acetylcholine (Ach)
Myasthenia Gravis: increase muscle strength
Myasthenia gravis- auto-immune mediated neuromuscular disease characterized by fluctuating muscle weakness and fatigue
Alzheimer’s Disease- neurodegenerative disease characterized by cerebral cortex atrophy (amyloid plaques, neuro-fiber tangles, acetylcholine deficiency)
Glaucoma –increased intraocular pressure
Post-op bowel and bladder atony (loss of tone)
Direct-acting agents
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
Eg bethanechol (Urecholine)
Indirect-acting agents
Cause skeletal muscle contractions
Used for diagnosis and treatment of myasthenia gravis
Used to reverse neuromuscular blocking agents
ie. neostigmine
Used to reverse anticholinergic poisoning, pesticide toxicity
ie: physostigmine, pyridostigmine
Physostigmine
Specific antidote for anticholinergic poisoning
It crosses in the CNS and reverses both central and peripheral anticholinergic effects
Special access program
Acetylcholinesterase inhibitor
Used to treat myasthenia gravis
Used for drug overdoses
Reverses non depolarizing NMBAs post op
Symptoms of pesticide toxicity
Indirect-acting agent
Indirect-acting agent
Used in the treatment of mild to moderate Alzheimer’s disease (helps make more Ach available)
Alzheimer’s have a depletion of acetylcholine
Helps to increase or maintain memory and learning capabilities
Not a cure-helps to slow down the progression of Alzheimer’s Disease
ie: donepezil (Aricept), rivastigmine (Exelon), galantamine (Reminyl)
“SLUDGE”
Salivation Lacrimation Urinary incontinence Diarrhea Gastrointestinal cramps Emesis
+Bradycardia
Side Effects
Side effects are due to 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
Drug Effects
Stimulate intestine and bladder
Increased gastric secretions
Increased gastrointestinal motility
Increased urinary frequency
Stimulate pupil
Constriction (miosis)
Reduced intraocular pressure
Increased salivation and diaphoresis
Cardiovascular effects
Decreased heart rate
Vasodilation
Respiratory effects
Bronchial constriction, narrowed airways
Respiratory
Increased bronchial secretions, bronchospasms, bronchorrhea
Other
Lacrimation, sweating, salivation, miosis
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
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
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 a cure
Therapeutic effects of donepezil may not occur for up to 6 weeks
Atropine is the antidote for treatment of cholinergic crisis (dries up secretions)
Atropine 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
