Cholinergic Antagonist Flashcards
Exam 4
Nicotinic receptor antagonist
- ganglionic blocking agents
- neuromuscular blocking agents
Muscarinic receptor antagonist
- block muscarinic receptor of PSN
- blocking PSN allows SNS to go unopposed
- used to relax smooth muscle, decrease gland secretions, and stimulate heart
Ganglionic blocking agents
- mecamylamine
- prevents stimulation of postsynaptic receptors by ACh released from presynaptic nerve endings
Neuromuscular blocking agents
- bind to nicotinic receptor on skeletal muscle inhibiting neurotransmission leading to muscle weakness and paralysis
- nondepolarizing neuromuscular blocking agents
- depolarizing neuromuscular blocking agents
Nondepolarizing neuromuscular blocking agents
- competitive antagonists of ACh at nicotinic receptors
- Atracurium, cistracurium, pancuronium, rocuronium, vecuronium
Depoarlizing neuromuscular blocking agents
- binds to and continually stimulates nicotinic receptors, inhibiting neuron from further depolarization, preventing neuronal impuses
- Succinylcholine
Eye muscarinic receptor antagonist
- Atropine (mydriasis & bradycardia)
- Homatropine
- Tropicamide
CNS muscarinic receptor antagonist
- Bentropine
- Trihexyphenidyl
- Scopolamine
GI & respiratory muscarinic receptor antagonist
-Glycopyrrolate (decrease mucus production)
GI muscarinic receptor antagonist
- Hyoscyamine
- Dicyclomine
Respiratory muscarinic receptor antagonist
- Ipratopium (asthma and COPD)
- Tiotropium
GU muscarinic receptor antagonist
- Oxybutyinin
- Darifenacin
- Solifenacin
- Tolterodine
MOA of muscarinic antagonist
- compete with ACh for muscarinic receptors at parasympathetic junctions and inhibit nerve stimulation
- reversible antagonist which block M1, M2, or M3 receptors depending on selectivity of the agent
- because they are reversible blockers their effects can overcome by giving larger doses of agonist = more ACh
Anticholinergic effects on eye
- block M3 receptors
- pupillary constrictor muscles are inhibited (relax)
- mydriasis & cycloplegia: paralysis of the accommodation muscle for near vision causing blurred vision
- dry eyes (from decreased tearing)
- clinical use: eye exams to dilate pupils & paralyze lens
Anticholinergic effects on CNS
- agents block several muscarinic receptor subtypes
- sedation
- anti motion sickness action
- anti parkinson action
- amnesia
- delirium
Anticholinergic effects of CVS
- Tachycardia: blockage of M2 receptor in SA node
- Clinical use: Atropine is part of the ACLS for significant bradycardias
Anticholingeric effects on GI tract
- decreased secretions and motility of the GI tract (increase gastric emptying time and intestinal transit time = constipation)
- clinical use: treat symptoms of diarrhea, intestinal spasms - dicylcomine (Bentyl)
Anticholinergic effects on respiratory
- bronchodilation & decrease secretions (block M3 receptor)
- effects is more in airway or lung that is diseased than it is in the healthy lung
- clinical use: COPD and asthma
- Tiotropium (Spiriva)
- Ipratropium (Atrovent)
Anticholinergic effects on GU tract
- relaxes smooth muscle of the bladder wall and slows voiding. Don’t tend to urinate as much
- clinical use: relieve bladder spasm and help those urinating frequently due to bladder spasm (overactive bladder)
- oxybutynin (Detrol)
Anticholinergic effects sweat glands
- antimuscarinic drugs work by blocking receptors causing decreased sweat, increased temp
- clinical use: none, but a major source of morbidity & mortality.
- when anticholinergic drug causes death most often does so by hyperthermia
Cholinergic poisoning
- anticholnergic is cholinerimetic poisoning, such as organophosphates, insecticides, or nerve gas
- symptoms of cholinesterase inhibitor poisoning (DUMBBELSS)
- Diarrhea
- Urination
- Miosis
- Bronchospasm
- Bradycardia
- Excitation of skeletal muscle and CNS
- Lacrimation
- Sweating
- Salivation
- may lead to respiratory failure if untreated
- Atropine blocks DUMBBELSS
Anticholinergic toxicity
- problem for children and elderly
- increased body temp
- dry skin
- flushed skin
- cycloplegia
- disorientation
- urinary retention
- cause acute angle closure glaucoma in elderly
- urinary retention in men with BPH
- hyperthermia in infants
Tx of anticholinergic toxicity
- tx the symptoms
- if fever use a cooling blankets and drugs that lower temp like acetaminophen
- if tachycardic use drugs to slow heart
- Physostigmine can be given in increase ACh (inhibits enzyme that breaks down ACh) when necessary (cholinergic agent)
