ANS 1 (Parasympathetic) Cholinergic Antagonists Flashcards
Drugs Under Muscarinic Blockers
Atropine /hyoscyamine Scopolamine/ hyoscine Hematropine, Cyclopentolate, Tropicamide Ipratropium bromide Pirenzepine Benztropine, Trihexyphenidyl, Oxybutyrin Dicyclomine Propantheline other drugs
prototype anticholinergic
central and peripheral muscarinic (1-5) blocker
Atropine / Hyoscyamine
Dose dependent (atropine) : What is the order of its acions?
1) Decreased salivary and bronchial secretions
2) dec sweating
3) mydriasis, tachycardia
4) inhibition of voiding
5) dec GI motility
6) dec gastric secretions
SE/AE of Atropine
Mydriasis Alice in Wonderland (5) mad as a hatter - hallucinations Blind as a bat - blurring of visions dry as a bone red as a beet - tachycardia, vasodilation hot as a hare - fever / hyperthermia
CI of Atropine
glaucoma, prostatic hypertrophy( inflamed and block the path of urine), heart disease, obstructive bowel disease
M(1-3) blocker
greater action on CNS and longest duration of axn than atropine
more CNS depression at low doses than atropine
more potent at eye and glands than atropine
Less potent at heart, lungs and GI tract than atropine
Scopolamine (hyoscine)
prevents motion sickness (transdermal), nausea and vomiting
blocks short-term memory
causes amnesia and sedation
Scopolamine (hyoscine)
produces twilight sleep (when given with morphine) -insensitivity to pain without loss of cosciuosness and to relieve the pain of childbirth
(morphine=w/o pain)
this drug= w/o memory of the pain
Scopolamine (Hyoscine)
Produces Mydriasis for opthalmoscopic examination
HTC: Homatropine, Tropicamide, Cyclopentolate
M (1-4) blocker
treatment of asthma and COPD
ACh at lungs: bronchodilation, decreased bronchial secretions
Ipratropium bromide
treatment of COPD
Tiotropium
M1 blocker
selective for muscarinic receptor in the stomach
decrease secretion of acid and pepsin
tx of PUD (dec gastric secretion and acidity)
Pirenzepine
M (1-3) blockers
tx of Parkinson’s disease, extrapyramidal disorders
TBO
Trihexyphenidyl, Benztropine , Oxybutnin
M (1-3) blocker
tx of hypermotility of bowel
Dicyclomine
M (1-3) blocker
adjunct for peptic ulcers to dec acid secretions
Propantheline
Other agents that have anticholinergic effects
Antihistamines
Antipsychotics
Tricyclic antidepressants (TCA)
Opioids
MOA of NM Blockers/Skeletal muscle relaxants
block nicotinic receptors causing paralysis
2 divisions of NM Blockers
Competitive Depolarizing
Competitive Non- Depolarizing
Drugs under Competitive Nondepolarizing NM Blockers
Vecuronium Atracurium, Cisatracurium Pancuronium Tubocurarine Mivacurium Rocuronium Pipecuronium, Doxacurium
Drugs (Competitve Depolarizing NM Blockers)
Succinylcholine
NM blockers that compete with ACh at nicotinic receptors, prevents depolarization of the muscle cell membrane and inhibit muscular contraction (noncontraction)
Nondepolarizing NM BLockers
- adjunct to anesthesia: muscle relaxant, eases intubation and ventilation, eases orthopedic manipulation, controls respiration during chest surgery
- has short duration 25-40 min
- very little histamine release
Vecuronium
useful in mechanical ventilation of critically ill patients
ideal for patients with kidney and liver failure
hs short duration of action(25-40 min) for short surgical procedures
AE: moderate histamine release (hypotension, vasodilation)
Atracurium
No histamine release
Cisatracurium
has vagolytic actions
used when elevated heart rate is desired
AE: tachycardia
No histamine release
Pancuronium
Competitive nondepolarizing nm blockers
Prevents fascications associated with succinylcholine administration
Tubocurarine
Competitive nondepolarizing nm blockers
Useful for short surgical procedures, has short duration of action (15-20 min)
Hydrolyzed by plasma AChE
Mivacurium
Conpetitive nondepolarizing nm blocker
Useful for tracheal intubation in patients with gastric contents
Rapid onset: 1-3 min
Duration: 15-60 min
Rocuronium
Competitve nondepolarizing nm blockers adjunct to anesthesia in long surgery cases
Long duration in px with renal dysfunction
AE: prolonged nm blockade
Duration: 40-240 min
Pipecuronium
Doxacurium
prevents the fasciculations associated with succinylcholine (which is a competitive depolarizing) administration
AE: hypotension, bronchospasm
Tubocurarine
useful for short surgical procedures (15-20 mins duration)more rapid recovery from blockade
hydrolyzed by plasma AChE
Mivacurium
useful for tracheal intubation in patients with gastric contents
rapid onset (1-3 min)
duration (15-60 min)
minimal cardiovascular effect
Rocuronium
adjunct to anesthesia in long surgery cases
long duration in px with renal dysfunction
AE: prolonged nm blockade
duration: 20-240 min
Pipecuronium, Doxacurium
NM blockers drug interaction:
overcome the action of nondepolarizing blockers (as antidote?)
NM blockers drug interaction w/ Cholinesterase Inhibtior ( Neostigmine, Edrophonium, Physostigmine)
NM blockers drug interaction:
ehance NM blockade by exerting a stabilizing axn at the NMJ
NM blockers drug interaction w/ halogenated hydrocarbon anesthetics
NM blockers drug interaction:
inhibit ACh release from cholinergic nerves by competing with Ca ions
NM blockers drug interaction w/ aminoglycoside antibiotics
NM blockers drug interaction: may increases nm block of nondepolarizing and depolarizing blockers ; dec muscular contraction
Ca channel blockers
Drug/s for competitve nondepolarizing nm blocker
Succinylcholine
T/F : competitve depolarizing nm blocker effects are reversible by AChE
False
Phase of nondepolarizing nm blocker :
- opening of the Na channel associated with the nicotinic receptors
- fasciculations/contractions
Phase 1
Phase of nondepolarizing nm blocker :
- gradual repolarization as the sodium channel closes or is blocked /relaxation
- resistance to depolarization
- flaccid paralysis
Phase 2
Order of paralysis of Succinylcholine
1) fasciculations in chest and abdomen
2) neck, arms, legs
3) facial, pharynx, larynx
4) respiratory muscles
Useful when rapid endotracheal intubation is required during induction of anesthesia
Onset= 30-60 sec
Duration= 3-5 min
Succinylcholine
Condition wherein there is a muscle rigidity and hyperpyrexia?
Treatment for this condition?
Malignant hyperthermia
Tx: dantrolene ( blocks release of ca from sarcoplasmic reticulum if muscle cells) and rapidly cooling the patient
Given in prereversal stage of reversing nm blockade
- to prevent bradycardia, salivation, other muscarinic effect
Atropine or glycopyrrolate
Low dose of nicotine
Ganglionic stimulation
Depolarization
Inc bp and heart rate
Inc motor activity if bowel
High dose of nicotine
Ganglionic blockade
Dec bp
Ceases Git and bladder activity
Competitive nicotinic ganglionic blocker
Tx of moderately severe to severe htn
Mecamyline
Short acting competitive nicotinic ganglionic blocker
Tx of hypertensive emergencies caused by pulmonary edema or dissecting aortic aneurysm
Trimethaphan
Blockade is by occupying sites in or on the nicotinic ion CHANNEL
First drug effective for htn management
Hexamethonium
