VII - Cholinergic Pharmacology Flashcards
Primary neurotransmitter in all autonomic ganglia and at the synapses between parasympathetic post-ganglionic neurons and their effector cells
acetylcholine
Primary neurotransmitter at the somatic (voluntary) skeletal muscle neuromuscular junction
acetylcholine
Steps in Cholinergic Stimulation
synthesis, storage, release, termination
Cholinergic Stimulation: Step 1
SYNTHESIS - ACh is synthesized from acetyl CoA and choline by the enzyme choline acyltransferase (ChAT)
Cholinergic Stimulation: choline transport is inhibited by
hemicholinium
Cholinergic Stimulation: Step 2
STORAGE - ACh is actively transported into vesicles for storage by vesicle-associated transporter (VAT)
Cholinergic Stimulation: ACh vesicle storage is inhibited by
vesamicol
Cholinergic Stimulation: Step 3
RELEASE - entry of Ca triggers interaction among SNARE proteins (VAMPs, SNAPs)
Cholinergic Stimulation: alters synaptobrevins to prevent release of ACh
botulinum toxin
Cholinergic Stimulation: Step 4
TERMINATION - degradation of ACh into choline and acetate by acetylcholinesterase
Cholinergic Stimulation: inhibits acetylcholinesterase
Indirect-Acting Cholinomimetics: neostigmine, carbamates, organophosphates
Cholinergic drugs are not very useful for systemic therapy because
their effects are not sufficiently selective
Cholinoreceptors: nerve endings, Gq-coupled, increase IP3, DAG cascade
M1
Cholinoreceptors: heart, some nerve endings, Gi-coupled, decrease cAMP, activates K+ channels
M2
Cholinoreceptors: effector cells of smooth muscles, glands and endothelium, Gq-coupled, increase IP3, DAG cascade
M3
Cholinoreceptors: ANS ganglia, ion channel, depolarizes, action potential
Nn
Cholinoreceptors: neuromuscular end-plate, ion channel, depolarizes, action potential
Nm
Betanechol: Class
cholinomimetic - direct-acting, muscarinic
Betanechol: MOA
activates M3
Betanechol: Uses
bladder and bowel atony (post-op, spinal cord injury)
Betanechol: Side Effects
cyclospasm, diarrhea, urinary urgency, vasodilation, reflex tachycardia, sweating
Pilocarpine: Class
cholinomimetic - direct-acting, muscarinic
Pilocarpine: MOA
activates M3 in ciliary muscle (inc. aqueous humor outflow) and salivary glands (inc. salivation)
Pilocarpine: Uses
glaucoma, Sjorgen syndrome, Sicca syndrome
Pilocarpine: Side Effects
miosis, BOV (cyclospasm)
Nicotine: Similar Drug
Varenicline
Nicotine: Class
cholinomimetic - direct-acting, nicotinic
Nicotine: MOA
activates Nn and Nm
Nicotine: Uses
smoking cessation
Nicotine: Side Effects
generalized ganglionic stimulation: hypertension, tachycardia, nausea, vomiting, diarrhea
Nicotine: Overdose
convulsions, paralysis, coma
CNS stimulation, miosis, spasm of accomodation, bronchocostriction, excessive GIT/GUT smooth muscle activity, increased secretory activity, vasodilation
Muscarinic Toxicity
Muscarine and similar alkaloids are found in these mushrooms
Inocybe, Amanita muscaria
Symptoms of Mushroom Poisoning
nausea, vomiting, diarrhea
ganglionic stimulation, blockade of neuromuscular end-plate depolarization (fasciculations, paralysis), CNS toxicity (convulsions, CNS depression)
Nicotinic Toxicity
Bind to cholinesterase and undergo hydrolysis releasing the alcohol portion
Indirect-Acting Cholinomimetics
The _____ portion of indirect-acting cholinomimetics is retained and slowly released to prevent binding and hydrolysis of endogenous acetylcholine which amplifies ACh effects.
acidic portion
Edrophonium: Class
cholinomimetic - indirect-acting
Edrophonium: MOA
inhibits acetylcholinesterase, amplifies endogenously released ACh
Edrophonium: Uses
diagnosis of Myasthenia Gravis (Tensilon Test), differentiation of cholinergic crisis and myasthenic crisis
Side Effects: miosis, salivation, nausea, vomiting, diarrhea, bradycardia
Edrophonium, Neostigmine, Rivastigmine
Edrophonium: IV
very short-acting
Neostigmine: Similar Drugs
pyridostigmine, physostigmine
Neostigmine: Class
cholinomimetic - indirect-acting
Neostigmine: MOA
inhibits acetylcholinesterase, amplifies endogenously released ACh
Neostigmine: Uses
treatment of Myasthenia Gravis, reversal of non-depolarizing neuromuscular blockade, Ogilvie syndrome, glaucoma (physostigmine)
Side Effects: miosis, salivation, nausea, vomiting, diarrhea, bradycardia
Edrophonium, Neostigmine, Rivastigmine
Neostigmine: muscarinic effects are blocked by
Atropine
Autoimmune destruction of nicotinic ACh receptors, fluctuating muscle, weakness, ocular symptoms, bulbar symptoms, proximal muscle weakness
Myasthenia Gravis
Myasthenia Gravis: acute worsening of symptoms due to infection, stress or undermedication
myasthenic crisis
Myasthenia Gravis: excessive activation of cholinoreceptors, skeletal muscle weakness, parasympathetic signs due to overmedication
cholinergic crisis
Edrophonium _____ muscle strength in myasthenic crisis.
improves
Edrophonium _____ muscle strength in cholinergic crisis.
weakens
Rivastigmine: Similar Drugs
galantamine, donepezil, tacrine
Rivastigmine: Class
cholinomimetic - indirect-acting
Rivastigmine: MOA
inhibits acetylcholinesterase, amplifies endogenously released ACh
Rivastigmine: Uses
Alzheimer’s Disease
Side Effects: miosis, salivation, nausea, vomiting, diarrhea, bradycardia
Edrophonium, Neostigmine, Rivastigmine
Organophosphate Poisoning Symptoms
diarrhea, urination, miosis, bronchospasm, bradycardia, excitation (skeletal muscle, CNS), lacrimation, sweating, salivation
Atropine: Class
cholinergic antagonist - muscarinic
Atropine: MOA
competitively blocks all muscarinic receptors
Atropine: Uses
antidote for organophosphate poisoning (first choice), mydriatic, cycloplegic, bradycardia, hypersalivation
Side Effects: tachycardia, mydriasis, cycloplegia, skin flushing, delirium, hallucinations
Atropine
Atropine: No effect on _____ of organophosphate toxicity
nicotinic signs
Pralidoxime: Class
cholinesterase regenerator, antidote
Pralidoxime: MOA
binds with phosphorus of organophosphate, breaks organophosphate bond with cholinesterase
Pralidoxime: Uses
antidote for organophosphate poisoning and nerve gas poisoning (sarin, tabun)
Pralidoxime: Side Effects
muscle weakness
Pralidoxime: Administration
must be administered before 6-8 hours of organophasphate bond with cholinesterase occurs
Prototype non-selective muscarinic blocker, found in Atropa belladonna, tertiary amine that readily crosses membrane barriers
Atropine
Atropine: Similar Drugs
homatropine, cyclopentolate, tropicamide
Benztropine: Similar Drugs
biperiden, trihexyphenidyl
Benztropine: Class
cholinergic antagonist - muscarinic
Benztropine: MOA
competitively blocks all muscarinic receptors, restores neurotransmitter balance in the basal ganglia
Benztropine: Uses
Parkinson’s Disease
Benztropine: Side Effects
BOV, dry eyes, constipation, dry mouth, urinary retention
Benztropine: Reduces _____ more than bradykinesis or rigidity
tremors
Muscarinic Antagonists for Parkinsonism
trihexyphenidyl, benztropine, biperiden
Ipratropium: Similar Drugs
tiotropium
Ipratropium: Class
cholinergic antagonist - muscarinic
Ipratropium: MOA
blocks muscarinic receptors in bronchial smooth muscle, prevents vagal-stimulated bronchoconstriction
Ipratropium: Uses
asthma, COPD
Ipratropium: Side Effects
dry mouth, cough, nasal dryness
Ipratropium: More effective and less toxic than _____ in patients with COPD and heart disease
beta-agonists
Preferred bronchodilator in patients with COPD and heart disease, less likely to cause tachycardia and cardiac arrythmias
Ipratropium
Scopolamine: Class
cholinergic antagonist - muscarinic
Scopolamine: MOA
competitively blocks all muscarinic receptors, antagonizes histamine and serotonin
Scopolamine: Uses
motion sickness
Scopolamine: Side Effects
drowsiness, BOV, dry eyes, constipation, dry mouth, urinary retention
Scopolamine: Application
transdermal patch
Hyperthermia, cutaneous vasodilation, decreased secretions, tachycardia, intraventricular conduction block, constipation, BOV, CNS toxicity
Atropine Toxicity - HOT as a hare, DRY as a bone, RED as a beet, BLIND as a bat, MAD as a hatter
Contraindications for Muscarine Blockers
infants, hyperthermia (decreased sweating), acute angle closure glaucoma, benign prostatic hyperplasia
Competitive pharmacologic antagonists at nicotinic ACh receptors, first successful agents for HPN, adverse blockade
Ganglion Blockers
Hexamethonium: Similar Drugs
trimethaphan
Hexamethonium: Class
cholinergic antagonist - nicotinic
Hexamethonium: MOA
competitively blocks Nn nicotinic ACh receptors
Hexamethonium: Uses
hypertension (obsolete), hypertensive emergencies
Hexamethonium: Side Effects
postural hypotension, dry mouth, BOV, constipation, sexual dysfunction
Important for producing complete skeletal muscle relaxation in surgery
Neuromuscular Blockers
Neuromuscular Blockers: Non-Depolarizing
tubocurarine, pancuronium, atracurium, vecuronium
Neuromuscular Blockers: Depolarizing
succinylcholine