Cholinergics Flashcards
Hemicholinium receptor/mechnism
Blocks choline transporter CHT1 preventing uptake and synthesis of acetylcholine
Used for research
Vesamicol receptor/mechanism
Blocks the vesicular ACh-H+ antiporter VAChT preventing storage of ACh
Used for research
Botulinum Toxin receptor/mechanism
Prevents synaptic vesicle fusion inhibiting ACh release (synaptobrevin)
Used in local injection; conditions with excess muscle tone (blepharospasm); wrinkles, HA and pain
Neuromuscular blockers drugs
Tubocurarine and Succinylcholine
Tubocurarine receptor/mechanism
Non depolarizing
Binds to Nm->competitive inhibition
Prevents depolarization
Tubocurarine indication/effect
Anesthesia->muscle weakness and flaccid paralysis
Action can be overcome by AChE inhibitors such as neostigmine or edrophonium
Tubocurarine PK
Minimal oral absorption so need to be IV
Poor membrane penetration
Doesn’t cross BBB
Tubocurarine adverse
May cause histamine release
May bind M receptors
Succinylcholine receptor/mechanism
Depolarizing
Activates Nm causing depolarization -> transient disorganized contraction -> desensitization followed by flaccid paralysis
Succinylcholine indication/effect
Useful for ET intubation
Electroconvulsive therapy
Succinylcholine PK
continuous IV infusion
Rapid hydrolysis by plasma cholinesterase
Rapid onset (1m) and brief duration (5-10m)
Not metabolized effectively at the synapse
Succinylcholine adverse
Malignant hyperthermia an autosomal dominant disorder -> excess release of calcium from the SR; usually when combined with a halogenated anesthetic (Tx dantrolene)
Mecamylamine, Trimethaphan, Hexamethonium receptor/mechanism
Antagonize nicotinic receptors in both parasympathetic and sympathetic autonomic ganglia
Mecamylamine, Trimethaphan, Hexamethonium effects
Arterioles and veins are under predominant sympathetic control (adrenergic) -> dilation, hypotension, etc alpha 1
Block parasympathetics at the heart, iris and ciliaris muscle -> tachycardia, mydriasis, and cycloplegia (far vision)
GI, urinary bladder and salivary gland lose parasympathetics -> reduced motility, secretions; urinary retention, xerostomia (dry mouth)
Sweat glands lose sympathetics -> anhydrosis
Mecamylamine, Trimethaphan, Hexamethonium adverse
Vasodilation Venodilation Hypotension Tachycardia Mydriasis Decreased GI/urinary motility Xerostomia Anhydrosis
Mecamylamine, Trimethaphan, Hexamethonium other
Historically used to treat HTN, but have been replaced due to many undesirable effect
Dirty drugs
Pralidoxime effect
Regenerate cholinesterase after organophosphate poisoning (before aging)
Pralidoxime indication
not used for carbamate poisoning which is reversible and short lived
Pralidoxime other
Positively charged; it does not enter the CNS -> not effect on central sx
Tolterodine effect
Tertiary amine
Relaxes smooth muscle
Tolterodine indication
overactive bladder
Muscarinic antagonists
Atropine Scopolamine Ipratropium and Tiotropium Homatropine, Cyclopentolate, Tropicamide Benztropine, Trihexyphenidyl Glycopyrrolate Tolterodine
Glycopyrrolate indication
Oral: inhibition of GI motility
Parenteral: prevent bradycardia during surgery
Benztropine and Trihexyphenidyl Effects
Restore balance of input after loss of dopaminergic neurons in the nigrostriatal pathway
Benztropine and Trihexyphenidyl Indication
Parkinsonism Extrapyramidal effects ( i.e. drug induced movement disorders) of antipsychotic drugs (D2)
Benztropine and Trihexyphenidyl PK
tertiary amines are able to enter the CNS
Homatropine, Cyclopentolate, Tropicamide effects
Mydriasis and cycloplegia - preferred over atropine because of shorter duration of action
Homatropine, Cyclopentolate, Tropicamide PK
tertiary amines are able to enter the CNS
Ipratropium, Tiotropium effects
Bronchodilation (M3)
Ipratropium, Tiotropium indication
Inhalation Tx of *COPD and adjuvant therapy in asthma
Scopolamine effects/indication
DOC for motion sickness
Blocks short term memory (anesthetic procedures)
Scopolamine other
Belladonna Alkaloids-Tertiary amines
Greater and longer duration of action in the CNS than atropine
Atropine effects
Eye: mydriasis, unreactive to light, cycloplegia (paralysis of ciliaris muscle causing loss of accommodation and adaptation)
GI: antispasmodic; decreases motility (HCl production not affected)
Urinary: decreases hypermotility
CVS: low dose -> bradycardia (presynaptic M2)
moderate to high dose-> tachycardia (atrial M2)
Secretions from salivary, sweat and lacrimal glands are blocked (may increase body temperature)
Atropine indication
Antisialagogue prior to surgery decreases respiratory secretions
Increased HR or Decrease AV block due to excessive vagal tone
OD of cholinergic drugs (farmer spraying parathion)
Death cap mushroom poisoning
Alleviate the muscarinic side effects of AChE drugs