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CHOLINERGIC DRUGS Flashcards

1
Q

2 types of cholinergic agonists

A
  1. Direct-acting: some are selective for muscarinic or for the nicotinic receptor or both —> most therapeutically useful drugs preferentially activate MUSCARINIC receptors
    I. Choline esters
    II. Alkaloids
  2. Indirect-acting: Acetylcholinesterase inhibitors
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2
Q

Direct effects of Acetylcholine

A
  • Vasodilation (M3)

- Decrease in cardiac rate, rate of conduction in SA and AV nodes, and in force of contraction (M2)

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3
Q

Cardiovascular affect - Low dose ACh

A

Fall in BP d/t vasodilation (M3), usually accompanied by REFLEX TACHYCARDIA

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4
Q

Cardiovascular effect- High dose ACh

A

Hypotension (M3) and BRADYCARDIA (M2)

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5
Q

ACh effect on VASCULATURE

A

Release of NO and vasodilation = decreased BP

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6
Q

ACh effect on IRIS

A

Miosis

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7
Q

ACh effect on CILIARY MUSCLE

A

Accommodation of lens to near vision

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8
Q

ACh effect on SALIVARY/SWEAT/LACRIMAL GLANDS

A

Inc. secretions

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9
Q

ACh effect on BRONCHI

A

Bronchoconstriction; inc. secretions

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10
Q

ACh effect on HEART

A

Dec HR; dec conduction velocity

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11
Q

ACh effect on GI TRACT

A

Inc. secretions, peristaltic activity, and tone; relaxation of sphincters

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12
Q

ACh effect on URINARY BLADDER

A

Constriction of detrusor muscle; relaxation of sphincter

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13
Q

Acetylcholine

A
  • Choline ester
  • No systemic therapeutic application d/t multiplicity of actions, and rapid hydrolysis by acetylcholinesterase and plasma butyrylcholinesterase

Uses: to obtain rapid myosin after delivery of lens in cataract surgery and other anterior procedures

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14
Q

Bethanechol

A 
MUSCARINIC agonist (no nicotine activity) 
Resistant to AChE

Uses: 
-postoperative and postpartum urinary retention 
Postoperative ileus
Neurogenic ileus 
- atony of urinary bladder

*ileus- lack of movement somewhere in the intestines that leads to possible obstruction

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15
Q

Carbachol

A

Both muscarinic and nicotinic agonist

Uses:

  • Open angle glaucoma: constricts pupil and relieves IOP
  • Dec. IOP after cataract surgery
  • Miosis during surgery
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16
Q

Methacholine

A

Muscarinic agonist

Uses: Challenge test for diagnosis of asthma

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17
Q

Pilocarpine

A
  • Naturally occurring Alkaloid
  • Partial muscarinic agonist
  • tertiary amine
Uses:
-open and closed angle glaucoma 
-Xerostomia (Sjogren syndrome)
-potent stimulator of sweat, tears, and saliva
“You cry, drool and sweat on your PILOw”
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18
Q

Low dose Nicotinic effects

A

CVS: mainly sympathometic effects - inc. HR and BP d/t catecholamine release from adrenal medulla

GI and urinary tracts: largely parasympathomimetic - N/V, diarrhea, and voiding of urine.

Initial stimulation of salivary and bronchial secretions

19
Q

High dose Nicotinic effects

A

Causes ganglionic blockade d/t prolonged depolarization

Neuromuscular blackade

20
Q

Edrophonium

A

Binds reversibly to the active site of acetylcholinesterase

Short lived (2-10 min)

Quaternary ammonium

Uses:

  • Dx of myasthenia gravis
  • Used to reverse the neuromuscular block produced by non-depolarizing muscular blockers
21
Q

Carbamates

A

Form a covalent bond with AChE

Bond spontaneously hydrolyzes w/in 30 minutes - 6 hrs

Physostigmine, neostigmine, pyridostigmine

22
Q

Organophosphates

A

Form a covalent phosphorous-enzyme bond at the active site of AChE.
Extremely stable bond.
The phosphorylated-enzyme complex may undergo a process called ageing which further strengthens the bond.

Cause DUMBBELSS:
Diarrhea
Urination
Miosis
Bronchospasm
Bradycardia
Excitation of skeletal muscle
Lacrimation
Sweating
Salivation

Echothiophate, Thiophosphate insecticides (malathion & parathion), Nerve agents (Tabun, Sarin, Soman)

*organophosphate-insecticide poisoning: to regenerate cholinesterase, administer pralidoxime (able to split phosphorous-enzyme bond if given before ageing process has occurred)

23
Q

Neostigmine

A

Quaternary ammonium

Uses:

  • reversal of effects of non-depolarizing neuromuscular blockers after surgery.
  • treatment of myasthenia gravis (although pyridostigmine is most commonly used).
  • prevention/treatment of postoperative distention and urinary retention.

Adverse effects:
-salivation, flushing, low bp, nausea, abd pain, diarrhea

24
Q

Pyridostigmine

A

Quaternary ammonium

Uses:
-treatment of myasthenia gravis (most commonly used anticholinesterase for this indication)
“Pyridostigmine get rid of myasthenia gravis”

25
Physostigmine
-tertiary amine Uses: -treatment of overdose of anticholinergic drugs “Physostigmine “PHYxes” atropine overdose” Note: should not be given to a pt w/ suspected TCA overdose b/c it can aggravate depression of cardiac conduction. Adverse effects: - effects on CNS may lead to convulsions at high doses - bradycardia - accumulation of ACh at NMJ, causing skeletal muscle paralysis
26
Echothiophate
Organophosphate (AChE inhibitor) Used for chronic open-angle, subacute it chronic closure-angle glaucoma after iridectomy
27
Malathion and Parathion
Thiophosphate insecticides (organophosphates) Activated in body by conversion to oxygen analogs. Malathion is rapidly metabolized in birds and mammals but not insects —> considered safe enough for sale to general public Parathion is not detoxified in vertebrates and this is more dangerous than malathion —> not available for general public use
28
Tabun, sarin, soman
Nerve agents Among the most potent toxic agents known. AChE inhibitors
29
Alzheimer’s disease
Pts have reduced cerebral production of choline acetyl transferase —> dec. ACh synthesis DOC: centrally acting cholinesterase inhibitors to attempt to compensate for the depletion of ACh in the cerebral cortex and hippocampus Donepezil, rivastigmine, galantamine —> all orally taken “Alzheimer’s patients GALlANtly swim DowN the RIVer”
30
Pralidoxime
Can reactivate inhibited AChE * unable to reverse the central effects of organophosphate insecticide poisoning b/c it is unable to enter the CNS d/t it’s + charge
31
Atropine
``` Muscarinic antagonist Blocks DUMBBeLLS ( doesn’t block excitation of skeletal muscle and CNS as those are mediated by nicotinic receptors) ``` Uses: - as an antisialogogue, prior to surgery, when reduction of secretions of the resp. tract are needed - to inc HR or dec AV block - as an antidote for overdose of cholinergic drugs Adverse effects: - inc body temp d/t dec sweating - rapid pulse - dry mouth - dry, flushed skin - cycloplegia - constipation - disorientation -in older pts, use may exacerbate an attack of glaucoma as it induces mydriasis and cycloplegia Tertiary amine
32
Scopolamine
Produces peripheral effects similar to atropine; greater actions on the CNS and longer duration of action Uses: - one of the most effective anti-motion sickness drugs available; administered transdermally via patch Unusual affect: blocks short term memory
33
Ipratropium & Tiotropium
Quaternary ammonium muscarinic antagonists Use: COPD, asthma “I PRAy I can breathe soon!”
34
Homatropine & Tropicamide
Tertiary amine muscarinic antagonists Produce mydriasis and cycloplegia
35
Benztropine and Trihexyphenidyl
Tertiary amine muscarinic antagonists Uses: - Parkinsonism and the extrapyrimidal effects of antipsychotic drugs. “Park my Benz” - acute dystonia
36
Glycopyrrolate
Anti muscarinic Uses: - inhibit GI motility - prevent bradycardia during surgical procedures - reduce airway secretions
37
Tolterodine
Anti muscarinic Use: To treat overactive bladder - reduce bladder spasms and urge urinary incontinence
38
Contraindications of Antimuscarinic Agents
- pts w/ angle-closure glaucoma - pts w/ BPH - elderly (should be used w/ caution) —> are very sensitive to cholinergic blockade d/t central cholinergic hypofxn and dysfxn in ageing and dementia, respectively
39
Mecamylamine & hexamethonium
Nicotinic receptor antagonists
40
Tubocurarine
Prototype drug for ‘non-depolarizing (competitive) blockers’ of NMJ MOA: bind to nicotinic receptor & prevent ACh binding thus preventing depolarization of muscle cell membrane and inhibit muscular contraction. Use: During anasthesia, the IV administration of a nondepolarizing blocker causes skeletal muscles to become totally flaccid and inexcitable to stimulation PK: given IV (oral absorption is minimal w/ poor membrane penetration and don’t cross BBB) Adverse: Autonomic- some are moderate muscarinic receptor blockers. Histamine- tubocurarine may cause histamine release. Action can be overcome by increasing synaptic ACh concentration (ie: w/ neostigmine or edrophonium)
41
Succinylcholine
Depolarizing neuromuscular blocker MOA: bond to nicotinic receptor and act like ACh to cause end-plate depolarization —> spread of depolarization to adjacent membranes = disorganized contraction of muscle motor units —> Succinylcholine not metabolized effectively @ synapse so membrane remains depolarized and unresponsive to additional impulses —> flaccid paralysis PK: given continuous IV. Rapidly hydrolyzed by plasma cholinesterase. Extremely brief duration of action (5-10 min) and rapid onset (1-1.5 min) Uses: useful for rapid endotracheal intubation. Also used during ECT. Adverse: malignant hyperthermia- AD disorder of skeletal muscle —> caused by stimulus elicited excessive Ca2+ release from SR. One of the main causes of death in anesthesia. Treated w/ DANTROLENE, which blocks Ca2+ release from SR = reduced heat production and muscle relaxation
42
Hemicholinium
Inhibitor if ACh synthesis Blocks transport of choline into presynaptic neuron (CHT1 receptor block) Only used as a research tool
43
Vesamicol
Inhibits ACh - H+ antiporter ised to transport of ACh into vesicles for storage Only used as a research tool
44
Botulinum Toxin
Protein produced by anaerobic Clostridium botulinum. Neurotoxin- prevents synaptic vesicle fusion w/ the axon terminal membrane = no ACh release Use: - treatment of several diseases associated with increased tone (such as torticollis, achalasia, strabismus, blepharospasm, etc) - cosmetic use for facial wrinkles - various headache and pain syndromes

Pharmacology (19 decks)

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