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Pharmacology > CHOLINERGIC DRUGS > Flashcards

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
Q

Physostigmine

A

-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
Q

Echothiophate

A

Organophosphate (AChE inhibitor)

Used for chronic open-angle, subacute it chronic closure-angle glaucoma after iridectomy

27
Q

Malathion and Parathion

A

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
Q

Tabun, sarin, soman

A

Nerve agents
Among the most potent toxic agents known.

AChE inhibitors

29
Q

Alzheimer’s disease

A

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
Q

Pralidoxime

A

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
Q

Atropine

A 
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
Q

Scopolamine

A

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
Q

Ipratropium & Tiotropium

A

Quaternary ammonium muscarinic antagonists

Use: COPD, asthma

“I PRAy I can breathe soon!”

34
Q

Homatropine & Tropicamide

A

Tertiary amine muscarinic antagonists

Produce mydriasis and cycloplegia

35
Q

Benztropine and Trihexyphenidyl

A

Tertiary amine muscarinic antagonists

Uses:

  • Parkinsonism and the extrapyrimidal effects of antipsychotic drugs. “Park my Benz”
  • acute dystonia
36
Q

Glycopyrrolate

A

Anti muscarinic

Uses:

  • inhibit GI motility
  • prevent bradycardia during surgical procedures
  • reduce airway secretions
37
Q

Tolterodine

A

Anti muscarinic

Use: To treat overactive bladder - reduce bladder spasms and urge urinary incontinence

38
Q

Contraindications of Antimuscarinic Agents

A
  • 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
Q

Mecamylamine & hexamethonium

A

Nicotinic receptor antagonists

40
Q

Tubocurarine

A

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
Q

Succinylcholine

A

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
Q

Hemicholinium

A

Inhibitor if ACh synthesis

Blocks transport of choline into presynaptic neuron (CHT1 receptor block)

Only used as a research tool

43
Q

Vesamicol

A

Inhibits ACh - H+ antiporter ised to transport of ACh into vesicles for storage

Only used as a research tool

44
Q

Botulinum Toxin

A

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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