Cholinergic Agonist and Antagonist

Question 1

Bethanocol

Answer 1

direct acting muscarinic agonist used to treat:

urinary retention

GERD (increases gastric emptying)

Ileus (increases bowel motility)

Post-op abdominal distention (increases bowel motility)

Question 2

Atropine

Answer 2

PSNS antagonist

sources: deadly nightshade, jimsonweed, stinkweed

Blocks PSNS effects on
HR, salivary secretions, bronchi, bladder tone, GI tone + motility, pupils

should be readily available when administering irreversible cholinesterase inhibitors

Question 3

Common clinical uses of Atropine

Answer 3

Bradycardia

Intestinal hypermotility

Muscarinic agonist poisonoing

Asthma (not first choice)

Peptic ulcer disease (refractory symptoms)

Question 4

Potential adverse effects of atropine

Answer 4

Dry mouth (xerostomia)

Blurred vision

Photophobia

Increased intraocular pressure

Urinary retention

Constipation

Tachycardia

Question 5

Oxybutinin

Answer 5

Muscarinic antagonist

Treats overactive bladder

Avoid urinary retention by not giving too much

Question 6

Cholinesterase Inhibitors

Answer 6

prevent breakdown of Ach by acetylcholinesterase = MORE Ach molecules remaining in synapse = greater activation of cholinergic receptors

Question 7

Neostigmine

Answer 7

reversible cholinesterase inhibitor

use for pt w/ myasthenia gravis (provides relief, not curative)

can reverse certain neuromuscular blocking agents (reverse general anesthesia), used in combination with atropine

should not be used if intestinal blockage, urinary blockage, hx of hypersensitivity

Question 8

Myasthenia Gravis

Answer 8

autoimmune disease: antibodies block, alter, or destroy receptors for Ach at NEUROMUSCULAR JUNCTION

weakness and fatigue of muscles

affects all age groups

prevalence = 2-7/10,000

Question 9

Symptoms of Myasthenia Gravis

Answer 9

can affect any muscle that is voluntarily controlled; cranial muscles affected first followed by limbs

symptoms can improve with rest

tend to progress over time

eye muscles –> face and throat muscles –> altered speaking/impaired voice, difficulty swallowing, problems chewing, limited facial expressions –> neck and limps –> fatigue, SOB

Question 10

Pyridostigmine

Answer 10

generally preferred over neostigmine

longer duration of action and lower incidence of adverse muscarinic effects

Question 11

Typical Signs of Muscarine Poisoning

Answer 11

profuse salivation, tearing, visual disturbances, bronchospasm, diarrhea, bradycardia, hypotension, CV collapse

Question 12

Treatment for Muscarine Poisoining

Answer 12

muscarine antagonist and supportive care (oxygen, mechanical ventilator if needed)

Question 13

Myasthenic Crisis

Answer 13

an UNDERDOSE of essential medication

life threatening medical emergency

respiratory muscles may be so weak that ventilation is inadequate

may be triggered by infection, fever, adverse rxn to meds

Med treatment–> respiratory support, ventilator, neostigmine (improves neuromuscular transmission and increases muscular strength)

Question 14

“Irreversible” Cholinesterase Inhibitors

Answer 14

longer acting

clinically: to treat glaucoma

commonly found in insecticides, agents of chemical warfare

Question 15

Glaucoma

Answer 15

common in >50 years

second leading cause of blindness

different forms, open or closed angled depending on cause of IMPAIRED FLUID DRAINAGE

Question 16

Glaucoma and Blindness

Answer 16

Impaired drainage = fluid accumulation = increased intraocular pressure = optic nerve atrophy = eventual vision loss

Primary open angle glaucoma is most common (gradual, painless, no vision changes at first)

Early detection and treatment CAN prevent blindness

Question 17

Echothiophate

Answer 17

Irreversible Cholinesterase inhibitor

treatment for glaucoma (eye drops)

Enhances muscarinic responses (enhances effect of Ach on PSNS innervated structures of eyes)

promotes neuromuscular effects

Question 18

Cholinergic Crisis

Answer 18

OVERDOSE of cholinesterase inhibitor

Life threatening respiratory failure and flaccid paralysis (Ach overstimulation = diaphragm and muscles stop responding)

Treatment:
Respiratory Support (mechanical ventilation until drug metabolized/excreted)
no drug to reverse excessive stimulation of nictotinic M receptors
Atropine

Question 19

How to differentiate between Myasthenic and Cholinergic Crisis?

Answer 19

Edrophonium chloride (short duration, rapid acting cholinesterase inhibitor)

If MC –> pt. gets stronger
If CC–> no effect/worsen; use atropine instead

Question 20

SLUDGE

Answer 20

Salivation
Lacrimation ("lots of tears")
Urination
Diaphoresis/Diarrhea
GI cramps
Emesis

Question 21

Killer B’s

Answer 21

Bronchospasm, Bronchoconstriction, Bronchorrhea (excessive secretions)

Question 22

DUMBBELS

Answer 22

Diarrhea
Urination
Miosis/muscle weakness
Bronchorrhea
Bradycardia
Emesis
Lacrimation
Salivation/sweating

Question 23

Sources of Muscarinic Poisoning

Answer 23

Excess amounts of …
direct acting muscarinic agonists

cholinesterase inhibitors

muscarine containing mushrooms

tiny amount of..
Sarin nerve agent