Drugs Affecting the PNS (Part 2)

Question 1

What are the acetylcholine-like effects?

Answer 1

1: Bradycardia
2: Decrease blood pressure
3: Increase GI motility and secretion
4: Smooth muscle contraction in bladder, uterus, bronchioles, and iris
5: Increased secretions
6: Convulsions
7: Stimulation of autonomic ganglia and adrenal medulla
8: Skeletal muscle contraction

Question 2

What is the mechanism of action for bethanechol?

Answer 2

1: Direct acting parasympathomimetic
2: Muscarinic receptor agonist
3: Acts by directly stimulating detrusor muscle contraction of the urinary bladder

Question 3

What form is bethanechol available in?

Answer 3

Oral

Question 4

What are the main clinical indications of bethenechol?

Answer 4

1: Treatment of choice for detrusor muscle atony
2: Part of symptomatic treatment plan for dysautonomia
3: Increases GI motility
4: Stimulates uterine contractions

Question 5

What are the precautions for bethanechol?

Answer 5

SLUDD signs may be seen with high doses

Question 6

What are the contraindications of bethanechol?

Answer 6

1: Contraindicated in urethral obstruction
2: Contraindicated if GI obstruction present

Question 7

What are overdosing worries with bethanechol?

Answer 7

1: Typically will see excessive muscarinic effects
2: In very high doses, more life0threatening cholingeric signs

Question 8

What are the reversible anticholinesterases?

Answer 8

1: Neostigmine
2: Pyridostigmine
3: Edrophonium

Question 9

What is the main mechanism for the parasympathomimetic indirect-acting drugs?

Answer 9

1: Competitive antagonism of acetylcholinesterase
2: Compete with Ach for acetycholinesterase

Question 10

What is the mechanism of action for Neostigmine?

Answer 10

1: Indirect acting parasympathomimetic
2: Acetylcholinesterase antagonist

Question 11

What form is Neostigmine available in?

Answer 11

Oral tablets or injectable solution

Question 12

What is the onset and duration of action for Neostigmine?

Answer 12

Relatively short

Question 13

What are the clinical indications of Neostigmine?

Answer 13

1: reversal agent of choice for reversal of competitive neuromuscular blockers (NMB)
2: Labeled for treatment of rumen atony
3: Stimulates GI motility and increases bladder emptying
4: May aid in the diagnosis and treatment of myasthenia gravis (MG) in dogs

Question 14

What are the precautions for Neostigmine?

Answer 14

SLUDD signs

Question 15

What are the contraindications for Neostigmine?

Answer 15

1: Peritonitis
2: GI obstruction
3: Urinary tract obstruction
4: Late pregnancy —> risk abortion
5: Presence of other cholinesterase inhibitors —> risk of synergism

Question 16

What is the mechanism of action for pyridostimgine?

Answer 16

1: Indirect acting parasympathomimetic
2: Acetylcholinersterase antagonist

Question 17

What form is pyridostimgine available in?

Answer 17

Oral tablet, extended release tablets, oral syrup or as injectable solution

Question 18

What is the onset and duration of action for Pyridostigine?

Answer 18

1: Generally clinical effects seen ~ 1hr after oral dosing
2: Last longer than neostigmine —> clinically up to 8-12hrs.

Question 19

What are the clinical indications for pyridostimgine?

Answer 19

Treatment of choice for myasthenia gravis in dogs —> long-term maintenance therapy

Question 20

What are the precautions and contraindications for pyridostimgine?

Answer 20

1: SLUDD signs, pre-existing high vagal tone
2: Usually dose-related cholingeric effects

Question 21

What is the mechanism of action for edrophonium?

Answer 21

1: Indirect acting parasympathomimetic
2: Acetylcholinesterase antagonist

Question 22

What form is edrophonium available in?

Answer 22

10mg/mL solution for injection

Question 23

What is the onset and duration of action for edrophonium?

Answer 23

1: Very fast acting —> onset within 1 minute
2: Very short duration —> lasts ~ 10 minutes

Question 24

What are the clinical indications for endrophonium?

Answer 24

1: Main use - Tensilon Test for myasthenia gravis
2: Reversal of non-depolarizing NMB’s

Question 25

What are the precautions and contraindications for edrophonium?

Answer 25

Usually mild SLUDD signs

Question 26

What are the atropine-like effects?

Answer 26

1: Tachycardia 2: Mydriasis 3: Dries secretions 4: Reduces salivation 5: Slows gut 6: Bronchodilation 7: Blurred vision 8: Difficulty with urination

Question 27

What is the mechanism of atropine sulfate?

Answer 27

1: Direct-acting parasympatholytic 2: Muscarinic receptor competitive antagonist 3: Tertiary compound ---> can cross the BBB

Question 28

What form is atropine available in?

Answer 28

Injectable solution

Question 29

What are the clinical indications for atropine?

Answer 29

1: Treatment of bradyarrhythmias/bradycardia 2: Cardiac arrest 3: Reduces upper respiratory and GI secretions 4: Treatment of acetylcholinesterase inhibitor toxicity 5: Treatment of cholingergic crisis

Question 30

What are the precautions for atropine?

Answer 30

1: Transient drop in heart rate seen initially after IV injection, then it will increase rapidly 2: May cause tachycardia or exacerbate tachyarrhythmias 3: Rabbits have endogenous atropinases

Question 31

What are the contraindications for atropine?

Answer 31

1: Glaucoma 2: Tachycardia, tachyarrhythmias 3: Hypothermic bradycardia patients 4: Certain Gi diseases, obstructive urinary tract disease, myasthenia gravis

Question 32

What is the mechanism of action for glycopyrrolate?

Answer 32

1: Direct acting parasympatholytic 2: Muscarinic receptor competitive antagonist 3: Quaternary compound ---> Does not cross the BBB

Question 33

What is the onset and duration of action for glycopyrrolate?

Answer 33

Slower onset and action and longer duration of action compared to atropine

Question 34

What are the clinical indications for gylcopyrrolate?

Answer 34

1: Can be used as a pre-medication as part of an anesthesia protocol 2: Reduces upper respiratory and GI secretions 3: Can be used to reduce hypersialism 4: In horses, shown to be superior in reducing cholingeric adverse effects of imidocarb

Question 35

What are the precautions for gylcopyrrolate?

Answer 35

1: Transient drop in heart rate seen initially after IV injection, then it will increase rapidly 2: May cause tachycardia or exacerbate tachyarrhythmias 3: Rabbits have endogenous atropinases 4: Less likely to cause CNS effects 5: Generally less arrhythmogenic than atropine 6: Duration of action is longer

Question 36

What is the mechanism of action for oxybutynin and propantheline?

Answer 36

1: Direct acting parasympatholytic 2: Muscarinic receptor competitive antagonist 3: GI or urinary antispasmodic agents (Relaxation of the detrusor muscle)

Question 37

Does oxybutynin cross the BBB?

Answer 37

Yes

Question 38

Does propantheline cross the BBB?

Answer 38

No

Question 39

What form is oxybutynin and propantheline available in?

Answer 39

1: Oral tablet 2: ER tablet 3: Syrup 4: Topical

Question 40

What form is glycopyrrolate available in?

Answer 40

IV solution

Question 41

What are the clinical indications of oxybutynin and propantheline?

Answer 41

1: Main use for urinary antispasmodic to treat detrusor muscle instability

Question 42

What are the precautions and contraindications for oxybutynin and propantheline?

Answer 42

1: Potential to cause other parasympatholytic signs 2: Avoid in glaucoma, tachycardia and ileus