Drugs Affecting the PNS (Part 2) Flashcards
What are the acetylcholine-like effects?
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
What is the mechanism of action for bethanechol?
1: Direct acting parasympathomimetic
2: Muscarinic receptor agonist
3: Acts by directly stimulating detrusor muscle contraction of the urinary bladder
What form is bethanechol available in?
Oral
What are the main clinical indications of bethenechol?
1: Treatment of choice for detrusor muscle atony
2: Part of symptomatic treatment plan for dysautonomia
3: Increases GI motility
4: Stimulates uterine contractions
What are the precautions for bethanechol?
SLUDD signs may be seen with high doses
What are the contraindications of bethanechol?
1: Contraindicated in urethral obstruction
2: Contraindicated if GI obstruction present
What are overdosing worries with bethanechol?
1: Typically will see excessive muscarinic effects
2: In very high doses, more life0threatening cholingeric signs
What are the reversible anticholinesterases?
1: Neostigmine
2: Pyridostigmine
3: Edrophonium
What is the main mechanism for the parasympathomimetic indirect-acting drugs?
1: Competitive antagonism of acetylcholinesterase
2: Compete with Ach for acetycholinesterase
What is the mechanism of action for Neostigmine?
1: Indirect acting parasympathomimetic
2: Acetylcholinesterase antagonist
What form is Neostigmine available in?
Oral tablets or injectable solution
What is the onset and duration of action for Neostigmine?
Relatively short
What are the clinical indications of Neostigmine?
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
What are the precautions for Neostigmine?
SLUDD signs
What are the contraindications for Neostigmine?
1: Peritonitis
2: GI obstruction
3: Urinary tract obstruction
4: Late pregnancy —> risk abortion
5: Presence of other cholinesterase inhibitors —> risk of synergism
What is the mechanism of action for pyridostimgine?
1: Indirect acting parasympathomimetic
2: Acetylcholinersterase antagonist
What form is pyridostimgine available in?
Oral tablet, extended release tablets, oral syrup or as injectable solution
What is the onset and duration of action for Pyridostigine?
1: Generally clinical effects seen ~ 1hr after oral dosing
2: Last longer than neostigmine —> clinically up to 8-12hrs.
What are the clinical indications for pyridostimgine?
Treatment of choice for myasthenia gravis in dogs —> long-term maintenance therapy
What are the precautions and contraindications for pyridostimgine?
1: SLUDD signs, pre-existing high vagal tone
2: Usually dose-related cholingeric effects
What is the mechanism of action for edrophonium?
1: Indirect acting parasympathomimetic
2: Acetylcholinesterase antagonist
What form is edrophonium available in?
10mg/mL solution for injection
What is the onset and duration of action for edrophonium?
1: Very fast acting —> onset within 1 minute
2: Very short duration —> lasts ~ 10 minutes
What are the clinical indications for endrophonium?
1: Main use - Tensilon Test for myasthenia gravis
2: Reversal of non-depolarizing NMB’s
What are the precautions and contraindications for edrophonium?
Usually mild SLUDD signs
What are the atropine-like effects?
1: Tachycardia
2: Mydriasis
3: Dries secretions
4: Reduces salivation
5: Slows gut
6: Bronchodilation
7: Blurred vision
8: Difficulty with urination
What is the mechanism of atropine sulfate?
1: Direct-acting parasympatholytic
2: Muscarinic receptor competitive antagonist
3: Tertiary compound —> can cross the BBB
What form is atropine available in?
Injectable solution
What are the clinical indications for atropine?
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
What are the precautions for atropine?
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
What are the contraindications for atropine?
1: Glaucoma
2: Tachycardia, tachyarrhythmias
3: Hypothermic bradycardia patients
4: Certain Gi diseases, obstructive urinary tract disease, myasthenia gravis
What is the mechanism of action for glycopyrrolate?
1: Direct acting parasympatholytic
2: Muscarinic receptor competitive antagonist
3: Quaternary compound —> Does not cross the BBB
What is the onset and duration of action for glycopyrrolate?
Slower onset and action and longer duration of action compared to atropine
What are the clinical indications for gylcopyrrolate?
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
What are the precautions for gylcopyrrolate?
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
What is the mechanism of action for oxybutynin and propantheline?
1: Direct acting parasympatholytic
2: Muscarinic receptor competitive antagonist
3: GI or urinary antispasmodic agents (Relaxation of the detrusor muscle)
Does oxybutynin cross the BBB?
Yes
Does propantheline cross the BBB?
No
What form is oxybutynin and propantheline available in?
1: Oral tablet
2: ER tablet
3: Syrup
4: Topical
What form is glycopyrrolate available in?
IV solution
What are the clinical indications of oxybutynin and propantheline?
1: Main use for urinary antispasmodic to treat detrusor muscle instability
What are the precautions and contraindications for oxybutynin and propantheline?
1: Potential to cause other parasympatholytic signs
2: Avoid in glaucoma, tachycardia and ileus
