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PHARMACOLOGY > Pharm PNS II > Flashcards

Pharm PNS II Flashcards

1
Q

What drugs are DIRECT ACTING ParaysympathoMIMETICS? (choline esters)

A

Bethanechol

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2
Q

What drugs are INDIRECT ACTING ParasympathoMIMETICS?

A
  • Neostigmine
  • Edrophonium
  • Pyridostigmine
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3
Q

What drugs are DIRECT ACTING ParasympathoLYTICS?

A
  • Atropine
  • Glycopyrrolate
  • Oxybutynin
  • Propantheline
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4
Q

If a drug has Acetylcholine-like effects what changes will you see in the body?

A
  • bradycardia (negative chronotropy)
  • decreased blood pressure (negative inotropy + vasodilation)
  • increase GI motility and secretion
  • smooth muscle contraction in:
    • bladder (micturition in contraction of detrusor muscle)
    • uterus
    • bronchioles (bronchoconstriction)
    • iris (mitosis)
  • increased secretions (salivation and lacrimal)
  • convulsions (CNS)
  • stimulation of autonomic ganglia and adrenal medulla
  • skeletal muscle contraction
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5
Q

What is the mechanism of action for drugs that are parasympathomimetics and reversible anticholinesterases?

A
  • competitive antagonism of acetylcholinesterase

- will compete with Acetylcholine (endogenous substance) for acetylcholinesterase which usually breaks it down

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6
Q

What does parasympathoLYTICS do?

A

they lyse the effect of acetylcholine and are also called anticholinergics. They are muscarinic antagonists.

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7
Q

What does parasympathoMIMETICS do?

A

They mimic the effect of acetylcholine and are muscarinic agonists.

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8
Q

What are atropine-like effects?

A
  • tachycardia
  • mydriasis (dilates pupil)
  • dries secretions
  • reduces salivation
  • slows gut
  • bronchodilator
  • blurred vision (cycloplegia)
  • difficulty with urination
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9
Q

If you have a dog under anesthesia and see you have sinus bradycardia. What main drug would you correct with?

A

Atropine

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10
Q

Which of the following is the treatment of choice for Myasthenia Gravis?

A. Pyridostigmine
B. Neostigmine
C. Edrophonium
D. Bethanechol

A

A. Pyridostigmine

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11
Q

Which of the following is used in the testing for Myasthenia Gravis?

A. Glycopyrrolate
B. Neostigmine
C. Edrophonium
D. Bethanechol

A

C. Edrophonium

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12
Q

Which of the following is a contraindications for the use of atropine?

A. Sinus bradycardia
B. 2nd degree AV block
C. Closed-angle glaucoma
D. Nausea

A

C. Closed-angle glaucoma

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13
Q

Compared with atropine, which of the following is true about glycopyrrolate?

A. Lasts longer than atropine
B. Crosses BBB
C. Antagonizes primarily nicotinic receptors
D. Does not treat bradycardia

A

A. Lasts longer than atropine

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14
Q

What are the mechanisms of action of Bethanechol?

A
  • direct acting parasympathomimetic
  • agonist of Acetylcholine

-
Directly stimulates contraction of the urinary bladder via the DETRUSOR MUSCLE

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15
Q

What are the clinical indications of Bethanechol?

A
  • treatment of choice for detrusor muscle atony —> increases detrusor m. Contractility
  • symptomatic tx plan for dysautonomia (degenerative disorder resulting in polyneuropathy)
  • increases GI motility and can aid in tax of equine gastric ulcer syndrome (EGUS)
  • reproduction —> stimulates uterine contraction (less common use)
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16
Q

What are the precautions with Bethanechol?

A
  • SLUDD signs may be seen in higher doses

- can see life threatening cholinergic crisis is in the event of overdose/toxicity (severe bradycardia, bronchospasm)

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17
Q

What are the contraindications of Bethanechol?

A
  • Problematic if patient has urethra obstruction or GI obstruction
  • patient must have patent urethra and intact bladder wall
  • caution with increased GI motility
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18
Q

What is seen in overdose with Bethanechol?

A
  • excessive muscarinic effects like salivation, urination, defication
  • in very high doses will see more life-threatening cholinergic signs (bradycardia, bronchospasm, etc)
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19
Q

What is the mechanism of action for Neostigmine?

A
  • indirect acting parasympathoMIMETIC
  • acetylcholinesterase antagonist
  • relatively short onset (10-30 minutes)
  • duration lasts about 4 hours
20
Q

What are the clinical indications of Neostigmine?

A
  • reversal agent of choice for reversal of competitive neuromuscular blockers (NMB)
  • tx for rumen atony (initiate peristalsis)
  • stimulate GI motility and increase bladder emptying
  • may aid in the diagnosis and treatment of myasthenia gravis in dogs
21
Q

What are the precaution for Neostigmine?

A
  • SLUDD signs which may be more dramatic in patients with pre-existing high vagal tone
  • watch in brachycephalic breeds, GI disease, concurrent medications, etc.
22
Q

What is the mechanism of action of Neostigmine?

A

It is a competitive (reversible) antagonist of acetylcholinesterase

23
Q

What is the onset and duration of Neostigmine?

A

It kicks in about 10-30 minutes and can last 4 hours

24
Q

What are the clinical indications of Neostigmine?

A
  • Reversal agent of choice for reversal of competitive neuromuscular blocks (NMB)
  • tx for rumen atony by initiating peristalsis
  • stimulate GI motility and increase bladder emptying
  • aid in dx and tx of myasthenia gravis
25
Q

What are some precautions for Neostigmine?

A
  • SLUDD signs may be more dramatic with pre-existing vagal tone
  • watch out for brachycephalic breeds, GI disease, concurrent medications
26
Q

What are some contraindications with Neostigmine?

A
  • peritonitis
  • GI obstruction
  • urinary tract obstruction
  • in late pregnancy you risk abortion due to uterine contractions
  • if you have the presence of other cholinesterase inhibitors then you risk SYNERGISM
27
Q

What is the mechanism of action for Pyridostigmine?

A

It is a competitive (reversible) antagonist of acetylcholinesterase

28
Q

What is the onset and duration of Pyridostigmine?

A
  • onset –> 1 hour after oral dose (but faster if given IV)

- duration –> up to 8-12 hours (longer than Neostigmine)

29
Q

What are the clinical indications of Pyridostigmine?

A

It is the treatment of choice for myasthenia gravis in dogs for long term maintenance therapy

30
Q

What are some precautions and contraindications of Pyridostigmine?

A
  • SLUDD signs seen with pre-existing high vagal tone
  • dose-related cholinergic effects
    - GI: nausea, vomiting, diarrhea, hyper salivation
    - increase respiratory secretion, bronchospasm,
    pulmonary edema
    - bradycardia, tachycardia, cardiac arrest
    - muscle cramps and weakness
31
Q

What are the mechanisms of action for Edrophonium?

A

It is a competitive (reversible) acetylcholinesterase antagonist. IV injection is at 10 mg/mL.

32
Q

What is the onset and duration of Edrophonium?

A
  • onset –> very fast acting (within 1 minute)

- duration –> very short (lasts about 10 minutes)

33
Q

What are the clinical indications of Edrophonium?

A

It is used for the Tension test which is used for myasthenia gravis. It is a reversal of non-depolarizing neuromuscular blocks (NMB) but not as commonly used as Neostigmine.

34
Q

What are some precautions and contraindications of Edrophonium?

A
  • SLUDD signs are usually mild

- less commonly but more severe cholinergic crisis (this is dose dependent)

35
Q

Who has the longest duration of action?

A. Neostigmine
B. Pyridostigmine
C. Edrophonium

A

B. Pyridostigmine

36
Q

Who has the shortest duration of action?

A. Neostigmine
B. Pyridostigmine
C. Edrophonium

A

C. Edrophonium

37
Q

What are the mechanisms of action for Atropine sulfate?

A
  • it is a competitive (reversible) antagonist of acetylcholine
  • it is a tertiary compound that can cross the blood brain barrier (poorly @ therapeutic dose)
  • injectable solution is more common and it will ionize in the GI tract
38
Q

What are some clinical indications for Atropine sulfate?

A
  • treatment of bradycardia/bradyarrythmias especially during anesthesia
  • cardiac arrest (not in all CPR cases)
  • reduces respiratory and GI secretions –> Xerostomia (dry mouth)
  • treatment of acetylcholinesterase inhibitor toxicity (organophosphates and carbamates)
  • treatment of cholinergic chrisis (due to anti cholinesterase overdose)
39
Q

What are some precautions with Atropine sulfate?

A
  • drops in heart rate seen initially after IV injection and then will see an increase rapidly
  • may cause tachycardia or exacerbate tachyarrhythmias
  • rabbits have endogenous atropinases (break down atropine) so it is not as effective and should use glycopyrrolate
40
Q

What are some contraindications with Atropine sulfate?

A
  • glaucoma with systemic and ophthalmic use
  • tachycardia/tachyarrhythmias
  • hypothermic bradycardia patients
  • certain GI diseases, obstructive urinary tract, myasthenia gravis
41
Q

What are the mechanisms of action of Glycopyrrolate?

A

It is a competitive (reversible) antagonist of acetylcholine. It is a quaternary compound that DOES NOT cross the blood brain barrier.

42
Q

What is the onset and duration of action with Glycopyrrolate?

A
  • onset –> slower( but IV is fast @ about 1 minute)

- duration –> longer than compared to atropine (most vagolytic effects last about 2-3 hours)

43
Q

What are the clinical indications of Glycopyrrolate?

A
  • same as atropine but slower kinetics may be more favorable depending on the situation
  • can be used as a pre-med for anesthesia
  • reduces respiratory and GI secretions
  • can be used to reduced hypersialism (excessive salivation) which leads to sialocele (accumulation of saliva in surrounding tissue or glands)
  • horses –> great reduction of cholinergic adverse effects of imidocarb
44
Q

What are some precautions with Glycopyrrolate?

A
  • same as for atropine
  • less likely to cause CNS effects because it does not cross the blood brain barrier
  • less arrythmogenic than atropine
  • since duration of action is longer it may interfere with the ability to assess patient heart rate post-op
45
Q

What are the mechanisms of action for Oxybutynin and Propantheline?

A
  • competitive (reversible) antagonist of acetylcholine
  • GI or urinary antispasmodic agents
  • causes the relaxation of the detrusor muscle and allows the bladder to empty more easily
  • Oxybutynin –> widely distributed and CAN cross the blood brain barrier
  • Propantheline –> does NOT cross the blood brain barrier
46
Q

What are the clinical indications of Oxybutynin and propantheline?

A
  • MAIN USE –> treat detrusor muscle instability (hyperactive bladder) and urinary antispasmodic
  • Propantheline can also be used to treat certain bradyarrythmias
47
Q

What are some precautions and contraindications of propantheline and oxybutynin?

A
  • potential to cause other parasympathetic signs (propantheline can stimulate HR)
  • at normal therapeutic dose bladder and GI seem to be only organs affected
  • avoid in glaucoma, tachycardia and ileus

PHARMACOLOGY (6 decks)

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