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MTP > Exam 3: Muscarinic Antagonists > Flashcards

Exam 3: Muscarinic Antagonists Flashcards

1
Q

Describe the mechanism of action for muscarinic cholinergic antagonists?

A
  1. Competitive antagonist
  2. Competes with ACh at muscarinic receptors
  3. Blocks ACh in PNS and CNS
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2
Q

What kind of muscarinic receptors are blocked by muscarinic cholinergic antagonist?

A
  1. All parasympathetic postganglionic sites on target tissues
  2. Cholinergic sympathetic postganglionic sites on sweat glands
  3. Muscarinic receptors on neurons and the CNS
  4. Sites with muscarinic receptors lacking cholinergic innervation there no physiological effect
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3
Q

What are the types of antimuscarinic drugs?

A
  1. Tertiary amines and alkaloids
  2. Quaternary amines
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4
Q

What are the properties of tertiary amines and alkaloids antimuscarinic drugs?

A
  1. Lipid soluble
  2. Generally good absorption
  3. Penetrate into brain
  4. High VOD
  5. Highly selective for muscarinic receptor over nicotinic receptors
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5
Q

What are the properties of quaternary amines as antimuscarinic drugs?

A
  1. Permanently charged amines
  2. Generally opposite properties of tertiary amines and alkaloids
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6
Q

Where does atropine derive from?

A
  1. Deadly nightsade
  2. Jimsonweed
  3. Thorn-apple
  4. Stinkweed
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7
Q

How does atropine compare to acetylcholine?

A
  1. Both contain ester and nitrogen
  2. Atropine nitrogen is ionizable
  3. Both contain amine and ester that is important to binding groups
  4. Aromatic ring on atropine is an extra bulky binding group
  5. Atropine bind more strongly to receptor than ACh
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8
Q

What are symptoms of low dose (0.25-0.5mg) atropine exposure?

A
  1. Decreased salivation
  2. Decreased sweating
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9
Q

What are symptoms of low-moderate dose (1-2mg) atropine exposure?

A
  1. Mydriasis
  2. Tachycardia
  3. Decreased gastric acid secretion
  4. Dry mouth and thirst
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10
Q

What are symptoms of moderately high dose (4-8mg) atropine exposure?

A
  1. Difficult urination
  2. Decreased GIT motility
  3. Hot and dry skin (increased temperature)
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11
Q

What are symptoms of high dose (>10mg) atropine exposure?

A
  1. Very high temperature
  2. Rapid pulse
  3. Hallucinations
  4. Death
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12
Q

How can one recognize antimuscarinic overdose?

A
  1. Dry as a bone
  2. Blind as a bat (dilation of pupils, blocks ciliary contractions)
  3. Red as a beet (atropine rash)
  4. Hot as a hare (hyperpyrexia)
  5. Mad as a hatter
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13
Q

What is scopolamine?

A

Henbane that is the highly invasive and noxious weed

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14
Q

How does scopolamine differ from atropine?

A

1.Crosses th BBB more readily
2. Therapeutic use for motion sickness
3. More CNS effect at lower doses than atropine
4. At higher doses, the peripheral toxic effects of scopolamine and atropine are very similar.
5. Both are antimuscarinics

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15
Q

Why is scopolamine preferred prophylactic drug for motion sickness?

A
  1. One dose (4-6hrs)
  2. Multiple routes of administration
  3. Transderm-scop patch protects at least 72hrs
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16
Q

What are the side effects of scopolamine?

A
  1. Dry mouth and drowsiness
  2. Blurred vision and amnesia
  3. Rare psychotic episodes
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17
Q

What is the active ingredient of most OTC motion sickness preparations?

A

Antihistamines

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18
Q

Identify this drug

A

Peirenzepine: M1 selectivity and for peptic ulcer disease

19
Q

Identify this drug

A

Dicyclomine (Bentyl): IBS hypermotility

20
Q

Identify this drug

A

Tropicamide (Mydriacyl, Tropicacyl): Mydriatic cycloplegic refraction

21
Q

Identify this drug

A

Cyclopentolate (Cyclogyl): Mydriatic, cycloplegic refraction

22
Q

What are examples of antimuscarinic drugs?

A
  1. Atropine
  2. Scopolamine
  3. Pirenzepine
  4. Dicyclomine
  5. Tropicamide
  6. Cyclopentolate
23
Q

What is voiding?

A

Coordination of both the ANS and somatic NS controlled by the pontine micturition center in the brainstem

24
Q

What are the parasympathetic receptors associated with micturition?

A

Muscarinic in the pelvic nerve: Bladder causes contraction

25
Q

What are the sympathetic receptors associated with micturition?

A

Adrenergic in hypogastric nerve

26
Q

What are the adrenergic receptors found in the hypogastric nerve?

A
  1. a1 - adrenergic (contracts): Trigone, bladder neck, urethra and Maintains continence by contraction of bladder neck smooth muscles
  2. b2 - adrenergic (relaxes): Bladder neck and body of bladder
    Relaxes bladder neck on void
    Relaxes bladder body for storage (minor)
27
Q

Describe the storage reflex in the bladder?

A
  1. Increased sympathetic tone
  2. Decreased parasympathetic tone
28
Q

Describe the process of micturition in the bladder?

A
  1. Increased parasympathetic tone
  2. Decreased sympathetic tone
29
Q

What are the symptoms of an overactive bladder?

A
  1. Urinating eight or more times per day
  2. Waking up more than twice a night to urinate
  3. An overwhelming and sudden need to urinate
  4. Leakage of urine
30
Q

What are examples of antimuscarinics used to treat overactive bladders (urogenital antispasmodics)?

A
  1. Flavoxate HCl (Urispas)
  2. Oxybutynin HCl (Ditropan XL, Oxytrol, Gelnique)
  3. Tolterodine (Detrol IR & LA)
  4. Darifenacin (Enablex)
  5. Solifenacin (Vesicare, Vesicare LS)
  6. Trospium (Sanctura)
  7. Fesoterodine (Toviaz)
31
Q

What is the function of Urogenital Antispasmodics?

A

Block relaxation of the trigone (signals fulness) and sphincters

32
Q

What is the function of Flavoxate HCl (Urispas)?

A

Oral urinary antispasmodic
Relaxes spasms, increases capacity of bladder

33
Q

What is the function of Oxybutynin HCl (Ditropan XL, Oxytrol, Gelnique)?

A

Decreases hyperreflexively of bladder and urge to void
Available as generic, OTC transdermal patch, and gel

34
Q

What is the function of Oxybutynin HCl Tolterodine (Detrol IR & LA)?

A

Used for urinary incontinence, frequency and
urinary urgency, & bed wetting.
Causes detrusor muscle relaxation

35
Q

What is the binding selectivity of Darifenacin (Enablex)?

A

M3

36
Q

What is the binding selectivity of Solifenacin (Vesicare, Vesicare LS)?

A

M3

37
Q

Describe the structure of Trospium (Sanctura)?

A

Quaternary amine therefore permanent charge

38
Q

How does Fesoterodine (Toviaz) differ from other over-active bladder?

A
  1. Non-selective muscarinic receptor antagonist
  2. Rapidly hydrolyzed by esterases to active metabolites (5-hydroxymethyl tolterodine)
  3. Conversion is rapid and extensive
39
Q

How do we improve urinary retention?

A
  1. Block parasympathetic cholinergic tone with antimuscarinic antagonists
  2. Allows noradrenergic sympathetic tone to dominate causing Detrusor muscle relaxation and Sphincter contraction
40
Q

How effective are Antimuscarinic Therapy for Over Active Bladder?

A
  1. Modestly effective with side effects that can limit usefulness
  2. Patient are encouraged to try lifestyle changes before takinf
  3. Extended release formulations may cause fewer side effects.
    Ditropan XL, Oxytrol (transdermal), Detrol LA, Sanctura, Vesicare, Enablex
41
Q

What are the side effects of using antimuscarinic for over active drug therapy?

A
  1. Dry mouth
  2. Constipation
  3. Blurred vision
  4. Dizziness
42
Q

What is Mirabegron (Myrbetriq)?

A
  1. Selective Beta-3 Adrenergic Receptor Agonists that is used to treat OAB (urinary incontinence, urgency, and frequency)
  2. Increases bladder capacity by relaxing detrusor smooth muscle during storage phase of bladder fill cycle
43
Q

What are the side effects of Mirabegron (Myrbetriq)?

A
  1. Increased BP
  2. Nasopharyngitis
  3. Dry mouth

MTP (15 decks)

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