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GI > Decontamination agents and Antiemetics > Flashcards

Decontamination agents and Antiemetics Flashcards

1
Q

Sensory receptor zone

A

–Especially in the stomach and small intestine, the pharynx, and the inner ear; visual, olfactory, and painful stimuli that can also elicit vomiting

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2
Q

Chemoreceptive trigger zone (CTZ)

A
  • -Located in area postrema, on floor of 4th ventricle.
  • -OUTSIDE THE BBB.
  • -Primary region for detection of blood-borne emetics
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3
Q

Vomiting center

A
  • -Connected to chemoreceptive trigger zone
  • -Located in medulla
  • -Responsible for initiation and coordination of complex motor patterns needed for vomiting.
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4
Q

“Higher centers”

A

Responsible for memory, fear, dread, and anticipation

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5
Q

3 major stimuli that activate the vomiting center

A
  • -Mechanical and/or painful stimuli (esp. in inner ear, local GI irritation, pharynx)
  • -Blood borne emetics
  • -Higher centers
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6
Q

How does local GI irritation trigger the vomiting center

A

Irritation–> vagal and sympathetic afferents from the stomach and small intestine that can be modulated by actin of 5HT3 receptors–> solitary tract nucleus and chemoreceptive trigger zone–> vomiting center

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7
Q

How does the gag reflex trigger the vomiting center?

A

Glossopharyngeal and trigeminal afferents–> solitary tract nucleus–> vomiting center

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8
Q

What are the chemoreceptive trigger zone receptors?

A
  • -Serotonin
  • -Histmine
  • -Muscarinics
  • -Opioids
  • -Dopamine
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9
Q

Serotonin receptor locations

A
  • -GI tract* (primary)
  • -Chemoreceptive trigger zone
  • -Inside BBB
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10
Q

Dopamine receptor locations

A
  • -GI tract
  • -CTZ*
  • -BBB
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11
Q

Muscarinic receptor locations

A
  • -GI tract
  • -CTZ
  • -BBB*
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12
Q

Histamine receptor locations

A

Inside BBB

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13
Q

NK1 receptor locations

A

Inside BBB

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14
Q

Cannabinoid receptor location

A

Inside BBB

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15
Q

Opioid receptor locations

A
  • -GI tract
  • -CTX*
  • -BBB
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16
Q

Activated charcoal

A
  • -Absorbs many drugs and poisons because of large SA
  • -Must be given 10:1 by weight
  • -Doesn’t bind Iron, lithium, potassium
  • -Binds EtOH and cyanide poorly
  • -Not useful in cases of corrosive mineral acids or alkalis
  • -Upper GI
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17
Q

Polyethylene glycol-electrolyte solution

A
  • -May help hasten removal of toxins and reduce absorption
  • -Whole bowel irrigation can enhance decontamination after ingesting iron, enteric coated medicines, illicit drugs, foreign bodies
  • -Used for endoscopic procedures
  • -Cathartics
  • -Lower GI
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18
Q

IPECAC

A
  • -Emetic agent
  • -Induces vomiting
  • -Controversial use
  • -Don’t use for poison remedy OTC
  • -Local irritant effect
  • -Acts on CTZ
  • -Emesis may not occur if stomach emptied
  • -15-30 min to effect
19
Q

Antiemetics

A
  • -Gen. more effective at preventing vomiting than stopping emesis once it has started
  • -Often used in combo because they act synergistically
20
Q

Serotonin (5HT3) Anagonists

A
  • -Dolasetron
  • -Granisetron
  • -Ondansetron
  • -Palonosetron
21
Q

Serotonin (5HT3) antagonist MOA

A
  • -Blockade peripheral 5HT3 receptors on primary afferents

- -Also in CTZ and vomiting center

22
Q

Therapeutic uses for serotonin antagonists

A
  • -Drug of choice for chemotherapy induced nausea and vomiting
  • -More effective preventing acute phase (24 hrs after start) if given 30 min before antineoplastic
  • -Not as good for delayed phase
  • -Post-op and post-radiation nausea and vomiting
23
Q

Are serotonin antagonists effective for motion sickness?

A

No

24
Q

Side effects of serotonin antagonists

A
  • -Well tolerated with good safety profiles
  • -Most side effects transient
  • -Constipation, dizziness, mild headache
  • -Small QT elongation, but not clinically relevant
25
Q

What is the most effective drug for most effective agent for motion sickness treatment

A

Scopolamine when given as a transdermal patch

26
Q

Anticholinergic name

A

Scopolamine

27
Q

What are the only truly effective agents for the prevention of cancer chemotherapy induced emesis?

A

Serotonin (5HT3 antagonists)

28
Q

MOA of scopolamine

A
  • -Muscarinic and dopaminergic receptor antagonist in cerebellum –> widely distributed in CNS
  • -Transdermal patch–> decreases side effects compared to oral or parenteral admin
29
Q

Neurokinin receptor 1 (NK1) Antagonist

A

Aprepitant (oral)/ Fosaprepitant (IV)

30
Q

Aprepitant/ fosaprepitant MOA

A

Substance P receptor antagonists. Central “higher order center” NK receptors

31
Q

Therapeutic uses for aprepitant/fosaprepitant?

A

Chemo induced N and V in combo with 5HT3 antagonist and dexamethasone

32
Q

Side effects for aprepitant/fosaprepitant?

A
  • -Generally well tolerated
  • -Fatigue, dizziness, diarrhea
  • -Metabolized by CYP3A4 (esp. some chemo agents! Can make other side effects worse, need to pay attention to bone marrow suppression)
33
Q

Antihistamine drug names

A
  • -Dimenhydrinate
  • -Diphenhydramine
  • -Meclizine
34
Q

Antihistamine (H1) MOA

A
  • -Sedation

- -H1 may not be primary mechanism, may be anti-muscarinic

35
Q

Antihistamine side effects

A
  • -Anticholinergic (confusion, dry mouth etc,)
  • -Drug interactions w/ some antibiotics
  • -Don’t use during pregnancy
36
Q

Dopamine receptor antagonist names

A
  • -Droperidol
  • -Metoclopramide
  • -Prochlorperazine
  • -Promethazine
  • -Thiethylperazine
37
Q

Dopamine receptor antagonists

A
  • -Receptors in CTZ zone
  • -May have muscarinic antagonism?
  • -“Reseting” GI motility
  • -Sedation
38
Q

Cannabinoid names

A

Dronabinol

Nabilone

39
Q

Side effects of cannabinoids

A
  • -Euphoria
  • -Sedation
  • -Hallucinations
  • -Dry mouth
  • -Increased appetite (good for cancer patients)
40
Q

What are cannabinoids often given with?

A

Phenothiazines

41
Q

Corticosteroid MOA in vomiting

A

Unknown

42
Q

Corticosteroids

A

Dexamethasone, methylprednisolone

43
Q

What are corticosteroids used with?

A

5HT3 antagonists and aprepitants

GI (12 decks)

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