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?

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
What is the most effective drug for most effective agent for motion sickness treatment
Scopolamine when given as a transdermal patch
26
Anticholinergic name
Scopolamine
27
What are the only truly effective agents for the prevention of cancer chemotherapy induced emesis?
Serotonin (5HT3 antagonists)
28
MOA of scopolamine
- -Muscarinic and dopaminergic receptor antagonist in cerebellum --> widely distributed in CNS - -Transdermal patch--> decreases side effects compared to oral or parenteral admin
29
Neurokinin receptor 1 (NK1) Antagonist
Aprepitant (oral)/ Fosaprepitant (IV)
30
Aprepitant/ fosaprepitant MOA
Substance P receptor antagonists. Central "higher order center" NK receptors
31
Therapeutic uses for aprepitant/fosaprepitant?
Chemo induced N and V in combo with 5HT3 antagonist and dexamethasone
32
Side effects for aprepitant/fosaprepitant?
- -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
Antihistamine drug names
- -Dimenhydrinate - -Diphenhydramine - -Meclizine
34
Antihistamine (H1) MOA
- -Sedation | - -H1 may not be primary mechanism, may be anti-muscarinic
35
Antihistamine side effects
- -Anticholinergic (confusion, dry mouth etc,) - -Drug interactions w/ some antibiotics - -Don't use during pregnancy
36
Dopamine receptor antagonist names
- -Droperidol - -Metoclopramide - -Prochlorperazine - -Promethazine - -Thiethylperazine
37
Dopamine receptor antagonists
- -Receptors in CTZ zone - -May have muscarinic antagonism? - -"Reseting" GI motility - -Sedation
38
Cannabinoid names
Dronabinol | Nabilone
39
Side effects of cannabinoids
- -Euphoria - -Sedation - -Hallucinations - -Dry mouth - -Increased appetite (good for cancer patients)
40
What are cannabinoids often given with?
Phenothiazines
41
Corticosteroid MOA in vomiting
Unknown
42
Corticosteroids
Dexamethasone, methylprednisolone
43
What are corticosteroids used with?
5HT3 antagonists and aprepitants