Decontamination agents and Antiemetics Flashcards
Sensory receptor zone
–Especially in the stomach and small intestine, the pharynx, and the inner ear; visual, olfactory, and painful stimuli that can also elicit vomiting
Chemoreceptive trigger zone (CTZ)
- -Located in area postrema, on floor of 4th ventricle.
- -OUTSIDE THE BBB.
- -Primary region for detection of blood-borne emetics
Vomiting center
- -Connected to chemoreceptive trigger zone
- -Located in medulla
- -Responsible for initiation and coordination of complex motor patterns needed for vomiting.
“Higher centers”
Responsible for memory, fear, dread, and anticipation
3 major stimuli that activate the vomiting center
- -Mechanical and/or painful stimuli (esp. in inner ear, local GI irritation, pharynx)
- -Blood borne emetics
- -Higher centers
How does local GI irritation trigger the vomiting center
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
How does the gag reflex trigger the vomiting center?
Glossopharyngeal and trigeminal afferents–> solitary tract nucleus–> vomiting center
What are the chemoreceptive trigger zone receptors?
- -Serotonin
- -Histmine
- -Muscarinics
- -Opioids
- -Dopamine
Serotonin receptor locations
- -GI tract* (primary)
- -Chemoreceptive trigger zone
- -Inside BBB
Dopamine receptor locations
- -GI tract
- -CTZ*
- -BBB
Muscarinic receptor locations
- -GI tract
- -CTZ
- -BBB*
Histamine receptor locations
Inside BBB
NK1 receptor locations
Inside BBB
Cannabinoid receptor location
Inside BBB
Opioid receptor locations
- -GI tract
- -CTX*
- -BBB
Activated charcoal
- -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
Polyethylene glycol-electrolyte solution
- -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
IPECAC
- -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
Antiemetics
- -Gen. more effective at preventing vomiting than stopping emesis once it has started
- -Often used in combo because they act synergistically
Serotonin (5HT3) Anagonists
- -Dolasetron
- -Granisetron
- -Ondansetron
- -Palonosetron
Serotonin (5HT3) antagonist MOA
- -Blockade peripheral 5HT3 receptors on primary afferents
- -Also in CTZ and vomiting center
Therapeutic uses for serotonin antagonists
- -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
Are serotonin antagonists effective for motion sickness?
No
Side effects of serotonin antagonists
- -Well tolerated with good safety profiles
- -Most side effects transient
- -Constipation, dizziness, mild headache
- -Small QT elongation, but not clinically relevant
