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What is the action of Prokinetics and when can they be used?
- Increase the tone and motility of the GI tract
- Indications:
- GERD Gastro-esophogeal reflux disease: Encourage stomach contents to move to intestine more quickly.
- Chemotherapy induced nausea and vomiting: Again, move more quickly and thereby decrease nausea.
- Diabetic gastroparesis: Aids motility of stomach contents -->intestine.
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Prokinetic Drugs (Metoclopramide (Reglan)
- Suppresses emesis by blocking receptors for dopamine and serotonin in the chemoreceptor trigger zone (CTZ)of the brain
- Increases upper GI motility by enhancing the action of ACh (Acetylcholine)
- May give in oral or parenteral form
- Uses:
- Chemotherapeutic emesis
- Postoperative nausea and vomiting
- Radiation sickness
- Opioid side effects (they decrease peristalsis.)
- GERD
- Prevents nausea.
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What are the side adverse effects and contraindications of Metoclopromide (Reglan)?
- Sedation
- Diarrhea
- Extrapyramidal symptoms (Involuntary movement of parasympathetic nervous system).
- Cotton mouth..
- Contraindication:
- GI obstruction
- GI hemorrhage
- GI perforation
- All conditions are exacerbated by increased peristalsis.
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General Information about Antiemetics...
- Used to suppress emetic (vomiting) Response.
- Reflex started by activation of the vomiting center in the medulla either directly or indirectly.
- Directly:
- Signals from the cerebral cortex
- Sensory organs
- Vestibular apparatus of inner ear
- Indirectly~ Through stimulation of the chemoreceptor trigger zone (CTZ)
- Receptors~ Serotonin, Dopamine, Acetylcholine and Histamine
- Emetogenic compounds (stuff that makes you puke)– opioids (especially oral), chemotherapy drugs or toxins
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What are 3 types of Emetis?
- Anticipatory ~Triggered by memories
- Acute ~ Occurs 1-2 hours after chemotherapy
- Delayed ~ Occurs a day or more after chemotherapy
- For chemo pt’s, preemptively administer their antiemetic as soon as they arrive because they will likely have anticipatory nausea as soon as they get there.
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Things to consider when treating emetis...
- Antiemetics are more effective in PREVENTING emesis than in suppressing it, so always deal with nausea before it turns into vomitting.
- Nausea is a subjective symptom. Like pain, it is what the pt says it is.
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What is the action of Serotonin Recptor Antagonist Antiemetics?
- Acts by blocking serotonin receptors in the CTZ and on afferent vagal neurons in the upper GI tract
- First line drugs available to relieve nausea from chemotherapy, PONV (PostOp Nausea and Vomiting)
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Seratonin (5HT3) Receptor Antagonist
Ondansetron (Zofran)
- Oral or parenteral forms
- Usually given prior to emetic events
- Can be used for PONV (PostOp Nausea Vomitting)
- Very often used prior to chemo therapy.
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What are some adverse reactions to Seratonin (5-HT3) Antagonist Recpetors?
Ondansetron (Zofran)
- HA
- Constipation
- Diarrhea
- Abdominal pain
- Visual disturbances
- Somnolence (sleepiness, loopiness)
- Occassional prolonged QT (heart rhythm) changes
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Dopamine Antagonsit Antiemetic Drugs
(Inapsine)
General Info
- Blocks dopamine receptors in the CTZ
- Isn’t effective for motion sickness
- Side effects make it difficult to tolerate
- Extrapyramidial reactions
- Anticholinergic effects
- Hypotension
- Sedation
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What are the adverse side effects of Dopamine Antagonist Antiemetic drugs like Inapsine?
- CNS:
- Seizures
- Extrapyramidal reactions
- Sedation
- CV:
- Hypotension
- Tachycardia
- Prolonged QT complex
- Arrythmias
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