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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
- 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.
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
- Chemotherapeutic emesis
- Postoperative nausea and vomiting
- Radiation sickness
- Opioid side effects (they decrease peristalsis.)
- Prevents nausea.
What are the side adverse effects and contraindications of Metoclopromide (Reglan)?
- Extrapyramidal symptoms (Involuntary movement of parasympathetic nervous system).
- Cotton mouth..
- GI obstruction
- GI hemorrhage
- GI perforation
- All conditions are exacerbated by increased peristalsis.
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.
- 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
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.
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.
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)
Seratonin (5HT3) Receptor Antagonist
- 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.
What are some adverse reactions to Seratonin (5-HT3) Antagonist Recpetors?
- Abdominal pain
- Visual disturbances
- Somnolence (sleepiness, loopiness)
- Occassional prolonged QT (heart rhythm) changes
Dopamine Antagonsit Antiemetic Drugs
- Blocks dopamine receptors in the CTZ
- Isn’t effective for motion sickness
- Side effects make it difficult to tolerate
- Extrapyramidial reactions
- Anticholinergic effects
What are the adverse side effects of Dopamine Antagonist Antiemetic drugs like Inapsine?
- Extrapyramidal reactions
- Prolonged QT complex