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Flashcards in Pharm: GI disorders II Deck (20)
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What is the major control network for the GI tract (contraction, secretion, absorption control)?

enteric nervous system


What are the two networks for the enetric system?

myenteric/auerbach plexus: responsible for motor control; found btw muscle layer of GI
submucosal/meisner's plexus: secretory, transport, vascular control


What neurotransmitter is seen in excitatory motor neurons of the GI tract? What neurotransmitter is seen in inhibitory neurons of the GI tract?

excitatory: ACh
inhibitory: NO


What chemical factors contribute to the development of GERD?

content/pH of refluxed fluid
epidermal growth factor activity: can be a cancer risk


What four physical factors contribute to the development of GERD?

1. decr. lower esophageal sphincter pressure
2. anatomical factors like a hiatal hernia
3. decreased esophageal clearance
4. delayed gastric emptying (gastroparesis)


Metoclopramide/reglan. What is the class and gemical structure

dopamine D2 receptor antagonist (substituted benzamine); 5-HT4 agonist


What does dopamine do in the GI tract?

inhibits cholinergic neurons
lowers lower desophageal sphincter pressure


MEtoclopramide/reglan: What is its action? What does it NOT do?

1. incr. lower esophageal tone
2. incr. small intestines contraction
3. some anti-emetic effects
Provides symptomatic relief of GERD symptoms but does NOT heal the esophagus.


What are some side effects of metoclopramide?

sedation, diarrhea, tardive dyskinesia


What is cisapride/propulsid? (chemical structure, type/class, action)

substituted benzamide: serotonin agonist (serotonin incr. movement in GI)
prokinetic treatment for GERD through action on myenteric/auerbach plexus.


What are side effects of cisapride/propulsid?

cardiac arrhythmia, sudden death, long QT syndrome. esp. seen in pts taking other drugs metabolized by CYP3A4 or with certain polymorphisms
not used here except as a very last experimental resort; must monitor with EKG


What are the 4 types of laxatives?

luminally active bulking agents
stool softeners
prokinetic agents


How do different kinds of luminally active bulking agents work (3)?

1. hydrophilic colloids: absorb water to incr. stool bulk and stimulate GI motitily
2. saline cathartics: indcue osmotically mediated water retention
3. lactulose: disaccharide- aslo acts as an osmotic laxative


What is loperamide? How does it work (simple)?

trade name imodium
inhibit ACh release through mu opiod receptors
treats diarrhea


3 phases of emesis

1. pre-ejection phase (gastric relzxation)
2. retching phase (rhythmic contractions)
3. ejection phase (intesne contractions and relaxed upper esophageal sphincter)


From what 4 areas does the emesis center receive input?

1. chemoreceptor trigger zone, which monitors blood and CSF for toxic substances
2. cerebral cortex, which mediates vomiting associated with emotional disturbances
3. cerebellum/vestibular system, which mediates motion sickness
4. solitary tract nucleus (STN)/vagus nerve and splanchnic afferents, which mediates vomiting due to GI irritations


What is ondasetron (Zofran)?
(drugs in this class end in -etron)

5-HT3 receptor antagonist (serotonin receptor antagonist)
interfere with input from the chemoreceptor trigger zone and solitary tract nucleus into the emesis center
treat many causes of vomiting, but not vomiting due to motion sickness.


What 5-HT3 (serotonin) receptor antagonist that works as an anti-emetic should I know?



What is chlorpromazine (thorazine)? uses? sides?

dopamine receptor antagonist; phenothiazines structure.
helps a little with chemo-induced vomiting
sides: hypotension, extrapyramidal symptoms


What drugs should be used to treat vomiting caused by motion sickness?

antihistamines (H1 receptor antagonists)
promethazine (phenegran) is the one we need to know
also diphenhydramine (benadryl) and diphenhydrinate (dramamine)