PHARM: Overview of GI Pharm Flashcards
Effect of SNS on walls of GI tract. (what receptors)
Relaxes via alpha-2, beta-2 (probably through presynaptic inhibition of parasympathetic activity)
Effect of SNS on sphincters of GI tract. (what receptors)
Contracts via alpha-1 receptors
Effect of SNS on GI tract secretions.
NONE
Effect of PSNS on walls of GI tract. (what receptors)
Contracts via M3 receptors
Effect of PSNS on sphincters of GI tract. (what receptors)
Relaxes via M3
Effect of PSNS on GI tract secretions. (what receptors)
increases via M3
What is the predominant tone of the GI tract?
parasympathetic
What is the major GI side effect of Cholinergic Agonists and Acetylcholinesterase inhibitors?
diarrhea
What are the major GI side effects of muscarinic antagonists?
constipation and decreased glandular secretions
Which type of muscarinic antagonists can cross the BBB? What is the consequence?
tertiary (confusion, delirium, etc.)
What controls the GI system?
enteric nervous system
what are the two components of the enteric nervous system?
Myenteric Plexus
Submucosal Plexus
What is another name for the Myenteric plexus?
Auerbach’s
What is another name for the submucosal plexus?
Meissner’s
What plexus controls contraction and relaxation of the GI smooth muscle?
Myenteric (Auerbach’s)
What plexus is involved with secretory and absorptive functions of the GI epithelium, local blood flow, and neuro-immune activities?
Submucosal (Meissner’s)
What is principle neurotransimtter of the enteric nervous system?
acetylcholine
What is “enkephalin”?
opiod peptide
What do opiod peptides do in the ENS?
inhibit Ach release and peristalsis while possibly stimulating secretion
Other than Ach, what is an important transmitter at the neuron-to-neuron junctions in the ENS?
Serotonin
What receptors does serotonin use in the GI?
5HT-3 and 5HT-4
What type of receptors are D2?
dopamine receptors on muscle
Where are D2 muscular receptors located?
lower esophageal sphincter and the antrum/fundus of the stomach
What are the actions of dopamine on the D2 receptors?
relaxes LES/antum/fundus AND it has indirect inhibitory effect on the musculature of the GI system
How does dopamine indirectly inhibit musculature of the GI system?
inhibiting Ach release from intrinsic cholinergic motor neurons by activating pre-junctional D2 receptors
How can you reverse the dopaminergic inhibition of GI musculature?
giving drug that has anti-domaminergic and serotonergic actions (have pre-junctional excitatory 5-HT4 receptors that will stimulate GI motility)
What drug has a mixed anti-dopaminergic and serotoninergic effect?
Metoclopramide
What does Metoclopramide do?
increase lower esophageal tone and stimulate antral and small intestinal contractions
Which receptors are inhibited by metoclopramide? What are their normal actions that are being inhibited by this drug?
5-HT3 (inhibits Ach release and relaxes SM)
D2 (inhibits cholinergic signals and decreases SM contraction)
Which receptors are stimulated by metoclopramide? What are their normal actions that are sitmualted by this drug?
5-HT4 (stimulates Ach release and SM contraction)
What is the major feature of UC?
disruption of physical barrier
How do you treat UC?
- Glucocorticoids
- Infliximab
- Adalimumab/Golimumab (as indicated)
What is the underlying feature of Crohn’s disease?
microbe sensing dysfunction
How do you treat Crohn’s disease?
- Glucocorticoid/ Immunomodulator
- TNF-alpha mAb’s
What type of inflammatory reaction is seen in IBD?
TNF-alpha mediated
What do the TNF-alpha mAb’s do?
block the interaction between TNF-alpha molecules and the TNF-alpha type 1 and type 2 (and soluble) receptors to neutralize the pro-inflammatory signal and inhibit expression of inflammatory genes
What is a major adverse effect of opiates?
constipation
What should always be prescribed with opiates?
laxative agent (or opiate antagonists)
What is the ONLY mu-specific opiod antagonist?
alvimopan
What are the major pharmacological effects of opiods in the GI?
increase tone, increase absorption, decrease secretions (so constipation and cramping)
True or false: GI tract events are the most common type of preventable adverse drug event in older ambulatory persons
TRUE
What type of diarrhea is caused by: Medications draw water into GI tract
osmotic
What type of diarrhea is caused by: Na+ absorption is impaired and Cl- and HCO3 ions are secreted into the GI lumen (pull in H2O)
secretory
What type of diarrhea is caused by: Drugs affect cholinergic tone
disordered motility
What type of diarrhea is caused by: Disruption of colonic flora precipitating C. difficile colitis or following direct damage of the gastric mucosa. Risk increases with duration of antibiotic exposure or NG tube.
inflammatory
What type of diarrhea is caused by: Disrupting the acid-base environment or epithelial homeostasis
C. difficile diarrhea
What type of diarrhea is caused by: Mal-digestion or absorption by virtue of a drug’s mechanism of action.
steatorrhea (fatty diarrhea)
What type of diarrhea do the following drugs cause: Metformin, antibiotics, anticholinergics, NSAIDs, calcitonin
secretory diarrhea
What type of diarrhea do the following drugs cause: Antibiotics, chemotherapy agents; immunosuppressants; PPIs; TKIs; SSRIs; NSAIDs
Inflammatory diarrhea
What type of diarrhea do the following drugs cause: NSAIDS (direct epithelial damage and changes in Na+ permeability).
C. difficile diarrhea
What type of diarrhea do the following drugs cause: alpha-glucosidase inhibitors
osmotic diarrhea
What type of diarrhea do the following drugs cause: Metformin (decrease glucose absorption); Octreotide; Orlistat (Alli); Cholestyramine
Steatorrhea
What type of diarrhea do the following drugs cause: Cholinergic drugs; macrolides
disordered motility
Why is vancomycin good for treating C. difficile?
it gets very high in concentration in the GI tract (because it does not get absorbed)
What is the name for the condition in which there is a feeling that a pill is stuck in throat +/- burning and retrosternal pain?
pill-induced esophagitis
What is common among risk factors for pill-induced esophagitis?
decreased saliva (ex. old age, anticholinergics)
What pills might give worse proglems with pill-induced esophagitis?
gelatin capsules and extended- or sustained-release products
What two metabolic components are found in the intestinal wall where they modulate bioavailability and participate in the 1st pass metabolism of various drugs?
CYP3A and P-GP
What is P-GP?
energy-dependent pump located in small intestine epithelial cells (kidney, BBB, placenta, etc.) and decreases bioavailability by pumping back into lumen.
What happens when you decrease P-GP?
drug bioavailability will INCREASE (because drug is not being pumped back into lumen)
What may control CYP3A?
P-gp/MDR1
What is the connection between CYP3A and P-gp/MDR1 ?
P-gp/MDR1 works to pump drugs back into the lumen after passive absorption to be presented to CYP3A4 over and over (increasing the change it will be metabolized)
Why do NSAIDs cause gastric ulcers?
decrease PGs and prevent the release of protective mucous by GI epithelial cells
What are the 3 main drug classes for altering acidity?
Antacids
PPIs
H2 Histamine blockers
What is the MOA of antacids?
alter pH and chelate (bind up and prevent absorption of drugs like antibiotics)
What is the MOA of PPIs?
alter pH and inhibit CYP2C19
What ist he MOA of H2 histamine blockers?
alter pH and inhibit CYPs (cimetidine)
What substance has been indicated in the inflammatory response of migraine headaches?
CGRP