GI System from Pharm Perspective Flashcards
What are the receptors for SNS on GI
- wall - relaxed by acting on Alpha 2 and beta 2
2. spincters - contract by alpha 1
What are the receptors for PNS on GI
- contracts walls via M3
- relaxes sphincters via M3
- increases secretions via M3
What will happen w/ ganglionic blockade of PNS
reduced tone and motility; constipation; decreased gastric and pancreatic secretions
What are symptoms of excess cholinergic effects
DUMBELLS
What are the symptoms of cholinergic deficit
Constipation, urinary retention, mydriasis/blurred vision, bronchodilation, tachycardia, antiemesis, decreased glandular secretions, restlessness, confusion, delirium, hallucinations
What is the role of Ach in ENS
primary excitiatory transmitter to SM and secretory cells. Major neuron-neuron transmitter in ENS
What is the role of Dopamine in ENS
modulatoary transmitter in ENS
What is the role of enkephalin and related opioids
present in some secretomotor and interneurons in ENS. inhibits Ach release and peristalsis. May stimulate secretion
What is the role of serotonin
important transmitter or cotransmitter at excitatory neuron-neuron junctions in the ENS
What is being considered for treatment of some IBS cases
Might be related to serotonin disequilibrium. there is excess 5HT in D-IBS. Insufficient release of 5HT for C-IBS.
-giving partial agonists so that you can treat the spectrum of diseases
MOA of Tegarserod
partial 5HT-4 agonists. Withdrawn from market b/c of many heart problems
MOA of citalopram
SSRI
What has been IDed as playing a pivotal role in inflammation of IBD
TNF-alpha. Now using mabs that soak up the TNF-alpha w/ infliximab. This therapy is only started after steroid therapy is unsuccessful
What are the effects of opioid receptors and GI phys
Receptors are found in the ENS. they relieve pain but have a delayed transit effect in the GI causing constipation
What is the MOA of Naloxone and methylnaltrexone
opioid receptors. micro-receptors w/ Beta-endorphin being the ligand. Location of receptors are in both myenteric and submucosal plexus
What is the GI effects of naloxone and methylnaltrexone
delayed transit, visceral antinociception
What are the different forms of drug-induced diarrhea
- osmotic
- secretory
- disordered motility
- inflammatory - due to disruption of colonic flora, disruption of acid-base environment or epithelial homeostasis
Who is an increased risk for pill-induced esophagitis
- old age
- institutionalization
- preexisting esophageal or swallowing disorders
- recumbent position
* gelatin capsules, extended/sustained release products increase risk of this
What are common side effects of pill-induced esophagitis
- constipation
- bleeding, erosions – dont’ forget NSAIDS can do this
- pill esophagitis
What is drug absorption based on
- depends on drug formulation and physiochemical properties.
- absorption can occur throughout the GI tract depending on formulation and local pH
- Pgp interactions - if there is decreased Pgp activity there will be a dramatically increased drug concentration
- CYP3A4 - overlapping role w/ Pgp and cyp metabolism can even be controlled by Pgp
What are some drug interactions of antacids
- chelations especially for antimicrobials such as Doxy, tetra, and most fluoroquinolones.
- can cause constipation or diarrhea and can alkalinze the urine
Drug interactions of H2 blockers
- increase pH - affects many drugs
- Cimetidine - inhibits lots of CYPs affecting many drugs
- Famotidine - decreased theophylline clearance
Drug interactions of PPIs
- all substrates for CYP2C19, all exert some degree of 2C19 inhibition
- decreased effectiveness of clopidogrel (needs 2C19 activation)
- decrease bioavailability of antiretrovirals
