Unit 6: GI Flashcards
Vomiting center is rich in
Dopamine, histamine, serotonin, and Ach receptors
Can also be effected by binding to opiate/benzo receptors
Stimulatory nausea center
Chemo trigger zone
most important for sensing noxious stimuli–it is exposed to both the blood and the CSF
Rich in neurotransmitter receptors for dopamine, serotonin, histamine, ACh, and NK (Anti emetic effect occurs when these receptors are blocked)
Phenothiazines
Prochlorperazine + Promethazine
Dopamine receptor blockade in chemo trigger zone
Also has anticholinergic activity
Used as monotherapy for mild-moderate N/V
SE of phenothiazines
EPS may occur due to dopamine blockage
Drowsiness and sedation
Antihistamines and anticholinergics for N/V
Hydroxyzine, meclizine, dimenhydrinate, scopolamine
Used for mild nausea such as motion sickness
Interruption of visceral afferent pathways that are responsible for N/V
Can be used in pregnancy but not breastfeeding
Benzodiazepines for nausea
Prevent and treat emesis as well as anti anxiety and amnesia
Helpful for anticipatory nausea and vomiting with chemo
Lorazepam (ativan) most frequently used
Serotonin antagonists for nausea
Ondansetron (zofran), granisetron, palonesetron, dolasetron
Antagonist 5HT-3 receptors centrally in CTZ and peripherally at vagal and splanchnic afferent fibers
Usually used for chemo N/V
Metoclopramide
Reglan
Highly useful in treatment of diabetic gastric stasis, postsurgical stasis and GERD
Increase motility and gastric emptying by increasing duration and extent of esophageal contractions, resting tone of LES, and gastric contractions
Dopamine receptor inhibition
Used for prevention/tx of chemo N/V
SE of metoclopramide
Can cause increased EPS
Can cause hypertensive crisis when used with MAOI
Corticosteroids for nausea
Reserves for chemo induced N/V
Inhibits prostaglandins
Dexamethasone + Methylprednisolone most common
Usually used in combo with other anti emetics
Cannabinoids for nausea
Only indicated for chemo N/V
Dronabinol is available agent
Effects on vomiting center, opiate receptors in CNS and cerebral cortex
Antacids for nausea
Mild N/V
Coats stomach with neutralizing agent
CaCO3, MgOH, AlOH, AlCO3
First line treatment for non-chemo induced N//V
Phenothiazine
First line treatment for chemo acute emesis
Combo of serotonin antagonist and corticosteroid 30 minute prior to chemo
First line treatment for chemo delayed emesis
Metoclopramide + Dexamethasone
Drug choices for GERD
Antacids, histamine 2 receptor antagonists, proton pump inhibitors
What stimulates parietal cells to release acid
Histamine, ACh, gastrin
What decreases gastric acid production
Prostaglandins and bicarb
Also increase mucus production–GI protective
H Pylori cause of PUD
Increases acid production, increases gastrin secretion and releases its own noxious enzymes and toxins
NSAIDs cause of PUD
Inhibit COX which decreases production of prostaglandins
Antacids
CaCO3, Mg salts, Al salts
Used for mild and intermittent symptoms
Partially neutralize HCl in stomach; pepsin is inhibited
H2 receptor antagonists
Cimetidine, famotidine, nizatidine, ranitidine
Effective in mild GERD, ulcer healing, H pylori eradication
Reversibly inhibits histamine 2 receptors on gastric parietal cells causing decreased acid secretion and pepsin activation
Proton pump inhibitor
Most potent acid-suppressing agents available
-Prazole
Inhibit gastric proton pumps located on parietal cells; produces long suppression of acid secretion
Tx to eradicate H Pylori induced PUD
Antibiotics + acid suppressing medication
Most common antibiotics for H Pylori
Amoxicillin, Carithromycin, Metronidazole, Tetracycline, Misoprostol, Sucralfate, Bismuth Subsalicylate
Algorithm for GERD tx
Lifestyle changes –> H2 receptor antagonist –> if no improvement Proton pump inhibitor–> if no improvement, refer to gastroenterologist
First line therapy for H Pylori eradication
Triple therapy:
- PPI
- Amoxicillin
- Clarithromycin
OR
- PPI
- Metronidazole
- Clarithromycin
Sequential therapy for H Pylori eradication
-PPI
-Amoxicilln
Followed by
-PPI
-Clarithromycin
-Metronidazole
What drugs have shown efficacy for preventing NSAID induced ulcers
PPIs and misoprostol
Bulk forming laxatives
Methylcellulose, psyllium, polycarbophil, malt soup extract, wheat dextrin
Bind to fecal contents and pull water into stool–softens and lubricates stool
Preferred treatment of constipation
Hyperosmotic laxatives
Lactulose, sorbitol, polyethylene glycol, glycerine
Increase concentration of solutes which creates osmotic pressure and draws fluid into intestinal lumen
Saline laxatives
MgOH, Mg citrate, Mg sulfate, Na phosphate, Na biphosphate
Draw water into the intestines through osmosis
May cause dehydration
Stimulant laxatives
Bisacodyl + Senna concentrates
Increase peristalsis through direct effects on smooth muscle of intestines + promote fluid accumulation in colon and small intestines
Avoid long term
Surfactant laxatives
Docusate sodium + Docusate calcium
Decrease surface tension of liquid contents of bowel–promotes incorporation of additional liquid into the stool (stool softener)
DOC in patients who should not strain
Lubricant laxatives
Mineral oil coats and softens the stool and prevents reabsorption of water from the stool by the colon
Lubiprostone
Secretagogues
Derivative from prostaglandin
Increases chloride rich intestinal fluid without altering serum sodium and potassium concentrations
Naloxegol
Peripherally acting mu-opioid receptor antagonists
Decrease constipation of opioids
Does not cross bbb
First line therapy for all forms of constipation
bulk forming laxative
First line therapy if straining should be avoided
Stool softener
First line therapy for constipation in infants
Glycerin
Second line therapy for constipation
Milk of magnesia, lactulose, sorbitol
Third line therapy for constipation
Stimulant laxatives
Meds that might cause diarrhea
Antacids containing Mg, antibiotics, SSRIs, cholinergic agents, cholchicine, digoxin, metoclopramide, laxatives, metformin, prostaglandins, quinidine
Osmotic diarrhea
Nonabsorbed solutes retained in the lumen of intestinal tract–pulls water and ions into intestinal lumen
Secretory diarrhea
Colonic absorption of fluid is secondary to active transport of Na+ through Na/K ATpase
Exudative diarrhea
Inflammation of mucosa
Due to enteritis, UC, carcinoma
Prophylactic agents for travellers diarrhea
Bismuth subsalicylate (pepto bismol) or quinolone antibiotic or rifaximin
Antimotility drug for diarrhea
Loperamide (immodium) and Diphenoxylate
Opioid receptor agonist acting on mu receptors of large intestine
Avoid in patients with infectious diarrhea–fever, bloody stools, fecal leukocytes
Atypical antidiarrheals
Bismuth subsalicylate (Pepto Bismol) Stimulates prostaglandin, mucous and bicarb secretion in stomach and inhibits prostaglandin and chloride secretion in large intestine
Rifaximin
Semi synthetic antibiotic
Only active against noninvasive strains of E. Coli
Blocks transcription of bacteria–alters growth of bacteria
Used for travellers diarrhea
First line tx for diarrhea
Loperamide or rifaximin
Second line tx for dirrhea
Adsorbents/anti secretory
Third line tx for diarrhea
Diphenoxylate
Drug therapy for IBS
Depends on if it is constipation predominant or diarrhea
Antispasmodics for IBS
Dicyclomide Hcl and Hyosycamine sulfate
Direct relaxation of smooth muscle component of GI tract
Serotonin 3 receptor antagonists for IBS
Alosetron
Decrease abdominal pain, slow colonic transit time, increase rectal compliance and improve stool consistence
Used for severe diarrhea with no constipation
First line IBS tx for constipation
Linaclotide or lubiprostone
First line IBS tx for diarrhea
Loperamide
First line IBS tx for bloating and pain
Dicyclomine
Treatments for inflammatory bowel disease
aminosalicylates, corticosteroids, immunosuppressive agents, antibiotics, and biological agents
Aminosalicylates
Sulfasalazine, mesalamine, olsalazine, balsalazide
Gold standard for tx of mild to moderate CD or UC
Decrease inflammation in GI tract by inhibiting prostaglandin synthesis which decreases inflammatory mediators
Aminosalicylates CI in
Patients with aspirin allergy or G6PD deficiency
Corticosteroids for IBD
Prednisone, methylprednisolone, hydrocortisone, dexamethasone, budesonide
Used to treat acute IBD exacerbations only
Immunosuppressive agents for IBD
Azathioprine, 6-mercaptopurine, methotrexate, cyclosporine
Used as adjunct tx to induce or maintain remission
What antibiotics are desirable for IBD
Acts against G- and mycobacterium with low SE profile and poor systemic absorption
Mild to moderate active CD responds to what antibiotics
Metronidazole and Ciprofloxacin
Long term use of metronidazole is associated with
Neurotoxic effects
Biologic agents for IBD
TNF-alpha inhibitors: infliximab, adalimumab, certolizumab
Selective adhesion molecule inhibitors: natalizumab, vedolizumab
First line tx for mild to moderate active luminal CD
Oral aminosalicylates alone or in combo with antibiotic
Oral preferred over rectal
First line tx for moderate to severe CD
Combo of aminosalicylates and corticosteroids
First line tx for mild UC
Aminosalicylates (oral + rectal combo)
First line tx for moderate UC
Add in a corticosteroid to aminosalicylates
Aminosalicylate of choice for IBD
Mesalamine
Corticosteroid of choice for IBD
Oral budesonide
Cyclosporine for IBD
Reserved for acute treatment of severe UC exacerbations
