6 - GI Flashcards
Three factors that stimulate production of HCl at the parietal cell:
- Acetylcholine (parasympathetic)
- Histamine
- Gastrin
What is the protective substance for the lumen of the stomach:
Prostaglandin E1, E2, and I2 (Prostacyclin)
Meds for mild GERD (<1 episode per week):
Start with H2 inhibitors in addition to antacids for breakthrough symptoms
If not controlled after 4 weeks, switch to PPI
Meds for frequent GERD (> 1 episode per week):
Start with PPI (30-60 mins before meal)
Causes of PUD:
- H. Pylori
- NSAID’s
- Stress Ulcers
- ZES
S/S of gastric ulcer:
Epigastric pain exacerbated by eating
Heartburn, belching, nausea
S/S of duodenal ulcer:
Epigastric pain, usually worse at night, occurs 1-3 hrs post-prandial (pain may actually be relieved by eating)
Heartburn, belching, nausea
All patients with PUD should be tested for:
H pylori
Tx for h pylori:
- Anti-secretory (PPI)
2. ABX (see next card)
1st line triple therapy for H pylori:
- Clarithromycin
- Amoxicillin
- PPI
2nd line quadruple therapy for h pylori:
- Tetracycline
- Metronidazole
- Bismuth subsalicylate
- PPI
How long does for h pylori abx?
14 days
If PUD is present, continue PPI for ___ weeks so ulcers have time to heal (h pylori tx)
4 to 8 duodenal
8 to 12 gastric
Must be off PPI for how many weeks prior to confirmation of eradication test for h pylori?
1 to 2 weeks
Which COX is more important for GI health?
COX-1
If your pt has an NSAID-induced peptic ulcer and they just HAVE to be on an NSAID, consider putting them on:
Celecoxib (Celebrex) - it’s COX-2 selective, so less GI effect (but it DOES come with CV risk)
Prevention of stress ulcers for ICU pt’s:
PPI
H2RA
Clinical indication for antacids:
1st line therapy for intermittent symptoms (less than twice weekly)
Breakthrough therapy for those on PPI or H2RA therapy
Sodium bicarbonate - MOA:
Reacts with HCl to produce carbon dioxide and sodium chloride
CO2 results in gastric distention and belching, but relieved acidity-symptoms
Calcium carbonate - MOA:
Less effective but same MOA as bicarb
Magnesium Hydroxide - MOA:
Reacts slowly with HCl to form magnesium chloride and water
Magnesium hydroxide - clinical use:
Antacid
Laxative
Magnesium hydroxide - AE’s:
Osmotic diarrhea
Magnesium hydroxide is commonly combined with what two drugs to normalize bowel function?
Aluminum hydroxide and simethicone
Histamine (H2) Receptor Antagonists (RA) - H2RA - MOA:
Competitively blocks the binding of histamine to H2 receptors of the parietal cell, inhibiting gastric acid secretion induced by histamine
H2RA’s - clinical use:
PUD
GERD
Dyspepsia
ZES
H2RA’s - AE’s?
CNS effects - HA, dizziness, fatigue, somnolence, confusion
Rare side effect of prolonged use of Cimetidine?
Gynecomastia
Common H2RA’s:
- Cimetidine (Tagamet)
- Ranitidine (Zantac)
- Famotidine (Pepcid)
- Nizatidine (Axid)
What is the preferred H2RA for IV use?
Ranitidine (Zantac) (remember RANitidine - RAN the fluid through the IV)
What are the most effective agents for management of GERD?
PPI’s
All the PPI drug names end in:
Prazole
PPI - MOA:
PRODRUG
Irreversibly binds to the H+/K+ ATPase enzyme system (proton pump) of the cells suppressing secretion of hydrogen ions
PPI - clinical use:
PUD
ZES
GERD
Better than H2RA’s across the board
Should be given 30-60 mins before meals
Adverse effects of PPI’s:
Hypomagnesaemia
C-diff
Risk of fracture
Sucralfate - MOA:
Covers the ulcer site and protects it from acid
Stimulates prostaglandin release
Sucralfate - clinical use:
Heals peptic ulcers, but not seen a lot bc H2RA and PPI are more effective
Misoprostol - MOA:
Prostaglandin analog
Antisecretory and mucosal protective properties
Misoprostol - clinical use:
NSAID-induced ulcers
Not widely used bc of high AE profile and multiple daily dosing
Misoprostol - pregnancy cat:
X
Bismuth Subcitrate Potassium is only available as a combination rx product that contains:
Metronidazole
Tetracycline
(Tx of h. Pylori)
AE’s of Bismouth subsalicylate:
Harmless blackening of stool
Darkening of tongue
High doses can lead to salicylate toxicity
Metoclopramide (Reglan) - MOA:
Dopamine antagonist
Stimulates gastric motility
Block serotonin receptors in the trigger zone, resulting in anti-emetic action
Metoclopramide (Reglan) - clinical use:
GERD
N/V from chemotherapy
Diabetic gastroparesis
Metoclopramide (Reglan) - AE’s:
Extrapyramidal effects (dystonias, akathisia, parkinsonian features
Eryhthromycin - MOA:
Stimulates motilin receptors on GI smooth muscle
Erythromycin - clinical use:
IV - gastroparesis
5HT3 antagonists - MOA:
Block presynaptic serotonin receptors on sensory vagal fibers in gut wall as well as block central blockade in the vomiting center and CTZ
5HT3 antagonists - clinical use:
Post-operative n/v
Chemo and radiation induced n/v
General medical use
5HT3 antagonists - AE’s:
MC is dizziness, HA, constipation
QTc prolongation (uncommon)
5HT3 antagonist drugs:
Odansetron (Zofran)
Granisetron (Kytril)
Dolasetron (Anzemet)
Polanosetron (Aloxi)
Antihistamines - MOA (nausea/vomiting):
Block H1, prevent vomiting due to motion sickness
Causes drowsiness and anticholinergic effcts
Antihistamine meds:
Meclizine
Diphenhydramine
Dimenhydrinate
Doxylamine
Antihistamine - pregnancy cat:
A
Phenothiazines - MOA:
Block dopamine, muscarinic, and histamine receptors in CTZ
Phenothiazines - clinical use:
Effective oral, injectable, and rectal anti-emetics
Phenothiazines - AE’s:
HOTN, extrapyramidal, drowsiness
Prochlorperazine (Compazine) used to be used for:
Typical antipsychotic
Promethazine (Phenergan), although categorically a Phenothiazine, is also a:
1st generation anti-histamine
Scopolamine - MOA:
Cholinergic antagonist - blocks the muscarinic receptors in the vestibular system
Droperidol - MOA:
Blocks dopamine receptors in CTZ
Droperidol - clinical use:
Post-operative n/v
Sedation in endoscopy (in combination with benzos)
What are the two corticosteroids used in tx of n/v?
Dexamethasone
Methylprednisolone
Benzodiazepines - clinical use in n/v?
Reduce anticipatory nausea and vomiting caused by anxiety
Tx for mild diarrhea:
Rehydration fluids
Lactose-free diet
Avoid caffeine
Tx for moderate diarrhea:
Anti-motility agents
Rehydration fluids
Tx for traveler’s diarrhea:
Fluoroquinolones
Azithromycin
Rifaximin
Loperamide - MOA:
Mu opioid agonist
Does not cross BBB
Meperidine derivative
Osmotic laxatives - MOA:
Rapid movement of water into distal small bowel and colon
Leads to bowel distention and passage of stool
Osmotic laxatives - AE’s:
Black box: nephropathy potential (sodium phosphate “fleets”)
Mag-sulfate -> caution in renal patients
Lactulose is preferred as laxative in which pt’s:
Liver disease
What is polyethylene glycol used for?
Colonoscopy prep
Peg 3350 (Miralax) is approved for:
IBS-C
Safe in renal and hepatic disease
Safe in pregnancy
What are the two natural plant fibers used in bulk-forming laxatives?
Psyllium
Wheat dextrin
What are the two synthetic plant fibers used in bulk-forming laxatives?
Calcium polycarbophil
Methylcellulose
Senna - MOA:
Active ingredient = sennosides
Causes water and electrolyte secretion into the bowel
Bisacodyl (Dulcolax) - MOA:
Directly acts on nerves in the mucosa of the colon
Castor Oil - pregnancy?
Contraindicated - will stimulate uterine contractions
Docusate - MOA:
Softens the stool permitting water and lipids to penetrate
Docusate - clinical use
Preferred as prophylaxis rather than acute tx for constipation
Lubiprostone - MOA:
Stimulates secretion of chloride-rich fluid into the lumen
Lubiprostone - clinical use:
IBS-C
Opioid-induced constipation
What color are fire trucks?
“I’ve seen ‘em yellow, blue, red, orange, pink, teal, salmon, and white. Every color of the rainbow.”
-Know it all fire fighter
