GI Flashcards
Probiotics vs Prebiotics
Probiotic contraindications
Immunocompromised
Goals for anti-diarrheal therapy
- Eliminate causes
- Decrease fluid in lumen
- Decrease propulsive contractions
- Increase mixing contractions
Opioids as anti-diarrheals
Examples and Mechanism of Action
Eg. morphine and codeine
MOA: Mu receptor agonist, work by increasing fluid absorption and decreasing fluid secretion, decreasing propulsive contractions and increasing segmental contractions to delay gastric emptying
Loperamide
Mu opioid agonist with low risk for addiction
Less CNS effects, more PNS
Side effect: fatigue, n/v, dizziness, dry mouth, cramping, paralytic ileus, urinary retention, rash
Bismuth Subsalicylate
Mechanism of Action and Side Effects
Stimulates fluid absorption in GI tract, reduces inflammation by inhibiting prostaglandins, binds to toxins, and bactericidal action
Can cause black stool
Toxicity can lead to tinnitus
Pharmalogical constipation options
- Bulk laxatives
- Emollients
- Stimulants
- Saline laxatives
- Hyperosmolar laxatives
- Enemas
Bulk laxative
Examples and Mechanism of Action
Not systemically absorbed, work by pulling fluid into the GI to form a soft, bulky stool
Eg. Psyllium, methycellulose, calcium polycarbophil, bran
*Must take with plenty of water
Emollient examples and mechanisim of action
Docusate sodium (Colace) and Docusate calcium (Surfak)
Not systemically absorped, work by enabling stool to be penetrated by water and become soft
First line for hard/dry stool
Stimulant laxatives
Examples and mechanism of action
Bisacodyl, Senna, Castor oil
Act on GI mucosa to stimulate peristalsis
Not for long term use, can cause dependence
Saline laxatives
Examples and mechanism of action
Magnesium hydroxide, magnesium sulfate, magnesium citrate, sodium phosphate
Work by drawing water into the intestinal lumen
Hyperosmolar laxatives
Examples and mechanism of action
Lactulose, sorbitol, glycerol, polyethylene glycol
Draws water into the intestinal lumen, doesn’t have electrolytes like saline laxatives do.
Enema examples and mechanism of action
Sodium phosphate (Fleet enema), soap suds, tap water, olive oil, saline
Induce bowel evacuation by stimulating distention
*Risk for electrolyte imbalances with all enema types
Pharmalogical Options for GERD/PUD
- Antacids
- H2RB
- PPI
- Probiotics
- Bismuth
- Antimicrobials
- Cytoprotective agents
Antacids Mechanism of Action and Patient Education
Work by neutralizing gastric acid, thereby increases pH of stomach and duodenum.
Take 1 hour after meal, drink full glass of water with tablet
Antacid adverse effects
Calcium carbonate and aluminums: constipation
Magnesium hydroxide: diarrhea
Sodium bicarbonate: elevated Na+ and fluid retention
Histamine 2 Receptor Blockers
Examples and Mechanism of Action
Ranitidine, Cimetidine, Famotidine, Nizatidine
Binds H2 receptors of gastric parietal cell reducing secretion of gastric acid.
**Considered first line for patients with more than ocassional symptoms
H2 Receptor Blockers Cautions
Generally well tolerated
Use caution in elderly (Beers criteria)
Proton Pump Inhibitors
Mechanism of Action and Examples
Irreversibly bind to hydrogen-potassium ATPase pump of parietal cell to block acid secretion.
Esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole
PPI adverse effects and education
Can have nutrient malabsorption, rebound heartburn with prolonged use
Increased risk for bacterial infection, pneumonia, fracture, CKD, possible increase MI risk
Beers criteria (avoid in elderly >8 weeks)
Take before breakfast, do not take at same time as H2 receptor blocker
PUD Management
- Decrease acid secretion with PPI
- Treat infection if present (H. pylori)
- Cytoprotective agents to protect gastric mucosa
- Remove contributing factors (NSAIDs)
Sucralfate
Mechanism of Action, Patient Education, Side Effects
Creates protective barrier which allows healing of gastric mucosa
Take 2 hours apart from other medications on an empty stomach
Constipation most common s/e
Avoid in renal failure
Misoprostol
Indications, Side Effects, Education
Used for NSAID induced PUD
Side effects: diarrhea, cramping, pain
**Abortifactant: must document effective birth control in persons of childbearing years with uterus. May also cause birth defects and premature birth.**
H. Pylori Therapy
- Bismuth
- Clarithromycin
- Amoxicillin
- Tetracyline
- Metronidazole
Bismuth Quadruple Therapy
- Bismuth
- PPI (omeprazole or pantoprazole)
- Metronidazole
- Tetracycline
Nausea and vomiting neurotransmitters
Main pharm agents for nausea and vomiting
- Antihistamines & Anticholinergics
- Dopamine agonists
- Selective Serotonin Antagonists
Antihistamine/Anticholinergic as anti-nausea/vomiting
Mechanism of Action and examples
Dimenhydrinate, Hydroxyzine, Meclizine, Promethazine, Scopolamine
Block the physiologic action of histamine (H1)/acetylcholine at the receptor site
Interrupts visceral afferent pathways that are responsible for stimulating n/v reflex
Most commonly used in motion sickness
Dopamine antagonists
Mechanism of Action
Centrally acting: inhibiting the dopamine receptors in the medullary chemoreceptor trigger zone
Peripherally Acting: block the vagus nerve in the gastrointestinal tract resulting in stimulation of GI motility
Centrally Acting Phenothiazines
Side effects and contraindications
Promethazine, Prochlorperazine
Side effects: blurred vision, dry mouth, dizziness, restlessness, seizure, extrapyramidal symptoms, tardive dyskinesia
Contraindicated: glaucoma, liver disease, prostate and bladder issues
Peripherally Acting Phenothiazines
Side Effects
Metoclopramide (central and peripheral activity)
Diarrhea, fatigue, QT prolongation, extrapyramidal side effects
**Beers Criteria**
Serotonin (5HT3) Antagonist
Indicatons and Side Effects
Ondansetron
Used in chemotherapy induced n/v, postop, severe n/v, pregnancy
May cause headache, constipation, need to monitor LFTs with prolonged use, QT prolongation, QRS widening
What drugs/classes of drugs can lower lower esophageal sphingter tone increasing risk of reflux?
Anticholinergics
Benzodiazepines
Caffeine
Calcium channel blockers (dihydropyridines)
Estrogen/progesterone
Nicotine
Nitrates
Theophylline
Tricyclic antidepressants
