Gastrointestinal Flashcards
What are the 3 receptor types of the parietal cell that act to stimulate acid secretion through K+/H+ ATPase?
Histamine
Gastrin
Acetylcholine
What are 3 ways gastric epithelial cells protect themselves from the acidic environment?
Secrete mucus
secrete bicarb
mucosal blood flow
Which class acts to neutralize acid and promote healing in the treatment of ulcers and GERD? What are 4 agents in this class?
Antacids: Calcium carbonate (Rolaids, Tums) Sodium bicarbonate Magnesium hydroxide, magnesium carbonate (Maalox, Mylanta) Aluminum hydroxide
Which antacid is rarely used due to induced systemic alkalosis?
Sodium Bicarbonate
Which antacid agent can produce intoxication in the presence of renal disease? What agent should be used instead for pts with renal failure?
Magnesium hydroxide - Mg intoxication in renal disease
Aluminum hydroxide - useful in renal failure pts (not absorbed)
Which antacid agent can cause “rebound” acidity? What are its other adverse effects?
Calcium carbonate
–> Milk-alkali syndrome, nephrocalcinosis, digitalis antagonism, constipation
What are some adverse effects of aluminum hydroxide?
Phosphate depletion and sequelae (weakness, anemia, tetany, apnea); constipation
What are the 3 classes of agents that decrease gastric acid production?
H2 blockers
Anticholinergic agents
H+/K+ proton pump inhibitors
What are 3 anticholinergic agents that reduce acid secretion and prevent spasms? Contraindications?
Atropine sulfate
Propantheline (Pro-Banthine)
Metantheline bromide
–>Contraindications: known pyloric obstruction, hiatal hernia, or peptic esophagitis=reflux esophagitis (not used much)
Name 4 H2 blockers. Mechanism and use?
Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pepcid)
Nizatidine (Axid)
- -> decrease basal and meal acid secretion (doesn’t need to be administered with meals)
- -> Inhibit 50-80% of 24 hour acid production
- -> Ulcer treatment; prophylactically for stress ulcers; GERD
What is a concern if Famotidine is stopped suddenly after prolonged use?
Rebound acidity
–>exaggerated response to histamine
(need to reduce dose slowly)
Cimetidine and ranitidine will do what to warfarin and lidocaine plasma levels?
increase
inhibits P450
What class of drugs will not work if taken with antacid or H2-blocker?
Proton Pump Inhibitors
require acidic environment to activate
What is the mechanism, use and side effects of Lansoprazole?
(H+/K+ ATPase inhibitor)
MECH: Non-competitive Inhibition >90% of 24 hour acid secretion (better than H2 antagonists)
USE: Ulcer treatment, H. pylori; GERD
SE: Headache, gynecomastia, gastric hyperplasia in humans and carcinoid tumors in rats long term (do not use long-term)
Which proton-pump inhibitor has the most P450 inhibition. Which has moderate? Which has NO P450 inhibition?
Most - Omeprazole
Moderate - Rabeprazol
None - Pantoprazole
What are 3 factors that impair mucosal defense?
NSAIDs;
H. pylori;
Zollinger-Ellison syndrome(↑Gastrin)
What is Sucralfate?
Sucrose Sulfate Aluminum Complex
- adjunct to ulcer treatment
- Mechanical protector –> Coats the ulcer crater to promote healing, increases mucosal resistance (requires acid environment)
[Chosen over bismuth salts since it doesn’t turn stool black]
What is the treatment for H. pylori infections?
Triple Therapy:
- PPI or ranitidine 2x a day
- plus 2 of: amoxicillin, clarithromycin, metronidazole
What is the only FDA approved drug for the prevention of NSAID induced gastric ulcers? Mechanism? Use? Contraindications?
Misoprostol (PGE2 analog)
MECH: Decrease acid production, increase mucous and bicarbonate secretion
USE: Ulcer treatment when prostaglandin production decreased (RA patients taking lots of NSAIDs)
CONTRAINDICATION: pregnancy
What is the mechanism and use of Metoclopramide and Cisapride? Which one requires special FDA approval and may cause sudden cardiac death?
MECH: Increase motor tone in lower esophageal sphincter and stomach (promotility/Dopa-blocker)
USE: GERD (w/o esophagitis), gastroparesis, Metoclopramide- anti-emetic
Cisapride- FDA approval/ sudden death (removed from market in July 2000)
What class are Prochlorperazine and Promethazine? Mechanism? Use? SE?
(Phenothiazines)- anti-emetics MECH: Prochlorperazine- Dopamine antagonist Promethazine- H1-blocker, Anticholinergic SE: Prochlorperazine- torticollis Promethazine- somnolence
What is a Benzamide derivate that has an anti-cholinergic mechanism to suppress CRTZ and is given in oral form. SE?
Tetrahydro Cannabinol (THC)
SE- munchies
CRTZ=Chemoreceptor trigger zone
What is the use, mechanism and side effect profile of Ondansetron, Granesitron & Dolasetron? Which one is safe enough for use in infants?
Anti-emetics
5HT3-blockers (serotonin antagonists)
SE: headache, dizziness, somnolence
Ondansetron- very safe
What agent would be used for gastroparesis?
Metoclopramide
taken before each meal to stimulate upper GI motility [no effect on gastric, biliary or pancreatic secretions]
What are 3 classes of drugs used to treat diarrhea? Mechanism of each?
- Anticholinergics- relax bowel smooth muscle
- Opioid Agonists- stimulates μ receptors in GI tract; increased rectal tone leading to segmentation of colon and disruption of peristalsis–> increased absorption time
- Colloids/Pectins- absorb water to bulk stool (do NOT prevent dehydration)
What is the use of atropine sulfate for GI disorders?
Anti-cholinergic - treatment of diarrhea
can be combined with opioid agonists
Name 3 opioid agonists used in the treatment of diarrhea. Contraindication?
Loperamide (Immodium)
Diphenoxylate (Lomotil)
Codeine sulfate
-The last 2 are contraindicated in children (respiratory suppression)
Name a colloid. Name a pectin.
Metamucil - colloid
Kaopectate (Bismuth subsalicylate) - pectin
What is the use and mechanism of: Castor oil Cascara sagrada senna extract Bisacodyl phenolphthalein
- irritant/stimulant used for constipation
- Irritate lumen of the colon, causes peristaltic contractions
What is the mechanism and 2 uses of:
Magnesium citrate; Magnesium sulfate (Epsom salt); sodium sulfate (Glauber salt); Milk of Magnesia
-Osmotic cathartics–> Draw water into the colon
USE: Constipation; clean bowel prior to colonoscopy
What is the use and mechanism of: Psyllium seed (Metamucil); methylcellulose (Hydrolose); sodium carboxymethylcellulose
Bulk-forming hydrophilic colloid
USE: Constipation (especially small, hard stools)
What is the use and mechanism of:
Mineral oil; Dioctyl sodium sulfo-succinate (Colace); poloxalkol
Stool softening, lubrication for constipation
Name 3 agents used to treat Ulcerative Colitis. Mechanism?
Sulfasalazine
Olsalazine
Mesalamine
Work from lumen to reduce inflammation
Name 4 agents used for chronic treatment of Ulcerative Colitis. Mechanism of each?
Prednisone- Corticosteroid
Azathioprine- Purine antimetabolite
Cyclosporine- suppresses T cells
Infliximab (Remicade)- Binds and neutralizes TNFa
What is the use and mechanism of Dicyclomine HCl & Hyoscyamine sulfate
Anticholinergic (antispasmodic)
Reduce spasm in irritable bowel syndrome
Alosetron and Tegaserod maleate are 2 agents whose approval has been withdrawn by the FDA. What are they used to treat and what’s the difference between them?
-Irritable Bowel Syndrome
Alosetron- diarrhea predominant symptoms
Tegaserod maleate- constipation predominant
