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antacids, H2 antagonists
GI
42
Medical
Graduate
08/23/2010

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Term
what is the etiology of peptic ulcer disease?
Definition
primary: helicobacter pylori. also: NSAIDs, increase of destructive factors (HCl, pepsin, bile), and decrease in defensive factors (mucus, HCO3, blood flow/NO, regeneration or growth factors) or increase in aggravating factors (ethanol, diet, smoking, stress, steroids, NSAIDs)
Term
what % of GI ulcers is helicobacter responsible for?
Definition
70% however - many pts with helicobacter pylori infections also have cachexia - so they never get an ulcer, just accompanying gastritis
Term
why is stress a contributing factor to peptic ulcer formation?
Definition
b/c stress increases HCl secretion and decreases immune function
Term
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Definition
Term
what generally characterizes the antihistamine H2 blockers? are their effects dose-dependent? what kind of acid secretions do they inhibit? what location ulcers are they effective against? do they have an effect on GI motility/emptying time? what is their healing rate?
Definition
the H2 blockers such as *cimetidine are competitive receptor antagonists, they have dose-dependent effects, inhibit basal/food-stimulated/nocturnal acid secretions, effective for duodenal > gastric ulcers, have little effect on GI motility/emptying time and have a healing rate of > 70% are completely healed w/in 6-8 wks
Term
what was the first H2 blocker?
Definition
cimetidine
Term
how is cimetidine metabolized? does it interact with other drugs? how does it affect hormones? can pregnant women use it?
Definition
cimetidine undergoes 1st pass metabolism and will inhibit the P450 enzyme system - therefore it interacts with diazapems, anticoagulants, etc. cimetidine also blocks the androgen receptor and decreases the metabolism of estradiol/increases prolactin levels, leading to gynecomastia and impotency in men and galactorrhea in women. it is not recommended during pregnancy.
Term
other than cimeditine, what are the other H2 blockers and any particular characteristics?
Definition
ranitidine (minimal P450 inhibition), famotidine (negligible P450 inhibition), and nizatidine (negligible P450 inhibition)
Term
what are the ADRs for H2 blockers?
Definition
H2 blockers are generally safe, w/only moderate, reversible ADRs including: rash, GI disturbances, diarrhea, CNS (drowsiness, confusion, *headache*, malaise, dizziness), bradycardia/hypotension w/ rapid IV admin, alteration of liver function/enzyme productio, and hormonal effects *only for cimetidine*:impotency, gynecomastia, and galactorrhea
Term
what is the level of drug-drug interaction with H2 blockers?
Definition
drug interaction w/H2 blockers is mostly relegated to cimetidine b/c of its P-450 activity (esp w/benzos, phenytoin, warfarin), but also decreased absorption of drugs which require GI acidity (ketoconazole/itraconazole), and antacids - which decrease absorption of H2 blockers.
Term
what drugs are the most effective in reducing HCl secretion? what is their mechanism of action?
Definition
proton pump inhibitors which *irreversibly inhibit H+/K+ ATPase* such as omeprazole, esomeprazole, lansoprazole, pantoprazole, and rabeprozole
Term
what conditions are proton pump inhibitors used for?
Definition
zollinger-ellison syndrome (gastrin-tumors), gastric/duodenal ulcers, and GERD
Term
what ADRs are associated with proton pump inhibitors?
Definition
P450 inhibition (w/omeprazole), headache, rash, increased liver enzymes (like cimetidine), GI disturbances like diarrhea, hypergastronemia, rat carcinoid tumors, reduced Ca++ absorption (*risk of osteoporosis), and colonic cell hyperplasia
Term
how should proton pump inhibitors be administered?
Definition
on an empty stomach and all undergo 1st pass metabolism
Term
what are long term risks of GI acid suppression (hypochlorhydria)?
Definition
increased gastric CA, helicobacter pylori overgrowth, gastronemia, rebound hyperacidity, polyps, and decreased B12 and iron absorption
Term
how do H2 blockers compare with PPIs?
Definition
PPIs are *better with H. pylori infection, *hemorrhagic ulcers/bleeding - maintain clot better w/pt on NSAIDs. H2 blockers have a lower incidence of ADRs, they are *cheaper, *safer in pregnancy (except cimetidine), cause *less hypergastrinemia and *potential for gastric carcinoid tumors
Term
what is sucralfate?
Definition
a cytoprotective salt of sucrose complexed to sulfated aluminum hydroxide which interacts with HCl to form a viscous paste that binds to proteins in ulcers or erosions. it is also supposed to increase mucosal prostavglandin synthesis
Term
what ADRs are associated with sucralfate?
Definition
n/v, *constipation
Term
does sucralfate interact with other drugs?
Definition
sucralfate interacts (esp during absorption) with digoxin, anticoagulants, phenytoin, and quinolones and *SHOULD NOT* be administrated with antacids, H2 blockers or PPIs
Term
what is misoprostol? what does it do? when is it used?
Definition
misoprostol is a synthetic prostaglandin E1 analog that replaces the protective prostaglandins consumed with prostaglandin-inhibiting therapies such as NSAIDs. misoprostol increases mucus/NO/HCO3, increases cell proliferation, decreases acid secretion, preserves microcirculation, and stabilizes lysosomes.
Term
what ADRs are associated with misoprostol?
Definition
diarrhea, gas, cramps, stimulation of GI and uterine smooth muscle - *contraindicated in pregnancy*
Term
what is bismuth subsalicylate?
Definition
peptobismol is a colloidal preparation of bismuth (heavy metal - not absorbed) and salicylate (absorbed)
Term
how does bismuth subsalicylate work?
Definition
bismuth subsalicylate binds mucus glycoproteins, coats/protects GI from pepsin/bile acids, increases mucus/HCO3, PG synthesis, decreases intestinal secretions, and is bacteriocidal to E. coli, H. pylori, C. difficle, and B. fragilis
Term
what ADRs are associated with bismuth subsalicylate?
Definition
bismuth subsalicylate may stain teeth, GI mucosa, and blacken stools due to bacterial interaction to form bisulfide. w/overusage, bismuth toxicity (encepthalopathy) and salicylate toxicity are possible
Term
if H. pylori is confirmed/suspected in conjunction with a peptic ulcer, what antibx are effective? are there any drugs that increase the efficacy of these antibx?
Definition
pepto-bismol, metronidazole, tetracycline, amoxicillin, clarithromycin. PPIs will increase intragastric pH which then increases the action of these antibx - esp amoxicillin
Term
what are the options for tx of GERD (gastro-esophageal reflux disease)?
Definition
lifestyle modification, prokinetic agents, acid suppression, and antireflux sx
Term
what is the main prokinetic drug used for tx of GERD?
Definition
metoclopramide, which *blocks the enteric GI presynaptic dopamine-D2 receptors. metoclopramide increases ACh activity (cholinomimetic), increases upper GI tone/mobility and also has anti-emetic effects via CNS activity
Term
what ADRs are associated with metoclopramide?
Definition
increased GI motility (possible diarrhea), and dopamine receptor antagonism in the CNS leading to extrapyramidal effects (like parkinson's): seizures, increased prolactin, galactorrhea, and menstrual irregularities
Term
what are the other prokinetic drugs used for tx of GERD?
Definition
*bethanechol which has muscarinic (M3) actions which increase LES pressure and GI motility and *erythromycin which is a motilin agonist that increases GI motility
Term
what acid suppressors are useful in treating GERD?
Definition
proton pump inhibitors are preferred (esp for more serious cases w/esophageal erosion), H2 blockers hasten healing w/excessive heartburn, and antacids/sulcrafate can provide some relief in milder conditions
Term
what kind of disease is IBS?
Definition
a nonorganic functional disturbance with an etiology that includes pyschosocial, altered motility (increased gastrocolonic response), and incresed GI sensory response (volume/distension)
Term
how is IBS treated?
Definition
when symptoms occur: increased dietary fiber, antidiarrheals, antispasmodics, avoidance of excacerbating foods, and adminstration of drugs that block serotonin receptor activity
Term
how do drugs that block serotonin receptor activity help with IBS?
Definition
GI 5-HT3 receptors activate visceral afferents, resulting in nausea/bloating/pain/inhibtion of L colonic motility. drugs such as *alosetron* are 5-HT3 receptor antagonists used to treat women when diarrhea is their main complaint via decreasing GI motility
Term
what ADRs are associated with alosetron?
Definition
severe constipation and life-threatening acute ischemic colitis - bad enough that drs have to enroll pts in a special progam to prescribe it
Term
what are the 2 kinds of inflammatory bowel disease?
Definition
ulcerative colitis and crohn's disease
Term
what drugs are used to treat inflammatory bowel disease?
Definition
5-aminosalicylic acid (5-ASA) drugs: sulfasalazine/balsalazide/olsalazine/mesalamine, antimicrobials (metronidazole, ciprofloxacin), corticosteroids for acute flares, immunosuppressives: azathioprine, mercaptopurine - anti-TNF drugs, and experimentally: methotrexate/cyclosporine
Term
how do the 5-aminosalicylic acid (5-ASA) drugs help with IBD?
Definition
*topical distribution in the GI, not systemic bc the colonic bacteria break the azo bond and release the ASA with sulfasalazine/balsalazide/olsalazine and with mesalamine, the acrylic coating dissolves at the ph 7 found in the terminal ileum/colon (ASACOL), ethylcellulose coated-time release throughout the GI (PENTASA), or mesalamine enema (ROWAWA and CANASA)
Term
what ADRs are associated with 5-aminosalicylic acid (5-ASA) drugs?
Definition
rash, fever, flu-like symptoms, GI disturbances/diarrhea, salicylate toxicity at higher doses, and sulfasalazine can form sulfapyridine which when absorbed can cause allergy/rash/hemolytic anemia/folic acid absorption interference
Term
what are the anti TNF drugs? what are they indicated for?
Definition
infliximab, adalimuma, and certolizumab are indicated for acute/chronic chron's disease (remission/maintenance) and act by preventing TNF binding to receptores. they are used in pts w/inadequate response to mesalamine/steroids
Term
what ADRs are associated with infliximab, adalimuma, and certolizumab?
Definition
infection, antibody development, infusion rx, and autoimmune rxs
Term
what is considered ulcerative proctitis/distal colitis? how is it generally treated?
Definition
< 40 cm - generally treated with mesalamine suppositories or steroids such as budesonide (formulated to release in the intestines)
Term
what is considered ulcerative colitis? how is it generally treated?
Definition
> 40 cm, oral mesalamine/sulfasalamine, steroids, mercaptopurine/azathioprine for steroid-dependent/cyclosporine-dependent remissions and antibx if acute infection present
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