GI Meds Flashcards
Proton Pump Inhibitors
Omeprazole
Administration of omeprazole
administered as inactive acid-liable pro-drugs that have an enteric coating to protect against rapid destruction in the stomach. Dissolved and absorbed in the intestines.
Mechanism of Omeprazole
Absorbed in intestine where it is acid activated and blocks H-K-ATPase irreversibly by forming a covalent bond with SH-groups of H-K_ATPase. ATLEAST 18 HOURS ARE REQUIRED FOR FORMATION OF A NEW ATPASE
How often is Omeprazole given?
Once daily, twice is severe GERD, should be given 30 min before meal for peak plasma levels.
By what percent does food decrease the bioavailability of Omeprazole?
50%
Why does ir take 3-4 days of daily medication for full acid inhibition?
Not all H-pumps are inactivated with the first dose
Uses of omeprazole
gastric ulcers, alone or in combo with H. pylori; also used in GERD
DRUG OF CHOICE WITH ZOLLINGER ELLISON SYNDROME
T/F: Proton pump inhibitors are superior to H2 receptor antagonists and to mucosal protectants in the healing of NSAID Peptic Ulcers
True
WHy should you avoid omeprazole and plavix?
Omeprazole is a moderate CYP2C19 inhibitor, that reduces the pharmacological activity of plavix(clopidogrel). Avoid using concomitantly or 12 hrs apart.
Histamine H2-receptor antagonist
Cimetidine
Main role of cimetidine
Inhibits fasting secretion of gastric acid with a smaller effect on food stimulated gastric acid secretion. Competetive inhibitor at the parietal cell H2-receptor. ALSO BLUNTS RESPONSES TO GASTRIN AND ACH
Uses of cimetidine
gastric ulcers, GERD, and heartburn
How safe is cimetidine?
Very safe its is available over the counter
Drug interactions of cimetidine
interferes with metabolism of other drugs due to inhibition of cytochrome p450
Mucosal Protective agents
Misoprostol, Sucralfate, Bismuth subsalicylate
Misoprostol
A stable analog of PGE that bings to the PG receptro and causes a modest inhibition of acid secretion. Cytoprotective.
PROMOTES SECRETION OF MUCUS AND BICARB
Uses of misoprostol
prevention of gastric damage due to chronic use of NSAIDs
Side effects of Misoprostol
diarrhea and abdominal cramps. DO NOT USE IF PREGNANT- CAN CAUSE ABORTION DUE TO UTERINE CONTRACTION
Sucralfate
Complex of Al(OH)3 and sulfated sucrose. Cytoprotective. Coats gastric mucosa and stimulates PGE production.
Drug interactions of sucralfate
reduces absorbtion of digoxin, phenytoin
Bismuth Subsalicylate
Cytoprotective, may inhibit pepcin activity and increase mucus , prostaglandin and bicarb secretion.
Uses of Bismuth Subsalicylate
mild diarrhea, been used in clinical trails for eradication of h. pylori. may also have some antibacterial effect against H. pylori (used to eradicate h. pylori)
People dont like it because of bad taste
Adverse effects of bismuth:
patients sensitive to asprin may show sensitivty to salicylate
Drugs that stimulate gi motility
Metoclopramide and Erythromycin
Metoclopramide
A dopamine D2 receptor agonist that releases Ach from cholinergic neurons in myenteric plexus, enhancing tone and motility in esophagus and stomach stimulating gastric emptying with out stimulating acid secretion
only works on upper gi
Uses of metoclopramide
GERD, heartburn, disorders of gastric emptying and intractable hiccup
Adverse effects of metoclopramide
extrapyramidal side efects such as parkinsonism, contraindicated in people with seizure disorders and in mechanical obstruction of GI tract
Erythromycin
Stimulates motilin receptors (motilin is a polypeptide hormone that mediates intestinal smooth muscle contraction)
Uses of erythromycin
used in diabetic gastrophoresis and in upper gi hemorrhages to promote gastric emptying before endoscopy
Anti emetics
5-HT3 receptor antagonist: ondansetron
odansetron
prevents peripheral and central stimulation of VC by blocking 5-ht3 receptors in stomach, STN and CTZ.
has a long half life, given once or twice daily
interesting effect of odansetron
increases qt interval but not usaully clinically significant
uses of odansetron
effective against chemotherapy and pregnancy induced nausea and vomiting
Drugs used in IBD
5-aminosalicylic acid, sulfasalazine (need to supress the inflammatory and immune responses)
Glucocorticoids
prednisone and prednisolone (Budesonide is a synthetic analog of prednisone that releases the drug into the distal ileum and colon where it is absorbed)
Uses of glucocorticoids
treat moderate to severe FLARES of IBD
Purine analogs
Azathioprine and 6- mercaptopurine (immunosuppressants)
Adverse effects of purine analogs
nausea vomiting, bone marrow depression and hepatic toxicity
Methotrexate
may interfere with inflammatory action of IL 1, increase release of adenosine, stimulates the death of activated t cells
Uses of methotrexate
induce and maintain remission of crohns
Adverse effects at higher doses with methotrexate
bone marrow depression, megablastic anemia, and alopecia
How do you avoid adverse effects of methotrexate
supplement with folate
Inflixamab
monoclonal antibody to TNF alpha, inhibits it from binding to receptor.
Uses and adverse effects of Inflixamab
uses: UC CD
ae: infection due to suppression of inflammatory response
