peptic ulcers Flashcards
definition
erosion of the gastric/ duodenal mucosa up to lamina muscularis mucosae
classification of anti ulcer drugs
⦁ Antacids.
drugs suppressing secretion
⦁ Proton pump inhibitors (PPI).
⦁ H2 –histamine receptor blockers.
⦁ Antimuscarinic agents.
Mucosal protective agents.
drugs for the eradication of H.pylori
⦁ Antimicrobial agents for eradication of Helicobacter pylori.
classification of antacids
absorbable antacids
non absorbable
antacids (most common)
combined
⦁ Absorbable antacids
Sodium bicarbonate –pulv (can produce transient metabolic alkalosis; therefore, not recommended for long-term use).
° Calcium carbonate –tab (reacts with HCl to form CO2 and CaCl2; commonly used).
⦁ Non-absorbable antacids
Magnesium hydroxide –pulv.
° Aluminum hydroxide–pulv.
⦁ Combined preparations
Almagel (Muthesa) –susp. 170ml
° Maalox –tab; susp.
° Talcid –tab.
what are antacids
weak bases that react with gastric acid to form water and a salt,
diminishing gastric acidity.
take 1-3 hrs b4 meal and before bed
affect of antacids on pepsin
reduces it’s effect by increasing ph above 4 rendering it inactive
indication for aluminium and magnesium (non abs)
symptomatic relief of peptic ulcer disease and GERD.
why are absorbable antacids rarely used
increased ADR e.g.
kidney stones
altered bone mineralization
alkaline milk syndrome ( nausea vom diarrheoa)
benefits of combined antacids
al- prolonged effect
mg- fast onset
adr’s
⦁ Magnesium hydroxide: Diarrhea.
⦁ Aluminum hydroxide: constipation,
H2 RECEPTOR ANTAGONISTS
act selectively on H2 receptors in the stomach, blood vessels, and other.
competitive antagonists of histamine
fully reversible.
completely inhibit gastric acid secretion induced by histamine or gastrin.
H2 antagonist classification
FIRST GEN
⦁ Cimetedine –tab. 200 mg.
SECOND GEN
⦁ Ranitidine (Zantac) –tab. 150mg; 300mg.
THIRD GEN
⦁ Famotidine (Qamatel) –tab. 20mg; 40mg.
⦁ Nizatidine –tab.
how are H2 antagonis
phk ADME
ADMIN h2 antag
oral
IV less common
DISTRO: h2 antag
- breat milk
- cross placenta
Met:
liver
EXC: h2 blockers
urine
effects of cimetidine CYP450
cimetidine inhibits CYP450
increases serum lvl of
- theophyline
- diazepam
- warfarin
diff betw/ 1st gen cimetidine and 2nd gen ranitidine
ranitidine is longer acting
ranitidine is more potent
ranitidine doesn’t affect other drugs unlike cimetidine
compare famotidine to ranitidine
3 to 20 times more potent than ranitidine.
ADR of H2 antag
endocrine: gynecomastia reduced sperm count (CIMETIDINE, again)
CNS disturbed in elderly w/ iv admin
⦁ Inhibition of hematopoiesis.
drug interxns of H2 antag
cimetidine and ranitidine increases metabolistm
cimetidine increases drug conc of
- theophylline
- diazepam
- warfarin
ketoconizole rnneds acidity for absoprtion so has reduced absorption if taken w/ theses
PROTON PUMP INHIBITORS (PPIs)
⦁ Omeprazole (Sopral) –caps. 20mg.
⦁ Esomeprazole (Nexium) –tab. 20mg.
⦁ Rabeprazole (Pariet) –tab. 20mg.
PPI phD
prodrugs with an acid-resistant enteric coating
coating is removed in the alkaline duodenum
absorbed and transported to the parietal cell canaliculu
converted to the active form reacts with the H+/K+-ATPase, forming a stable covalent bond.
inhibit gastric acid secretion by more than 90 percent.
indications for ppi
5
⦁ Treating erosive esophagitis, GERD
⦁ Active duodenal ulcer;
⦁ Long-term treatment of Zollinger-Ellison syndrome);
⦁ PPIs reduce the risk of bleeding by aspirin and other NSAIDs.
⦁ PPIs used with antimicrobial regimens to eradicate H. pylori.
ppi phK
ADMIN: PPI
oral
DISTRO: ppi
MET: ppi
liver
EXC: ppi
urine
feces
ADR
⦁ Decreased vitamin B12 and calcium absorption due to suppressed gastric acid secretion.
⦁ Hypochlorhydria and risk of enteric infections.
⦁ The incidence of gastric carcinoid tumors increased
drug interactions of omeprazole d/2 CYP450 inhibition
inhibits metabolism of
- cyclosporine
- diazepam
- phenytoin
- warfarin
potentiating their adrs risk
mucosal protective agents
enhance mucosal protection mechanisms, preventing mucosal injury,
healing existing ulcers.
classification
Sucralfate (aluminium salt of sulfated sucrose) –tab. 500 mg:
Colloidal Bismuth Subcitrate(tab. 120 mg):
sucralfate MOA
polymerizes in acidic conditions
forms a protecting gel over ulcer
stimulates
- PGE2
- bicarbonate
sucralfate adr
constipation
sucralfate drug interxn
inhibits absoprtion of other drugs
Colloidal Bismuth MOA
binds glycoproteins and amino acids at ulcer base forming a coating.
stim PGE2 and bicarbonate
what effect does bismuth have that sucralfate doesn’t
bismuth has anti H.pylori effect
colloidal bismuth ADR
METAL TASTE
BLACK STOOLS
encephalopathy
ANTIMICROBIAL AGENTS FOR ERADICATION OF H.PYLORI:
Classification:M CAT 500
⦁ Metronidazole (Flagyl) –tab. 500mg.
⦁ Clarithromycin (Klacid) –tab. 500 mg.
⦁ Amoxicillin (Amopen) –caps. 1 g.
⦁ Tetracycline (Tetracycline) –caps. 500 mg.
describe the triple therapy for H.pylori eradication
1) PPI (omeprazole)2x/d
2) clarithromycin 500mg 2x/day
if resistant use
- metronidazole 500mg 2x/day
3) amoxicillin 1000mg2x/d or metronidazole if not used in step 2
how long should the rx last for
10 days/ 14 days
considerations in pregnancy
ppi cross placental barrier and are found in breast milk
replace w/ H2 blocker
bismuth salts are CI in pregnancy
ulcer rin liver failure
ppi has liver met
half the daily dose
cimetidine inhibits cyp450 so special care in liver failure as it worse
ulcer in kidney failure
h2 blockers excreted by kidneys at same rate as creatinine
reduce dose
