peptic diseases pharmacology Flashcards
Pharmacological treatment of PU categories?
Agents affecting gastric secretion
Mucosal Protective Agents
Post secretoryagents
Agents affecting gastric secretion?
PPI
Anti H2 -histamines
Mucosal Protective Agents?
Prostaglandins
Post secretoryagents?
Anti-acids
receptors on parietal cells?
H2 histamin (Gi)
colicystokinin B (gastrin, Gq)
M3 (Ach, Gq)
E2 (PG, Gi)
PPI targets?
inhibitors of the gastric H+, K+-ATPase
covalent inhibition
PPI mechanism of action?
p/o prodrug blood entrocytes canaliculi (acid inviroment) activation H+, K+-ATPase covalent inhibition
PPI paradox?
lond lasting effect
short half life (0.5-2h)
How to prevent degradation of proton pump inhibitors by acid
enteric coated prodrug
PPI drug examples
omeprazole lansoprazole rabeprazole pantoprazole (prazole)
PPI side effects?
generaly safe
common side effects:
Diarrhea, headache, and abdominal pain
prolonged: subnormal B12 levels (intrinsic factor, PH)
Respiratory and Enteric Infections due to PH change
rebound hypersecretion of gastric acid upon discontinuation of therapy
histamine receptors characteristics?
H1 + H2 are peripherial
H1 s.muscle, endothel, brain (Gq)
H2 gastric mucosa, cardiac muscle, mast cells, brain (Gs)
both basolaterl in parietal cells
H2-receptor antagonists indications?
Gastric and duodenal ulcers
Uncomplicated GERD
Stress ulcers (prevent the occurrence)
H2-receptor antagonists examples?
cimetidine (1) > rantidine (4-10) > nizatidine (4-10) > famotidine (20-50)
most usable are rentidine anf famotidien
H2 receptor antagonists most common side effects?
Diarrhea headache fatigue myalgias constipation
H2-receptor antagonists IV administration side effects?
mental status change
cimitidine side affects?
inhibits binding of dihydrotestosterone to androgen receptors inhibits metabolism of estradiol increases serum prolactin levels genicomastia
PG Mechanism of action?
reducing histamine-stimulated cAMP production in parietal cells
bicarbonate secretion
enhance mucosal blood flow
PG ananlougs example?
misoprostol- synthetic analogue of PGE1
-prevention of NSAID-induced ulcers in high-risk patients
Mucosal Protective Agents examples?
Sucralfate
Bismuth chelate
Sucralfate Mechanism of action?
salt of sucrose complexed to sulfated aluminum hydroxide
polymerization (6 hrs) ⇒ Stick to ulcer craters
Bismuth chelate Mechanism of action?
stong affinity for mucosal glycoproteins, especially in the necrotic tissue of the ulcer craters ⇒
polymerization
Pink bismuth contraindication?
bismuth subsalicylate ⇒ subsalicylate like compounds (Asperin) cause Ray’s syndrome in fever acompanied diseases (as viral infections)
Anti-acids mechanism of action?
Neutralize HCl to form H2O + salt
Sodium bicarbonate → NaCl+ CO2
Calcium bicarbonate → CaCl2 + CO2 (slower
reaction with HCl)
Magnesium hydroxyde → MgCl2+ H20
Aluminium hydroxyde → AlCl3+ H20
hydroxydes can be given simultaniously
Imidiate but temporary relief 20-30 min
affect the absorption of other medications
by binding the drug
or
by increasing intragastric pH
→
should not be given within 2h before tetracyclines, fluoroquinolones, itraconazole, iron and others
Sodium bicarbonate Adverse effects?
Gastric distention
Belching
Metabolic alkalosis in patients with renal insufficiency
Exacerbate fluid retention in patients with heart failure, hypertension, and renal insufficiency
Calcium bicarbonate Adverse effects?
Belching
Metabolic alkalosis
Excessive doses of calcium (dairy) lead to hypercalcemia, renal insufficiency, and metabolic alkalosis (milk-alkali syndrome)
Aluminum hydroxide Adverse effects?
May cause constipation
Patients with renal insufficiency should not take these agents long-term (can aggregate)
Magnesium hydroxide Adverse effects?
May cause diarrhea
Patients with renal insufficiency should not take these agents long-term (can aggregate)
