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Flashcards in Upper GI pharmacology Deck (24)
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Prostaglandins have what effects on the epithelial cells vs. parietal cells of the stomach?

• Epithelial - increased mucus and bicarbonate secrtion
○ Cytoprotective
• Parietal cell
○ Inhibit cAMP which in turn down regulates the amount of protein kinases phosph and activating the H+/K ATPase
○ End result is less H+ secretion
• Thus, NSAIDs, which inhibit PG synthesis will lead to increased overall H+ secretion and decreased mucus and bicarbonate secretion to balance out the acidity


What role do antibiotics play in the treatment of upper GI disease?

• Critical role in H pylori infection eradication
• H pylori is associated with 85% of duodenal ulcers
• Antibiotic therapy to reduce rate of recurrence of gastric ulcers with 50-80% success and duodenal ulcers with 90-95% success
• Used as triple, quadruple or sequential therapy for H pylori treatment


What is "quadruple therapy"

• Add bismuth subsalicylte to the antibiotics
• Different antibiotic combo
○ Metronidazole - tetracycline
• Also the PPI is in there OR H2 antagonist


What is "triple therapy"

• In the context of H pylori treatment
• Clarithromycin-amoxicillin
• OR metronidazole (instead of amoxicillin)
○ The acute ulceration problem is treated by acid suppression


What is sequential therapy for PUD?

• In the context of H pylori infection, which is pretty much the causitive agent for duodenal ulcers
• Amoxicillin + PPI
○ 5 days
• Clarithromycin - Tinidazole
• + PPI for 5 days
• Quadruple and sequential have greater eradication rates than triple by 12% or so


What are the two bolded PPIs?

• Lansoprazole and omeprazole
• Remembe the prazoles


What are the pharmacodynamic properties of PPIs that are important?

• Prodrugs - diffuse into parietal cell before being activated and trapped in the acidic secretory cannniculi
• Irreversible inactivation of the enzyme
• 18 hours is the time to produce new enzyme thus good efficacy throughout the day (though plasma 1/2 life is way less than that)
• Takes 2-5 days to reach maximum intracellular concentration
• Optimum inhibtion is 80%
• Efficacy of all the options in this class are the same at comparable doses


When should PPIs be taken?

• 1 hour before meals on an empty stomach
• Peak plasma concentration should occur with maximal proton pump secretion


How are PPI's metabolised/eliminated?

• Rapid first pass metabolism via CYP450 enzymes
○ 2C19 and 3A4
• With severe liver disease watch out
• Do problems with normal dosing with renal failure patients


What are the 5 clinical scenarios that PPI use is indicated in?

• Peptic ulcer disease
• NSAID-induced ulcers
• Prevention of stress gastritis
• Zollinger-Ellison syndrome


What are the adverse effects of PPIs to be aware of?

• Drug-drug interactions are the main ones
○ CYP450 interaction and potential inhibition of other liver metabolized drugs
○ There is competition, not true induction or inhibition
• In particular, clopidogrel interaction and it won't be made into active anti-platelet form


What are the bolded H2 receptor antagonists?

• Ranitidine
• Cimetidine
• Famotidine
• Nizatidine
○ All are OTC drugs for acute gastritis


What are the pharmacodynamic properties for the H2 receptor antagonists?

• Mechanism - reversible, competitive block at parietal cell H2 receptors on basolateral membrane
• Less efficacious than PPIs but still get 24 hour secretion down by 70%
• BETTER at blocking nocturnal secretion which is histamine mediated
• This is used for treatment of and healing of ulcers (supression of nocturnal release is key to healing)


What are the pharmacokinetic properties of H2 receptor blockers to know?

• Rapidly absorbed from GI tract
• Some enhancement with food and a small decrease if given with antacids
• Less protein binding than PPIs
• Some hepatic metabolism, but not enough to change dose in liver disease
• Major excretion is renal
○ 1/2 life of 1-4 hours depending on dose
• Must reduce dose in renal impairment


What is the elimination profile of the H2 receptor blockers?

• Some hepatic metabolism, but not enough to change dose in liver disease
• Major excretion is renal
○ 1/2 life of 1-4 hours depending on dose
• Must reduce dose in renal impairment


What are the clinical uses for H2 receptor blockers?

○ Though PPIs are preferred in severe erosive esophagitis
• Peptic ulcer disease
○ More for the nocturnal suppression and healing of ulcers
○ PPIs are mainline
• Stress-related gastritis
○ Reduced bleeding when given IV


What are the adverse effects seen in H2 receptor antagonist use?

• Generally well tolerated
• Some dizziness, diarrhea, constipation, headache
• Rare
○ CNS dysfunction - mental status changes, Slurred speech, confusion
§ Cimetidine in the elderly with renal impairment and ICU patients
○ Endocrine effects - cimetidine
§ Gynecomastia, galactorrhea, decreased spearm count
○ Blood dyscrasias - cimetidne
○ Reversible liver toxicity with all H2 receptor blockers


What are the drug interactions to be aware of in H2 receptor blocker use?

• Cimetidine inhibits cytochrome P450 oxidative matabolism
○ CYP1A2, 2C9, 2D6, 3A4
• Increase effects and toxicity of other agents
○ Theophylline, warfarin, phenytoin, carbamazepine, ketoconazole, itraconazole, benzos
• Mess with ketoconazole absorption by causing an increase in gastric pH
○ antifungal


What is sucralfate?

• Mucosal protective agent
• Essentially coats the necrotic surface of an ulcer and prevents futher damage
• Sulfated disaccharide aluminum salt
• Prevents pepsin hydrolyzation of mucosal proteins
• Have to give pretty frequently, 2-4 times a day
• Constipation is really the only side effect here


What is misoprostol?

• Prostaglandin PGE1 analog
• Inhibit cAMP, decreasing overall H+ secretion
• Stimulation of bicarb secretion
• Stimulation of mucus secretion
• Rapid oral admin (30 min)
• Also 30min 1/2 life, so 3-4/day dosing
• Major indication for use is NSAID-induced GI ulceration
• Diarrhea and uterine stimulation are side effects
○ Thus can't use in pregnancy


What are the primary neutralizing ingredients in antacid medicaitons?

• Calcium
○ Don't use for chronic use, but safe for symptomatic relief
○ Can use as Ca supplement
○ Renal calculi and constipation and hypercalcemia possible with chronic use
• Aluminum
○ Either hydroxide, carbonate or phosphate
○ Widely used
○ Binds phosphate in gut, so used in chronic renal failure
○ Chronic use may lead to CNS toxicity by way of encephalopathy
• Magnesium
• Sodium bicarbonate
○ Potent, effective
○ Systemic effects - Na overload and alkalosis
○ Avoid in - pregnancy, CHF, hypertension, edema, renal failure


Can you use antimuscarinics for upper GI problems?

• Yes, but they aren't great, and they have nasty side effects within the doses needed for upper GI relief
• Clinidium
• Glycopyrrolate
• propantheline


What are the 5 bolded promotility drugs?

• Erythromycin
○ Agonist at excitatory neural and smooth muscle motilin receptors
• Cisapride
○ Excitatory agonist at neural 5-HT4 receptors (ENS, cholinergic)
• Metoclopramide
○ Antagonist and inhibitory stimulation of presynaptic dopamine receptors
○ Inhibit ach release indirectly
• Neostigmine
○ Inhibits breakdown of ach by inhibiting ache
○ Thus, overall stimulation of motility
• Bethanechol
○ Direct excitatory agonist at M3 smooth muscle receptors
○ Pro-motility


Does direct M3 activation result in increased, coordinated peristalsis?

• Nope. It's more like overall contaction and motility, but not propulsive
• Tend to increase gastric and pancreatic secretions
• The better way to go is neuronal stimulation or ach release stimulation