GI drugs Flashcards by Emily Harrison

Antibiotics given to fight H. pylori

Amoxicillin-preferre
Carithromycin- increasing resistance
Metronidazole-alternative for allergy
Tetracycline-for quadruple therapy

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MOA of bismuth subsalicylate

antibacterial activity against H. pylori
binds E. coli enterotoxins
forms a barrier
anti-secretory and anti-inflammatory activities of salicylate

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Therapeutic use of bismuth subsalicylate

PUD, diarrhea, nausea and cramping

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Adverse effects of bismuth subsalicylate

harmless black discoloration of stool and tongue, salicylism at high doses (tinnitus) Reye’s syndrome, use with caution in children

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Antacid prototypes

magnesium hydroxide and aluminum hydroxide

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MOA of antacids

raise stomach pH

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Pharmacokinetics of antacids

1-2 hrs

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Differences between Mg and Al hydroxide

Mg2+ -diarrhea due to peristaltic stimulation, Al smooth muscle relaxation

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Therapeutic use of antacids

largely replaced by more effective, mild symptoms

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Drug interactions of antacids

can interfere with absorption of other drugs

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Prototype histamine receptor antagonists

cimetidine

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MOA of histamine receptor antagonists

blocks acid secretion from parietal cells stimulated by histamine, highly selective for H2

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Therapeutic use of H2R antagonists

supress total acid secretion by 70%, most effective in suppressing nocturnal acid secretion
Slower onset and longer duration than antacids, prophylactic
Tolerance can develop

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Adverse reactions of H2R antagonists

edocrine effects- loss of libido, impotence and gynocomastia
CNS effects- rare, in elderly with decreased liver/kidney function
Pneumonia-increased bacterial colonization

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Drug interactions with H2R antagonists

cimetidine inhibits multiple cyp isoforms

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Prototype PPI

omeprazole

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MOA of PPIs

irreversibly inhibits H+, K+ ATPase that are active

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Pharmacokinetics of PPI

30 min before meals, reduces acid secretion by 95%, effects persist for 2-3 days
Enteric coated to get to small intestine

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Metabolism of PPIs

hepatic metabolism by CYPs, asian variant correlates with slow metabolism, dose reduction in patients with hepatic disease

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Therapeutic uses of PPI

PUD, GERD, Zollinger-Ellison syndrome, NSAIDs associated ulcers

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Adverse reactions of PPIs

nausea, abdominal pain, constipation/diarrhea, flatulence
pneumonia
fractures due to decreased Ca+ absorption
rebound hypersecretion upon discontinuation

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Drug interactions with PPIs

warfarin, diazepam, cyclosporine

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Mucosal protective agent prototype

sucralfate

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MOA of sucralfate

forms a gel at low pH, binds necrotic tissue forming a barrier to acid and pepsin

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Therapeutic use of sucralfate

duodenal and stress ulcers, stomach pH not increased, does not increase pneumonia risk

Adverse reactions of sucralfate

constipation, reduced absorption of other drugs

PGE1 analog prototype

misoprostol

MOA of misoprostol

reduces acid secretion from parietal cells by simulating PGs

Therapeutic uses of misoprostol

NSAIDS patients, contraindicated in pregnancy (can induce abortions)

Adverse effects of misoprostol

dose dependent diarrhea and abdominal pain

Bulk forming laxative prototype

psyllium

MOA of psyllium

non-digestible agents that swell with water to for a viscous solution that softens and increases stool volume, increasing peristalsis

Adverse effects of psyllium

must be taken with water to prevent impaction

Prototype surfactant laxative

docusate sodium

MOA of docusate sodium

lower surface tension, allow penetration of water

Stimulant laxative prototype

bisacodyl

MOA of bisacodyl

stimulates by irritant effects GI motility and increase water and electrolytes in lumen

Therapeutic use of bisacodyl

widely used, abused opiod induced constipation slow intestinal transit constipation

Adverse effects of bisacodyl

proctitis with long term use

Prototype osmotic laxative

magnesium hydroxide

MOA of magnesium hydroxide

poorly absorbed salts or sugars whose osmotic action draws water into the intestinal lumen. causes swelling of stool and stretching of GI wall

Therapeutic uses of magnesum hydroxide

low dose- group II effect for mild to moderate constipation | high dose-group I effect fluid evacuation of bowel

Adverse effects of MgOH

can cause dehydration and electrolyte imbalance. Systemic absorption of Mg can cause toxicity

Antidiarrheal agents

loperamide, diphenoxylate

MOA of loperamide and diphenoxylate

agonists at myenteric opiate receptors reduces secretory activity (delta) and GI motility (mu) Loperimide is 50x more potent than morphine

Pharmacokinetics of opiod antidiarrheal agents

well absorbed orally Loperamide- poor pentration across the BBB, available OTC Diphenoxylate- BBB permeable, schedule V, sometimes contain atropine

Targets for antiemesis

Serotonin acting at 5-HT3 receptors Dopamine acting at D2 receptors Substance P/neurokinin 1 (NK1) receptor Histamine and muscarinic R in vesibular apparatus glucocorticoid, cannabinoid, GABA and opiod receptors

opiod antagonist for opiod induced constipation

methylnaltrexone

5-HT3 receptor antagonist prototype

ondansetron

Pharmacokinetics of ondensetron

IV, but prophylactic oral, long duration, cleared by CYPs

Thereapeutic use of 5-HT3 R antagonists

CINV and radiation pregnancy and postoperative not effective aginst motion sickness or delayed CINV nausea

Adverse effects of 5-HT3R antagonists

well-tolerated, constipation/diarrhea, headache

Prototype NK1 receptor antagonists

aprepitant

Pharmacokinetics of aprepitant

metabolized by CYP3A4, induces CYP2D6

Therapeutic uses of aprepitant

delayed nausea, improves efficacy of other agents in CINV

Regimen of choice for CINV

aprepitant, dexamethasone, 5-HT3 antagonist

Treatment for IBS-C

dietary fiber (psyllium) and osmotic laxatives

Treatment of IBS-D

loperamide

5-Ht3 R antagonists for IBS-D

alsetron

MOA of alsetron

decreases GI motility and secretions and inhibits unpleasant visceral sensations

Therapeutic use of alsetron

IBS-D in FEMALE, for severe symptoms lasting longer than 6 months, refractory to all other medications

Adverse effects of alsetron

severe constipation, life threatening ischemic colitis

Mesalamine (5-ASA) based therapy prototype

sulfasalazine

MOA of sulfasalazine

prodrug N=N bond cleaved by intestinal flora to release 5-ASA, which is immune suppressive

Adverse effects of sulfasalazine

due to metabolite, GI, headaches, arthralgia, myalgia, myelosuppresion

Anti-TNF based therapy for IBD

inflizimab

Side effects of inflizimab

injection site and infusion reactions, neutropenia, infection (TB), heart failure, malignancy (lymphomas), pulmonary disease, demyelinating disease, cutaneous reactions, allergic reactions.

GI drugs Flashcards

(67 cards)