GI meds Flashcards
What are the three cells in the stomach glands?
Mucous neck cells
Chief cells
Parietal cells
What do the three main cells secrete in the stomach?
Mucous neck cells- Mucin
Chief cells- Pepsinogen and gastric lipase
Parietal cells- HCl
What receptors do parietal cells contain?
Gastrin, Histamin, and Ach
Explain the events of acid secretion.
Ach/gastrin bind to parietal cells, causing increase in cytosolic Ca, stimulating protein kinases. This stimulates acid secretion from H/K ATPase
What is the function of carbonic anhydrase?
Converts H2CO3 into H+ from water
Forms H2O3 from water and CO2
What is one way to treat hyperacidity through inhibition of production? The med that can do this is?
Inhibiting formation of HCl through carbonic anhydrase inhibition (So H2CO3 hydrolysis is inhibited)
Acetazolamide
What drugs inhibit secretion of H+ ions into the lumen? How do these inhibit HCl?
Antimuscarinic, histamine blockers, and PPI
Inhibit H+ release prevents HCl from being formed
What is the definition of antacids? What is their MOA?
Weak bases that react with gastric hydrochloric acid to form salt and water.
Neutralization of acid. Causing reduction of intra gastric acidity
What is the ANC?
Acid neutralizing capacity. Number of milliquivalents of 1N HCL that brought to pH to 3.5 by a unit dose of antacid.
What drug category is baking soda and alka seltzer?
Antacid-Sodium bicarbonate
What drug category is tums and Os-cal?
Antacid- Calcium carbonate
What are the ADE’s for excessive calcium carbonate with Ca containing dairy products?
Hypercalcemia, renal insufficiency, and metabolic alkalosis (Milk alkali syndrome)
What is a benefit of the magnesium hydroxide or aluminum hydroxide compared to other antacids?
No gas is generated, so no belching
How are magnesium hydroxide or aluminum hydroxide normally administered?
Proprietary formulations
How should not take magnesium/aluminum hydroxide?
Patients with renal insufficiency because Mag and Al are excreted by kidneys
What are the general ADEs of antacids?
Rebound hyperacidity-Transient and mild
Milk-alkali syndrome
Drug specific toxicities
What are the drug specific toxicities for antacids?
Mg containing antacids-Laxatives
Al containing antacids-constipation
Al containing antacids-inhibit absorption of some drugs like digoxin and indomethacin
What are the MOAs of cytoprotective/mucosal protective agents
DO NOT interfere with HCL, but protect interior of stomach against acidity by establishing a pH gradient within the mucous layer. Also somehow helps repair injured epithelium through restitution
What are some example of cytoprotective agents?
Sucralfate, bismuth salts, and prostaglandins
What is sucralfates main use? Why?
Prevention of stress related bleeding because there are concerns that antacids, H2 blockers, and PPIs increase risk of nosocomial pneumonia
What is bismith salts used for?
Dyspepsia and acute diarrhea
What is the provided prostoglandin prototype?
Misoprostol
What are the side effects of bulk forming laxatives?
Minimal….
What is a beneficial part to bulk forming laxative?
May be beneficial to heart
What are stool surfactant agent (softeners) examples?
Docusate and glycerin suppository
What is the MOA of osmotic laxatives?
They are soluble but not absorbable compounds, so they increase stool liquidity by allowing more water to be in the GI tract
What are examples of osmotic laxatives?
Magnesium hydroxide, sorbitol, and lactulose
Polyethelene glycol
What does polyethylene glycol contain?
Inert, nonabsorbable, osmotically active sugar
What is a drug to drug concern with PEG?
Tartaric acid, some heart concerns I guess
What are the two different stimulant laxatives?
Anthraquinone and diphenylmethane derivatives
How do stimulant laxatives work?
Induce BMs by direct stimulation of enteric nervous system, and colonic electrolyte and fluid secretion
What are the chloride channel activators?
Lubiprostone, linaclotide
What is the MOA of lubiprostone?
Stimulates type 2 chloride channel in small intestine
What is lubiprostone/linaclotide used for?
IBS
Chronic constipation-Only linaclotide
What is the MOA of opioid receptor antagonists as a laxative?
Inhibit u-opiod receptors… IDK
What are the listed opioid receptor antagonists?
Alvimopan and naloxigel
Do the opioid receptor antagonists cross the BBB?
No
What are some ADEs of alvimopan?
CV toxicity, only for short tem use
What is naloxigel contraindicated in?
Suspected GI obstruction
Patients on strong CYP 3A4 inhibitors because they may worsen opioid withdrawal
Also patients on CYP3A4 INDUCERS
Strong CYP3A4 inhibitors listed were clarithromycin and ketoconazole, diltiazem, and verapamil
What is naloxigels ADEs?
May cause opiod withdrawal in fetus
Does Loperamide cross the BBB?
No
What are the opioid antidiarrheal agents?
Loperamide and diphenoxylate
What are the three drug classes that can inhibit secretion of H+ into the lumen of the stomach?
Antimuscarinic, histamine blockers, PPI
What are the antimuscarinic drugs mentioned?
Atropine, scopolamine
What are the ADEs of atropine?
Dry mouth, constipation
What is a better antimuscarinic drug to use than atropine for acid reduction?
M1 selective drugs to avoid atropine like side effects
Atropine is an M2 receptor antagonist
What are the H2 blockers? aka histamine blockers
Cimetidine, ranitadine, famotadine, nizatadine
How do H2 blockers reduce gastric acid secretion?
Blocks binding histamine from binding to parietal cell H2 receptor
Direct stimulation of parietal cell by gastrin or Ach and causes the cell to have a DIMINISED EFFECT on acid secretion in presence of H2 receptor blockade
What are H2 antagonists specifically effective at inhibiting?
Nocturnal acid secretion
What are the uses of H2 blockers?
GERD, PUD, nonucler dyspepsia, prevention of bleeding from stress related gastritis
What are drug interactions with cimetadine?
Binds to CYP450
Ranitadine does as well, but to a lesser extent
What are the common PPIs?
Omeprazole, esomeprazole, lansoprazole, dexlansoprazole, rabeprazole, pantoprazolw
What is PPIs MOA?
Gets into the parietal cells, accumulates in parietal cells, covalently bind H/K ATPase
This is IRREVERSIBLE
Inhibits this proton pump… which is a H pump
PPI are administered as a ____
Prodrug
What is the treatment for Zollinger Ellison syndrome?
PPIs
What are the ADEs of PPIs?
Omeprazole and esomeprazole inhibit CYP2C19
This CYP also is used for plavix
Subnormal B12 levels
