Pharm - Antacids & Anti-Ulcer Flashcards
What are the two main types of antacids?
- low-systemic agents
- high-systemic agents
(plus supplemental agent: simethicone)
what are the 3 classes of low-systemic agents?
- aluminum salts (aluminum hydroxide)
- calcium salts (calcium carbonate)
- magnesium salts (magnesium hydroxide/carbonate/trisilicate)
what is the one class of high-systemic agents?
sodium bicarbonate
why is sodium bicarb not prescribed for anacid treatment anymore?
it is highly absorbed, leading to hypernatremia -> bad
what bind to H+ ions in the gastric lumen, that have already been released by parietal cells?
antacids
- they do NOT decrease acid production or secretion!!
- result in generation of common by-products (water, CO2, chloride salts)
what are the onset, DOA, and acid neutralizing capacity (ANC) of calcium and magnesium salts?
onset: rapid
DOA: long
ANC: Ca=very good, Mg=good
what supplemental compound decreases surface tension, aiding the expulsion of gas?
simethicone
- does NOT prevent gas, just makes it easier to expell
what are the two main side effects of aluminum salts?
constipation, hypophosphatemia
what are the two main side effects of magnesuim salts?
diarrhea, hypermagnesemia
what are the three main side effects of calcium salts?
constipation, hypercalcemia, hypophosphatemia
what are the three main side efffects of sodium bicarb?
- gas/flatulence, hypernatremia, metabolic alkalosis -> now is used more to treat pts with pH imbalance (acidotic)
what are the two antacid combinations used to balance side effects?
- Mg + Ca
- Mg + Al
NOTE: if pt already has loose stool, don’t give Mg. same goes for constipation
what is the timing for antacid drugs?
take all 1-2 hours BEFORE other medications, OR 2-4 hours AFTER other meds
what are the 5 categories of anti-ulcer drugs?
- H2 blockers
- Proton pump inhibitors
- Surface acting agents
- PGE1 analogs
- Bismuth compounds
- cimetidine
- ranitidine
- famotidine
- nizatidine
Histamine type-2 blockers
what is the MOA of H2 blockers?
they block the H2 receptor on the baso-lateral membrane of the parietal cells
- relatively prompt relief of GERD symptoms
- ulcer healing occurs 4-8 weeks, but NOT if caused by H.pylori
(gastrin binds CCK2r on ECL cell -> Hist released, binds H2r on parietal cell)
what are the adverse effects of H2 receptor blockers?
nausea, diarrhea, constipation, sometimes headache
RARE: cimetidine decreases testosterone binding to androgen receptor -> gynecomastia in men, galactorrhea in women
what two drugs are important examples of CYP450 inhibitors?
cimetidine and omeprazole
NOTE: ranitidine only has about 10% inhibition compared to cimetidine
what H2 blocker is contraindicated in pregnancy? what can be used instead?
ranitidine
- use famotidine instead
- omeprazole (po)
- esomeprazole (po/iv*)
- lansoprazole (po)
- dexlansoprazole (po)
- pantoprazole (po/iv*)
- rabeprazole (po)
proton pump inhibitors (PPI’s)
what is the MOA of PPI’s?
they bind sulfhydryl groups of H/K-ATPase on the lumen of parietal cells, inhibiting gastric acid secretion into the mucous layer
- not as fast acting as H2 blockers, full symptom effects seen in a few-several days
- ulcerations healed in 4-8 weeks, but NOT if caused by H.pylori*
what are the adverse effects of PPI’s?
diarrhea, dyspepsia, nausea, headaches, generalized myalgia
- CDAD (C.diff assoc diarrhea) an additional concern, stop taking PPI immediately if pt gets foul-smelling watery diarrhea!
what PPI is contraindicated in pregnancy? what can be used instead?
lansoprazole, also try to avoid omeprazole
- use pantoprazole instead
sucralfate
sulfated polysaccharide
what is the MOA of sucralfate?
bandaid!
- interacts with stomach acid, creating a viscous, sticky polymer which adheres to epithelial cells around ulcer’s crater
- forms protective barrier so more acid can’t irritate the ulcer further
NOTE: viscous blob will NOT adhere to normal epithelial tissue, so tx should be stopped once ulcer is healed
what might sucralfate also stimulate?
local prostaglandin release, mucous production, and epidermal growth factor
- does not affect pH
when is sucralfate indicated?
duodenal ulcers, but also off label for
- aphthous ulcers (canker sores)
- mucositis
- radiation proctitis/ulcers
what is the main adverse effect of sucralfate?
constipation -> added to Al(OH)3
what is a relative contraindication of sucralfate?
severe renal failure (d/t aluminum)
NOTE: possible drug-drug interactions, so should be taken 2 hours after other meds like antacids
what is the dosing regimen for sucralfate?
4 times daily
- take 2 hours after other medications, LOTs of drug interactions
what is the MOA of misoprostol?
- prostaglandin E1 analog, reduces gastric acid release from parietal cell negative effect
- provides CYTOprotection (brand name is CYTOtec) by increasing mucosal defenses by making bicarb, mucous and increased blood flow positive effect
what is the indication for misoprostol?
prevention of NSAID induced gastric ulceration in high risk patients
- cervical ripening
- post-partum hemorrhage (high dose given rectally)
what are the two main contraindications of misoprostol?
- pregnancy because it induces labor!
- IBD
what are the adverse effects of misoprostol?
diarrhea, headache, dizziness
what is the MOA of Bismuth compounds?
(Pepto-Bismol!) most well known for its antimicrobial properties, prevents microbial attachment to mucosa, possible inactivation of enterotoxins, disruption of bacterial wall
- Rx: given in combination pack to treat H.pylori
- OTC: used alone for reflux, bloating, gas
what are the adverse effects of Bismuth compounds?
constipation, black/dark REGULARLY-formed stools
NOTE: if pt has black TARRY stool -> think GI bleed!
what is the dosing regiment for Bismuth compounds?
take 2 hours after other medications, LOTs of drug interactions
what are the absolute contraindications of Bismuth compounds?
GI bleeding, salicylate hypersensitivity
what is the preferred treatment of H. pylori?
- *COMBINATION THERAPY IS A MUST**
- at least 2 antibiotics and an acid reducer (PPI or H2 blocker) for 10-14 days**
what can lead to false negatives on urease breath tests?
consuming Bismuth compounds within 4 weeks prior to performing test
what is the triple therapy for H. pylori?
this is the GO-TO tx
- PPI
- clarithromycin
- either amoxicillin OR metronidazole (if allergic to amox)
*all 2x a day, for 14 days!
what is the quadruple therapy for H. pylori?
- PPI**
- metronidazole
- tetracycline
- Bismuth subsalicylate
*PPI 2x a day, all others 4x a day for 10-14 days!
what is the H. pylori treatment if pt has PCN allergy?
use metronidazole, NO amoxicillin
what is the treatment for H. pylori with metronidazole resistance?
substitute tetracycline, consider quadruple therapy
NOTE: some communities have H. pylori resistance, can default to quad therapy
**what should you consider in pregnant patient with PUD
if they don’t have H. pylori, consider short course of antacids or sucralfate
- if moderate symptoms, consider ranitidine (H2 blocker)
- if severe symptoms, consider lansoprazole (PPI)
what should you consider if NSAID-at risk for pt with PUD?
- if NSAID not required, consider acetaminophen and /C NSAID
- if NSAID required, consider COX-2 NSAID and/or consider PPI or misoprostol
