Week 5 - Acid-Controlling Drugs Flashcards
what 3 types of receptors trigger stomach acid production
- gastrin
- ACh
- histamine
what is the function of the proton pump
- pumps H+ from the parietal cell into the stomach lumen
- the H+ then combined with Cl to create stomach acid
describe the carbonic anahydrase rxn
- CO2 is combined with H2O to create carbonic acid
- carbonic acid is broken down into H+ and HCO3- (bicarb) by carbonic anahydrase
- the H+ gets transported into the cell via the proton pump
- the bicarb gets shifted out of the cell
what is the alkaline tide
- an efflux of bicarb into the blood after acid secretion in the stomach
list the 3 types of acid-controlling drug
- antacids
- H2 antagonists
- proton pump inhibitors
what is the primary function of antacids
- neutralize stomach acids
what is the secondary function of antacids
- promote gastric mucosal defense mechanisms
list 3 ways that antacids promote gastric mucosal defense mechanisms
thru the secretion of:
- mucus
- bicarb
- prostaglandins
how does mucus provide protection
- protective barrier against HCl
how does bicarb provide protection
- helps buffer acidic properties of HCl
how do prostaglandins provide protection
- prevent activation of the proton pump & stimulates mucus production
describe the onset of antacids
- typically very quick
list 4 different types of antacids
- aluminum salts
- magnesium salts
- calcium salts
- sodium bicarb
how are antacids used?
- used alone or in combo with each other
what is the main side effect of aluminum salts
- constipation
how is the side effect of aluminum salts avoided? how does this work?
- often used with magnesium to counteract constipation
- a side effect of magnesium is diarrhea = cancel each other out
what type of patients are aluminum salts often recommended for? why?
- pts with renal disease
- bc they are more easily excreted
what is an example of an aluminum salt
- aluminum hydroxide salt = amphojel
what is a common side effect of magnesium salts? how is this avoided?
- diarrhea
- often combined w other drugs to counteract this effect
what kind of patients should magnesium salts not be used in? why?
- in pts with renal failure
- bc the failing kidney cannot excrete extra magnesium = accumulation
list 2 examples of magnesium salts
- magnesium hydroxide (milk of magnesia)
- magnesium carbonate = gaviscon ( can also be a combo)
what are 2 examples of magnesium combo products
- Maalox & Mylanta (aluminum & magnesium)
what is the most common form of calcium salts
- calcium carbonate
what are 2 side effects of calcium salts
- constipation
- kidney stones
how can calcium salts cause kidney stones
- bc too much calcium can lead to the development
what kind of patients should calcium salts not be used in? why?
- not recommended for pts with renal disease
- bc may accumulate to toxic lvls
describe the duration of calcium salts; what does this cause? how?
- long duration of acid action
- this can cause hyperacidity rebound
- bc the acid secretion is being blocked for so long, the stomach produces a ton of gastrin to try and compensate. so once the individual stops taking the med, all of that gastrin can suddenly trigger acid production
what are calcium salts often advertised as
- an extra source of dietary calcium
what is an example of calcium salts
- tums = calcium carbonate
what is the MOA of histamine type 2 antagonsist (2)
- reduce acid secretion by blocking the action of histamine at the H2 receptors of acid-producing parietal cells
- reduce the production of H+ ions = reduced HCl
how are H2 antagonists available?
- all available OTC in lower dosage forms
how effective are H2 antagonists
- provide a 25-75% decrease in acid production
list 1 example of H2 antagonists
- ranitidine (Zantac)
what is the most popular drug for treatment of acid-related disorders
H2 antagonists
what is a drug interaction associated eith H2 antagonists
- smoking decreases the effectiveness of H2 blockers
what is the MOA of proton pump inhibitors
- irreversibly bind to H+/K+ ATPase enzyme (which are responsible for the proton pump)
- this bond prevents the movement of H+ ions from the parietal cell into the stomach
how effective are proton pump inhibitors
block 100% of acid production for 24h
what do proton pump inhibitors result in? what is this?
- achlorhydria
- ALL gastric acid secretion is temporily blocked
what must happen for the cell to return to normal acid secretion after treatment w a proton pump inhibitor
- the parietal cell must synthesize new H+/K+ ATPase
- which takes ~1 day
what is an example of a proton pump inhibitor
- omeprazole (prilosec or Losec)
describe the short term adverse effect of proton pump inhibitors
- HA
- diarrhea
- NV
describe the long term side effects of proton pump inhibitors (3)
- pneumonia
- fractures (low) due to low calcium absorption
- rebound hypersecretion
what is a fear associated with proton pump inhibitors
- fear of increased risk of infection (lack of acid could cause bacteria overgrowth)
list 2 miscellaneous peptic ulcer drugs
- sucralfate (carafate)
- misoprostol (cytotec)
what is sucralfate
- coating agent & cytoprotective drug
what is sucralfate used for
- stress ulcers
- peptic ulcer disease
what is the MOA of sucralfate
- attracted to & binds to the base of ulcers & erosions, forming a protective barrier over these areas
- protects these areas from pepsin = prevents the ulcers from worsening
what is misoprostol
- synthetic prostaglandin analog
= can artifically restore prostaglandin cytoprotective activity
describe the cytoprotective activity of prostaglandin (4)
- protect gastric mucosa from injury by enhancing local production of mucus
- inhibits acid production at higher doses
- promotes local cell regeneration
- helps maintain mucosal blood flow
what is misoprostol specifically used for
- prevention of NSAID induced gastric ulcers
describe side effects of misoprostol
doses that are therapeutic enough to treat duodenal ulcers often produce:
- abdominal cramps
- diarrhea
describe the side effects of H2 receptor antagonists
- very few
- may increase risk of aspiration
what is one thing to consider with antacids
- give one hour apart from H2 antagonists and sulcrafate
describe the general safety of proton pump inhibitors
- generally v safe & tolerated well with few side effects
