acid/pepsin txt Flashcards
what are the two major groups of drugs for acid/pepsin disorders?
- decrease acid from gastric lumen
2. promote mucosal defense (promote HCO3- secretion)
what are the 3 groups of drugs that decrease acid from gastric lumen?
anatacids, H2 blockers, PPIs
what are the 3 drugs that promote mucosal defense?
prostoglandin analogs (Misoprostol aka Cytotec)
Bismuth (aka Pepto Bismol)
Sucaralfate (aka Carafate)
MOA of antacids
they are all weak bases that react w/ gastric acid to produce H2O and salt.
This raises the pH (decreasing acid effects)
DOA or antacids
2 hours (cover post-mealtime)
how to use antacids: what do they treat? when do you take them? how many times a week can you use them?
treat heartburn/dyspepsia,
take after meals for symptoms
use < 2 days/week
antacids can combine ___ and ___ to decrease ADRs
Al (ADR is constipation)
Mg (ADR is diarrhea)
- antacids may combine these to counteract the ADRs of each
ADRs for antacids: Na+ Al Mg Ca
Na+: burping (which may provide relief), Na+ retention, metabolic alkalosis (rare)
Al: CONSTIPATION, hypophosphatemia
Mg:DIARRHEA, high Mg+
Ca: high Ca++
Antacids: A ffect _____, ______ or _____ of other drugs by altering gastric and urinary pH or by delaying gastric emptying
Affect absorption, bioavailability or urinary excretion of other drugs by altering gastric and urinary pH or by delaying gastric emptying
contraindications for Antacids:
Sodium bicarb
Al and Mg
CHF (for sodium bicarb) renal impairment (Al and Mg ones will accumulate b/c youre not excreting them)
Abx like fluroquinolones, tetracyclines and ketoconazoles are given before or after antacids?
before, they need acidic enviornment for them to work!
what are the four H2 blockers (antagonists) ?
"tidines" Cimetidine (Tagamet) Famotidine (Pepcid) Ranitidine (Zantac) Nizatidine (Axid)
Which H2 blocker has the most ADRs?
Cimetidine (tagamet)
- lots of drug/drug- (warfarin for example)
- imbalance of androgen - prolactin produced =gynecomastia
MOA of H2 blockers
Reversible H2 block on parietal cells
Decreases cAMP = decreased H+ secretion into gastric lumen
PKs of H2 blockers (maybe weeds): Abs, metabolism, 1/2 life, onset, excretion
Absorption-rapid Metabolism-hepatic ½ life – 2 hours; prolonged with renal impairment Onset – 45 min-2 hours Excretion – primarily renal
4 ADRs of H2 blockers (weeds)
- May reduce efficacy of drugs that require an acidic environment for absorption
- CIMETIDINE: DRUG/DRUG, GYNECOMASTIA
- Elderly- confusion after IV administration (dont really know why)
- B-12 deficiency with long term use (although mostly with PPIs)
what do we use H2 blockers for?
mild esophageal reflux (best use for them)
Peptic ulcer
gastritis
which drugs do we use for pregnant pts?
Antacids, then H2, then PPIs
what are the PPI drugs?
"prazoles" Esomeprazole (Nexium) Omeprazole (Prilosec) Lansoprazole (Prevacid) Pantoprazole (Protonix) Rabeprazole (Aciphex) Dexlansoprazole (Dexilant)
MOA of the PPIs, why is this so effective?
Irreversibly binds to H+/K+ ATPase enzyme of parietal cell preventing H+ secretion into gastric lumen
(stop acid secretion at its source! = very effective)
Also, Effective because it take 18 hours for enzyme to be resynthesized
All PPIs are ____, what does this mean?
ALL are Prodrugs: have acid resistant enteric coatings to prevent degradation by gastric acid
Coating removed in alkaline duodenum, prodrug is weak base an is absorbed/taken to parietal cell
PKs of PPIs : abs, onset, 1/2life (weeds)
Rapid absorption
Onset 30 min – 2 hours
½ life – 1-2 hours
why is there a long DOA of PPIs?
Long DOA due to irreversible binding with enzyme
metabolism and excretion for PPIs
Hepatic metabolism
Excretion: urine, feces, bile
3 ADRs of PPIs
- Increased risk of C difficile infection (acidic env. is there to kill Cdiff and we are taking that away)
- hypomagnesemia (increased excretion through GI)
- B-12 deficiency, iron and calcium malabsorption (fracture risk)
what do we use PPIs for?
Peptic ulcer, gastritis, esophageal reflux, H pylori (in combination), stress ulcer prophylaxis, NSAID associated ulcer
when do we take PPIs? why do we take them at this time? (maybe weeds)
Administration: 30-60 minutes before meal
Greatest amount of H+/K+ ATPase enzyme is present after prolonged fast
PPIs for pregnancy? (keep in mind, antacids are class A - aka first choice for pregnant)
omeprazole/esomeprazole class C; all others class B
why do we use PPIs for H pylori?
if we dont irradicate Hpylori, pt is more at risk for certain cancers : we use PPI b/c H pylori in acidic env is dormant (we want it to start replicate so that the abx can target the replicating cyle of the Hpylori)
(wake the monster and kill it !)
what is the controversy of using PPIs on someone taking clopidegrel?
both Omeprazole + Esomeprazole and Clopidegrel are prodrugs- CYP C19 converts both into their active forms -some think if you take them together, the PPI is inhibiting the Clopidegrel but pt may just be poor metabolizers of Clopidegrel!
what is the MOA of sucralfate?
Binds to positively charged proteins of both the normal and necrotic mucosa
- Forms a gel with epithelial cells to create physical barrier
- Protects ulcer from pepsin and acid-promoting healing
overall PKs of sucralafate?
overall: nonsystemic, urine excretion
ADRs of sucralafate?
Aluminum base (which causes constipation) kidney- Al may accumulate if chronic kidney disease
Uses for sucralafate?
duodenal ulcers
Drug/drug problems with most anti- acid-pepsin drugs ?
problem for drugs that need the acidic GI environment to become biologically available.
Sucralafate: Need _____ for activation – shouldn’t be given with ____, ____ or _____
acidic pH
PPI, H2 antagonist, antacids
why is compliance difficult with sucralafate?
QID dosing (4xday)
misoprostol MOA
Prostaglandin E1 analog
binds receptors- slows H/K pump
–>slows acid secretion
–>increase of mucus and HCO3- secretion
misoprostol: Contraindicated in …
pregnancy – induces/augments uterine contractions
however, this can be inserted into cervix, used for induced labor
what do we use for prevention of gastric and duodenal ulcers in patients taking NSAIDs long-term
misoprostol!
PKs of misoprostol (weeds.. not very significant)
Absorption: rapid with onset of action within 30 minutes
Hepatic metabolism
Renal excretion
MOA of bismuth subsalicylate (pepto bismol) (4 parts)
Inhibit proliferation of H pylori
Inhibits activity of pepsin
Increases secretion of mucus
-still unsure of exactly how this one works but we know it interacts with proteins in necrotic tissue to coat/protect ulcers (biggest MOA we care about)
Bismuth Subsalicylate:
Absorption: bismuth-__%; subsalicylate__%
Metabolism: …
Excretion: …
Abs: bismuth: <1% Subsalicylate >80%
metab: converted to bismuth and salicylic acid in GI tract
excretion: bismuth – urine/bile; salicylate- urine
ADR of bismuth subsalicylate
if it works too well… fecal impaction
what do we use Bismuth Sucsalicylate for?
in quadruple therapy for peptic ulcers
what is pepsin?
the chief digestive enzyme in the stomach, which breaks down proteins into polypeptides.
Eradication of H pylori leads to …
rapid healing of ulcer and low recurrence rates
triple and quadruple therapy for H pylori eradication
Triple Therapy
Clarithromycin
Amoxicillin or metronidazole
PPI
Quadruple Therapy Tetracycline Metronidazole Bismuth subsalicylate PPI
what 3 groups of drugs do we use for constipation?
- laxatives (big group)
- Guanylate Cyclase-C (GC-C) Agonist
- Peripherally Acting Mu-Opioid Receptor Antagonist (PAMORA) (for opiod induced consipation)
what are the 6 different groups of laxatives?
- stimulant
- bulk forming
- saline and osmotic
- stool softner
- lubricants
- Cl channel activator
what are the stimulant laxatives? are they Rx or OTC?
Senna (Senokot) (“natural” plant-derived),
bisacodyl (Dulcolax)
castor oil
all OTC
MOA of stimulant laxatives
DIRECTLY STIMULATE NERVE PLEXUS IN COLON to alter water and electrolyte secretion in order to CAUSE PERISTALSIS
onset oral vs suppository for stimulant laxatives?
Onset: oral 6-12 hours; suppositories 1-2 hours