Pharm - GI Potpourri Flashcards
What are the salts commonly used in antacids?
- Mg++ salts
- Al++ salts
- Ca++ carbonate
ADRs Mg salts
- diarrhea
- avoid in renal dysfunction
ADRs of Al salts and Ca carbonate
- constipation
- avoid in renal dysfunction
What is the place in therapy in the tx of GERD for antacids?
- used for pts w/ mild/intermittent sx
- can be taken on an “as needed” basis
MoA of antacids
- weak bases that neutralize gastric acid to form salt and water
- also enhance GI mucosal defenses by stimulating prostaglandin production or binding substances that may be toxic
onset and duration of antacids
- rapid onset
- short duration: 30min - 3 hrs
counseling points for antacids
- separate by 2 hrs from tetracyclines and fluoroquinolones
- take 1 hr following a meal for most relief
What are the H2 receptor antagonist (H2RAs) products?
- famotidine (pepcid)
- ranitidine (zantac) - preferred in pregnancy
- nizatidine (axid)
- cimetidine (tagamet)
What is H2RA dosing based on?
a low dose (OTC) and standard dose (Rx)
common ADR of H2RAs
tachyphylaxis (body learns how to work around it)
place in therapy for H2RAs in the tx of GERD
- effective for mild to moderate GERD
- can be used on an “as needed” basis
MoA of H2RAs
- reversible**, competitive antagonist of histamine at the H2 receptor on the membrane of acid-secreting parietal cells
- selective for H2, does not effect H1
onset and duration of H2RAs
- slower onset compared to antacids
- reaches peak at 2.5 hrs but duration is 4-10 hrs
counseling points for H2RAs
- faster osnet than PPIs, but tolerance develops
- use has declined since intro of PPIs
- pregnancy category B
What is the drug of choice for the tx of moderate to severe GERD and PUD?
-PPIs: omeprazole
ADRs of PPIs
-these are important to know
- infections: c. diff, pneumonia
- malabsorption
- kidney dz
- drug induced lupus
- mortality
what malabsorption risks occur in using a PPI?
- mild reduction in iron
- mild reduction in B12
- significant impairment of magnesium absorption - hypomagnesemia
- significant impairment of Ca absorption
what is the place in therapy for PPIs in the tx of GERD?
drug of choice in moderate-severe GERD
MoA of PPIs
- irreversibly inhibits H+/K+ ATPase (proton pump) in the gastric parietal cell
- prodrugs
- irreversible and covalently bound so very powerful
onset and duration of PPIs
-more potent and longer lasting than H2RAs
counseling points for PPIs
- take 30 min before meals
- usually taken in the morning but can be taken at night if nighttime sx
- administer daily, not “as needed”
drug interactions of PPIs
-omeprazole and clopidigrel** b/c omeprazole inhibits CYP2C19
what are the PPI products available?
- omeprazole (prilosec) (one we have to know)
- lansoprazole (prevacid)
- dexlansoprzole (dexilant)
- esomeprazole (nexium)
- pantoprazole (protonix)
- rabeprazole (aciphex)
- omeprazole/sodium bicarb (Zegerid)
Al hydroxide / sucrose sulfate product
-sucralfate (carafate)
sucralfate place in therapy for the tx of GERD
-most commonly used in the tx of and prevention of PUD
MoA of sucralfate
- forms viscous gel in the presence of acid
- adheres to epithelial cells and ulcers creating a barrier
- enhances GI mucosal protective factors
lifestyle modifications for the tx of GERD
- elevate head of bed (esp if night sx)
- weight reduction in obese pts
- avoid: fats, chocolate, alcohol, peppermint/spearmint
- avoid: spicy foods, OJ, tomato juice, coffee
- eat small meals
- avoid eating immediately prior to sleeping
- stop smoking
- avoid tight fitting clothes
drugs to avoid in GERD
- drugs that have a direct irritant effect on esophageal mucosa
- bisphosphonates
- tetracylcines
- K+Cl
- iron salts
- aspirin
- NSAIDs
- if can’t be avoided: take w/ plenty of liquid
Tx of mild/intermittent GERD? And what is the appropriate step up therapy?
- lifestyle modifications
- PRN low dose H2RAs and/or antacids
- increase to standard dose of H2RAs for 2 wks
- if still not working, dc H2RA and start PPI (8 weeks max)
tx of severe/frequent sx of GERD or erosive esophagitis
-start w/ standard dose PPI daily for 8 weeks plus lifestyle change
management of recurrent sx and maintenance therapy of GERD
- many pts relapse when acid acid suppression is dc
- all GERD pts should have a trial off meds unless they have erosive esophagitis, they should remain on PPI
- pts w/ recurrent sx should be managed w/ same tx
given a pt w/ h. pylori, what is the first line combo tx for PUD?
- bismuth quadruple therapy:
- drug 1: omeprazole 20 mg po BID
- drug 2: bismuth subsalicylate (525 mg QID)
- drug 3: metronidazole 250-500 mg QID
- drug 4: tetracycline 500 mg QID
what is the duration of tx for the bismuth quadruple regimen for tx of PUD d/t h. pylori?
10-14 days
given a pt w/ h. pylori, what is another first line combo tx for PUD?
- concomitant regimen
- drug 1: omeprazole 20 mg po BID
- drug 2: clarithyomycin 500 mg po BID
- drug 3: metronidazole 250-500 mg QID
- drug 4: amoxicillin 1 g BID
what are the reasons for tx failure in PUD?
- poor compliance
- resistance of h. pylori strain
- clarithromycin resistance
- prior use of macrolide abx, metronidazole, and levoflaxacin increases risk of resistnace
what is the approach to salvage therapy when tx of PUD d/y h. pylori has failed?
- abx choice should be guided by pts initial tx
- can increase Bismuth quadruple therapy to 14 days
- levofloxacin triple therapy for 10 days
- high dose dual therapy for 14 days
- last resort: rifabutin therapy
levofloxacin triple therapy for salvage tx
- levofloxacin
- amoxicillin
- PPI
- 10-14 days
high dose dual therapy for salvage tx
- amoxicillin 1 g TID (or 750 mg QID)
- PPI
- 14 days
rifabutin therapy for salvage tx
- rifabutin 150 mg BID
- amoxicillin 1 gm BID
- PPI BID
- 10 days
What are the classes of med used to tx n/v
- dopamine receptor antagonists
- 1st generation H1 antagonists
- anticholinergics
- serotonin (5-HT3) antagonists
dopamine receptor antagonists
- prochlorperazine (compazine, compro)
- metoclopramide (reglan)
1st generation H1 antagonists
- dimenhydrinate (dramamine)
- promethazine (phenergan)
- meclizine (antiver, bonine)
anticholinergics
-scopolomine (transderm scop)
serotonin (5-HT3) antagonists
-ondansetron (zofran)
ADR of prochlorperazine
- **cardiac arrhythmias (QT prolongation, torsades)
- **extrapyramidal sx
- hypotension
- sedation
- neuroleptic malignant syndrome
ADR of metoclopramide (reglan)
- extrapyramidal syndrome
- sedation
- tardive dyskinesia
- acute dystonic reactions
- nausea
- galactorrhea
contraindications of metoclopramide (reglan)
- GI obstruction/perforation, concurrent drugs that can cause extrapyramidal syndrome, hx of seizures
- black box warning: irreversible tardive dyskinesia w/ higher dosing and long term use
general ADRs of the first generation H1 antagonists
- anticholinergic
- CNS depression
- confusion
- sedation
- constipation
- dry mouth
- urinary retention
- blurred vision
*promethazine: EPS
ADRs of scopolomine
- orthostatic hypotension
- zerostomia
- blurred vision
- constipation
- urinary retention
ADRs of serotonin antagonists
- QT prolongation (at higher doses)
- contipation
- abdominal pain
- HA
- sedation
- zerostomia
- blurred vision
- fatigue
What med classes are used in the tx of constipation?
- stimulants
- stool softener
- osmotic laxative
- bulk forming agents
stimulants
- bisacodyl
- senna
stool softeners
-docusate sodium/docusate calcium
osmotic laxative
- magnesium salts (hydroxide, citrate)
- sodium phosphates (fleet)
- glycerin (fleet)
- lactulose
- polyethlyn glycol (miralax)
bulk forming agents
- psyllium (metamucil)
- polycarbophil calcium (fibercon)
bulk forming agent (psyllium) MoA
soluble fiber that absorbs water in the intestine to form a viscous liquid to promote peristalsis and reduce transit time
magnesium salts (osmotic laxative) MoA
-osmotically increases water content of feces and fluid volume in the intestinal lumen resulting in increased intraluminal pressure
which exerts a mechanical force to stimulate peristalsis
polyethylene glycol (miralax) (osmotic laxative) MoA
osmotically retains water to produce laxation
stool softener/docusate sodium MoA
surfactants that reduce the surface tension and allow intestinal fluids and fatty substances to penetrate the fecal material
stimulants MoA
- act as local irritant of intestinal mucosa
- increase propulsive activity
- increase motility by selective action on intramural nerve plexus
- increase mucosal permeability resulting in movement of fluid and electrolytes into intestinal lumen
What is the general approach in the tx of constipation?
- good hx is key
- look at all things before starting tx: drug cuases, diseases, lifestyle
- start w/ bulk forming agent
- then can go to osmotic laxative
- can add stimulant or use as rescue
what med classes are used in the tx of diarrhea?
- adsorbents:
- bismuth subsalicylate (pepto-bismol)
- opiods:
- loperamide (imodium)
- diphenoxylate/atropine (lomotil)
pepto bismol MoA
- bismuth has direct antimicrobial effects and binds enterotoxins
- salicylate component is thought to inhibit intestinal prostaglandin and chloride secretion
- leads to reduced stool frequency and liquidity
loperamide (imodium) MoA
- slows intestinal transit
- enhances water and electrolyte absorption and strengthens rectal sphincter tone
diphenoxylate/atropine (lomotil) MoA
-diphenoxylate inhibits excessive GI motility and propulsion
What is the appropraite tx regimen to prevent traveler’s diarrhea?
- CDC no longer recommends prophylaxis d/t resistance and ADRs
- can be considered in pts at high risk of complications d/t dehydration (IBD, sever vascular, renal or cardiac dz, or immunocompromised)
- non pharmacologic: common sense, avoid ice, certain foods, safe water, “boil it cook it peel it or forget it” and rule of “Ps”
What is the tx regiment to tx traveler’s diarrhea?
- fluid replacement - important
- restricted diet (clear liquids)
- abx:
- fluoroquinolones
- azithromycin
- rifaxamin
- loperamid w/ abx
- bismuch subsalicylate
What med classes are used to provide symptomatic relief of hemorrhoids?
- topical analgesics and steroids: for acute pain and shrinking
- vasoactive agents: reduce swelling
- antispasmotic agents: reduce spasms
- sitz bath: relive inflammation/edema and relax muscles; releive pruritis
- protectants
- astringents
role of a low FODMAP diet in IBS
- only one w/ evidence
- eliminate FODMAPs for 6-8 weeks then gradual reintroduction to determine tolerance
- has been shown to improved IBS sx (abd pain, bloating, flatulence and dissatisfaction w/ stool consistency)
Given a pt w/ IBS-C, what is the appropriate tx regimen?
- Fiber: increase in dietary fiber, supplementation, or both.
- If not responsive to fiber, add osmotic laxative.
- If 1+2 didn’t work, consider lubiprostone (Amitiza) or linaclotide (linzess)
Fiber supplementation in IBS-C
- start low then increase dose
- use soluble
- psyllium (metamucil) is preferred
Given a pt w/ IBS-D, what is the appropriate tx regimen?
- dietary modification
- loperamide (imodium) - needs to be dosed regularly
- Viberzi - controlled substance, contraindicated if pt doesn’t have GB
- in pts w/ persistent diarrhea despite antidiarrheals, consider bile acid sequestrants
What is the max dose of loperamide (imodium)?
16 mg/day
What are the meds used to tx pain and bloating in IBS?
- dietary modification
- antispasmodics/anticholinergics:
- dicyclomine (Bentyl)
- hyoscyamine (Anaspaz, Levsin)
