GI Part 1 Flashcards
Meds that can cause constipation
- Opioids
- Anticholinergics
- Antacids w/Al or Ca
- CCBs
- Thiazides
- Iron supplements
- NSAIDs
When should meds be taken when treating constipation?
At bedtime
What MOAs are there to treat constipation?
- Soften stool
- Ease passage (lubricants)
- Add bulk to stool
- Stimulate GI tract
- Stimulate GI secretory process
- Increase GI motility
How do stool softeners work?
- Anionic surfactants
- Detergents that mix aqueous and fatty substances
- Fecal mass is softened
How do stool softeners help constipation?
- Prevention
- Softens fecal mass
- Avoids straining
Onset of stool softeners?
1-3 days
How are stool softeners given?
Often combined with other agents
Example of a stool softener
Docusate (Colace)
How do lubricants work in constipation?
- Coats stool and prevents absorption of water
- Easier passage
Onset of lubricants?
24 hours
What is glycerin, its use, and its onset?
- Lubricant for constipation
- Suppositories sized for infant, kids or adults
- Commonly used in children
- 30 min onset
What lubricant is MC used in children for constipation?
Glycerin
Features of mineral oil
- Lubricant for constipation
- Avoid in bedridden pts bc of aspiration pneumonia
- Can affect absorption of fat soluble vitamins, warfarin, OCPs
- Avoid long term use
How do bulk forming agents work?
- Adds bulk to feces
- Promotes peristalsis
How should bulking agents be given?
- Take w/lots o’ liquids!
- Do NOT use in bedridden pts
- Separate other meds by 1-2 hrs
Onset of bulking agents?
1-3 days
Side effects of bulking agents
Bloating and gas
Examples of bulking agents
- Psyllium (Metamucil)
- Benefiber, Bran (dietary)
What are osmotic bulking agents and how do they work?
- Nonabsorbable sugars
- Prevention and treatment of chronic constipation
- Pull water into colon, soften stool, increase volume
- Lactulose and 33% sorbitol
What is lactulose?
- Osmotic bulking agent for constipation
- Onset 1-3 days
What is 33% sorbitol?
- Osmotic bulking agent for constipation
- Quick effect
What are saline cathartics and how do they work?
- Bulking agent for constipation
- Nonabsorbable cations and anions
- Pull fluid into GI tract
- Milk of Magnesia, Sodium Phosphate
How are saline cathartics used to treat constipation?
- Occasional use! Every few weeks
- Take adequate fluids with it
- 6 hour onset
What are electrolyte solutions and how do they work?
- Bulking agent for constipation
- Polyethylene Glycol (PEG)
- Nonabsorbable osmotically active sugar
- Draws water into GI lumen
What is PEG and how is it used?
- Polyethylene Glycol (bulking agent)
- Used to treat constipation
- Used for colonic cleaning prior to diagnostic procedures
What is PEG 3350?
- MiraLax, electrolyte bulking agent for constipation
- Powder mixed in liquid
- Fewer side effects than other laxatives
- No prescription needed
- Can give w/narcotics
What are GI stimulants and how are they used?
- Directly stimulates intestinal peristalsis through local mucosal irritation
- Used to treat constipation
- Can give w/narcotics
- Bisacodyl (Ducolax), Senna
What type of GI stimulant is Bisacodyl (Ducolax)?
Diphenylmethane derivative
What type of GI stimulant is Senna?
Anthraquinone derivative
Onset of oral GI stimulant vs. rectal GI stimulant?
Oral 6-12 hrs
Rectal 15-60 mins
What are GI secretory agents and how are they used?
- Stimulates secretion of fluid into gut, strong purgative action
- Used for constipation (NOT regularly)
- Onset 1-3 hours
- Castor oil
What is castor oil and how is it used?
- GI secretory agent for constipation
- NOT for regular use
What are GI motility stimulants and how are they used?
- Prescription agents to increase colonic motility and shorten transit time
- Used for constipation
- Metoclopramide (Reglan)
What is metoclopramide (Reglan) and how is it used?
- GI motility stimulant for constipation
- Dopamine antagonist
- Variable results
- Onset 6-48 hours
Which patients are most affected by opioid induced constipation?
- Cancer pain (95%)
- Nonmalignant pain (80%)
Pathophys of opioid-induced constipation
Results from action on mu-opioid receptors in the GI tract (decreased motility, secretions, defecation)
What are the targeted therapies of constipation?
- Mu opioid receptor blockers
- Chloride channel activators
How do mu-opioid receptor antagonists work?
- Inhibit peripheral receptors without affecting the analgesic effects of opioids
- Do NOT cross BBB
- Wake up the bowel
- Methylnaltrexone (Relistor)
What is methylnaltrexone (Relistor) and how is it used?
- 2nd line treatment after laxatives of opioid induced constipation
- SQ injection
- Onset within 4 hours
What is naloxegol (Movantik) and what does it do?
- New mu opioid receptor blocker
- Available oral (unlike Relistor)
- Minimal risk of counteracting analgesic effects of opioids
- CYP3A4 metabolism
What is the chloride channel activator and how is it used?
- Lubiprostone (Amitiza)
- Stimulates Type 2 chloride channels in small intestine
- Used for: chronic idiopathic constipation, IBS in women, OIC
What is Lubiprostone?
- Chloride channel activator
- Used for: chronic idiopathic constipation, IBS in women, OIC
- Onset usually within 24 hrs
- Nausea common due to delayed emptying
Meds that can cause diarrhea
- PPIs
- Antacids w/magnesium
- Digoxin
- Abx (clinda, tetra, augmentin)
- ACEI
- NSAIDs
Non-pharm treatment of diarrhea
- BRAT diet
- Hold laxatives and other contributing meds
- Replenish fluids
Use of oral rehydration products in diarrhea
- Available as premixed solutions
- Pedialyte MC
How do oral rehydration products differ?
- Osmolality
- Carb load
- Calories
- Electrolytes
What drug classes are used to treat diarrhea?
- Antimotility
- Adsorbents
- Antisecretory
- Anticholinergics
- Microflora replacement
How do antimotility agents work and what are they used for?
- Stimulate mu-opioid receptors to reduce intestinal motility, slow flow of liquid, and increase absorption
- Used in acute or chronic diarrhea
When are antimotility agents contraindicated?
Bloody or infectious diarrhea
How should antimotility agents be given?
- Cautiously: addiction potential
- NOT recommended in children under 6 yo
Examples of antimotility agents
- Loperamide (Imodium)
- Diphenoxylate w/atropine (Lomotil)
- DTO
What is kaolin-pectin and how is it used?
- Adsorbent agent for traveler’s diarrhea
- Adsorbs bacteria, toxins, fluid
- Decreases stool liquidity and frequency
- May reduce absorption of some meds like warfarin
What meds are used for traveler’s diarrhea?
- Kaolin-pectin (adsorbent)
- Bismuth subsalicylate (antisecretory)
What is bismuth subsalicylate and how is it used?
- Pepto Bismol
- Antisecretory and adsorbent
- Anti-inflammatory and antibacterial
- Used in traveler’s diarrhea
What should you be aware of regarding pepto-bismol?
Can blacken tongue and/or stool
What are antisecretory agents used in diarrhea?
- Bismuth subsalicylate (Pepto Bismol)
- Octreotide
What is octreotide and how is it used?
- Synthetic somatostatin
- Antisecretory agent
- Useful in secretory type diarrhea (carcinoid, VIPoma)
What happens with increased dosage of octreotide?
- Inhibits GI motility
- Used for diarrhea caused by short bowel syndrome or AIDS
What happens with decreased dosage of octreotide?
-Stimulates motility-Used for diarrhea w/small bowel bacterial overgrowth or scleroderma
ADRs of octreotide
- Hyperglycemia
- Impaired fat absorption
What is Lomotil and Dicyclomine? What are they used for?
- Anticholinergic agents
- Used in IBS
- Decrease vagal tone, prolong gut transit time
What are microflora replacements and what are they used for?
- Probiotics
- Nonpathologic bacteria that can restore normal GI flora
- Used for variety of causes of diarrhea
- Activia yogurt, Lactobacillus
What components protect the stomach lining from acid damage?
- Mucus and bicarb secretions
- Prostaglandins
What meds can cause GERD?
- NSAIDs
- Bisphosphonates
- CCBs
- Iron
- Potassium
How do antacids work and what are they used for?
- Neutralize acid and raise intragastric pH
- Used for intermittent GERD
- Ca, Mg, Al based agents
Onset of antacids
10 mins (short duration of 1-2 hrs)
ADRs of Ca and Al based antacids
Constipation
ADRs of Mg based antacids
Diarrhea
Antacids drug interactions
- Chelation (binding): Fluoroquinolones
- Increases pH and reduces absorption (Itraconazole, Iron)
What are H2 blockers?
- Compete with histamine at H2 receptors on parietal cells to suppress acid secretion
- Used for GERD
Which GERD/PUD drug class is most effective for reducing nocturnal acid?
H2 blockers
ADRs of H2 blockers
- Minimal (HA, dizzy, diarrhea/constipation)
- Cimedtidine: increase in prolactin, may see gynecomastia/galactorrhea
When is H2 blocker dosing adjusted?
Moderate to severe renal impairment OR elderly
Limitations of H2 blockers
- Tolerance
- Not effective in H pylori ulcers
- Avoid in pregnancy
- Less potent than PPIs
- Drug interactions
Which H2 blocker has the most drug interactions?
Cimetidine
Describe PPIs
- Inhibit acid secretion for up to 24 hours
- Omeprazole, pantoprazole, etc.
- More effective than H2 blockers
- All are equally effective and tolerance does not develop
Safety concerns of PPIs
- May increase fracture risk
- May decrease absorption of Mg and B12
- Increase risk of infection (disruption of acid barrier)
Describe sucralfate
- Aluminum salt of sulfated disaccharide that combines w/protein
- Adheres to base of ulcer and forms a barrier to acid and pepsin
- Stimulates PG release and mucus/bicarb secretion
What are prostaglandin analogs?
- Synthetic PG
- Stimulate production of mucus and bicarb (protective against acid)
- Misoprostal (PGE1)
What is Misoprostal?
- Synthetic PG
- Decreases incidence of NSAID related ulcers (PPIs are still better though)
- Severe GI side effects
- Preg Cat X (stimulates uterine contractions)
Describe bismuth salts
- Unclear MOA: no acid inhibitory effects, but antimicrobial
- Treatment of H pylori
- Pepto Bismol
What is Metoclopramide?
- Motility agent
- Stimulates upper GI tract without increasing acid secretion
- Central acting anti-nausea and anti-emetic
- Given multiple times/day
- Numerous side effects
What is Metoclopramide used for?
- Given with PPI to reduce heartburn with GERD
- Enhances gastric emptying in post-op pts
How are high risk pts treated for chemo induced N/V?
NK1 antagonist, 5HT3 antagonist AND corticosteroid
How are moderate risk pts treated for chemo induced N/V?
Dopamine antagonist AND corticosteroid
How are low risk pts treated for chemo induced N/V?
Corticosteroid alone
What is acute CINV?
0-24 hrs after chemo
What is delayed CINV?
24+ hrs after chemo
What are 5HT3 antagonists?
- Serotonin blockers (central and peripheral)
- Used for CINV, PONV, RINV
- Ondansetron (Zofran)
- All available PO/IV
Do 5HT3 antagonists treat acute or delayed CINV?
Acute more than delayed (give before chemo)
Side effects of 5HT3 blockers?
- Constipation, mild HA
- Potential QT prolongation
What are NK-1 antagonists used for?
- Prevention of acute and delayed NV
- Given as a 3 day regimen (IV then PO 2 days)
- CYP interactions
- Apreptitant
Corticosteroids used in NV treatment and how do they work?
- Dexamethasone
- Methylprednsiolone
- MOA unclear
- Acute or delayed CINV
What are dopamine antagonists used for?
- Delayed CINV
- Moderate to low emetogenic chemo
- Lower potency
- Prochlorperazine, promethazine
What are benzodiazepines used for?
- Prevent anticipatory CINV
- No antiemetic properties, good if want to sleep through the NV
- Lorazepam
What are cannabinoids used for?
- Refractory, delayed CINV
- Medical marijuana
What are antihistamines used for?
- H1 blockers
- Used for motion sickness
- SHORT trips
- Weak anticholinergic activity
Which motion sickness meds are used for short trips vs. long trips?
- Short: antihistamines
- Long: anticholinergic
What is scopolamine?
- Anticholinergic used for motion sickness of long trips
- Patch behind ear at least 3 hrs before exposure and reapply every 3 days
