GI Motility 2 Flashcards
Which laxative?
- rapid movement of water into the distal small bowel and colon leads to a high volume of liquid stool followed by rapid relief of constipation
- high doses of osmotically active agents produce prompt bowel evacuation within 1–3 hours
- important that patients maintain adequate hydration by taking increased oral liquids to compensate for fecal fluid loss
Purgatives (Osmotic - nonabsorbably sugars/salts)
- Magnesium citrate
- Sodium phosphate
ADEs of which laxative?
- hyperphosphatemia
- hypernatremia
- hypocalcemia
- hypokalemia
- may lead to cardiac arrhythmias
- may lead to acute renal failure due to tubular deposition of calcium phosphate (nephrocalcinosis)
Sodium Phosphate
(Purgative - Osmotic - Nonabsorbable sugars/salts)
In which 4 patients should you not prescribe Sodium Phosphate?
(Purgative - Osmotic - Nonabsorbable sugars/salts)
- Frail / elderly
- Renal insufficiency
- Significant cardiac disease
- Unable to maintain adequate hydration during bowel preparation
Which laxative?
- complete colonic cleansing before gastrointestinal endoscopic procedures
- balanced, isotonic solutions contain an inert, nonabsorbable, osmotically active sugar with sodium sulfate, sodium chloride, sodium bicarbonate, and potassium chloride
- designed so that no significant intravascular fluid or electrolyte shifts occur
Polyethylene glycol (PEG)
Which laxative?
- safe for all patients
- solution should be ingested rapidly (2–4 L over 2–4 hours) to promote bowel cleansing
- treatment or prevention of chronic constipation
- smaller doses of this powder may be mixed with water or juices (17 g/8 oz) and ingested daily
- does not produce significant cramps or flatus
Polyethylene Glycol (PEG)
(MiraLAX)
Which laxative?
- Induce bowel movements through direct stimulation of the enteric nervous system and colonic electrolyte and fluid secretion
- may be required on a long-term basis
- Neurologically impaired
- Bed-bound patients in long-term care facilities
Cathartics (stimulant laxatives)
Which laxative?
- Long-term use is controversial
- Newer studies do not report damage to the enteric nervous system like earlier studies
- Nerve damage may be the cause of the constipation rather than the result of using laxatives
- Patients requiring regular use of laxatives may still need to be monitored for these effects
Stimulant laxatives (cathartics)
Which laxative?
- Aloe, senna, and cascara
- Occur naturally in plant
- Laxatives are poorly absorbed and after hydrolysis in the colon, produce a bowel movement in 6–12 hours when given orally and within 2 hours when given rectally
Anthraquinone Derivatives
(Laxative Stimulants)
Anthraquinone Derivatives (Laxative Stimulant)
- Chronic use causes what?
- There is concern these agents may cause what?
- Characteristic brown pigmentation of the colon (Melanosis Coli)
- Carcinogenic, but epidemiologic studies do NOT suggest a relation to colorectal cancer
Which laxative?
- Bisacodyl (Ducolax)
- treatment of acute and chronic constipation
- used in conjunction with PEG solutions for colonic cleansing prior to colonoscopy
- induces a bowel movement within 6–10 hours when given orally and 30–60 minutes when taken rectally
- minimal systemic absorption and appears to be safe for acute and long-term use**
Diphenylmethane Derivative
Acute and Chronic therapy w/ opioids may cause constipation due to what mechanism?
Decreasing intestinal motility, which results in prolonged transit time & increased absorption of fecal water
Which 3 Opioid Receptor Antagonists (peripherally acting)?
- do not readily cross the blood-brain barrier
- inhibit peripheral μ-opioid receptors without impacting analgesic effects within the central nervous system
- Methylnaltrexone bromide
- Alvinopan
- Naloxegol
Which Opioid Receptor Antagonist?
- approved for the treatment of opioid-induced constipation in patients receiving palliative care for advanced illness who have had inadequate response to other agents
- Dosage adjustment with severe renal impairment (CrCl < 30ml/min)
Methylnaltrexone (Relistor)
Which Opioid Receptor Antagonist?
- approved for short-term use to shorten the period of postoperative ileus in hospitalized patients who have undergone small or large bowel resection
- no more than 7 days
- possible cardiovascular toxicity
Alvimopan (Entereg)
Which Opioid Receptor Antagonist?
- Opioid-induced constipation
- Dosage adjustment with renal impairment (CrCl < 60ml/min)
- Avoid use in severe hepatic impairment (Child-Pugh class C)
- Contraindicated in patients with GI obstruction
Naloxegol (Movantik)
Name a few drugs which cause diarrhea
- Laxatives (duh)
- Auranofin (gold salt)
- Antibiotics (Clinda, tetracyclines, Sulfonamides, any broad spectrum)
- Antihypertensives
- Cholinergics
- Cardiac agents (digoxin)
- NSAIDs
- Misoprostol
- PPIs
- Acute diarrhea is how many days?
- Chronic diarrhea is how many days?
- Acute: <3 days
- Chronic: >14 days
Clinical Controversy
- Withholding food is considered inappropriate in pts w/ no signs of what?
- In osmotic diarrhea, what may control the problem?
- If the mechanism is ____, diarrhea persists
- Severe dehydration
- food
- secretory
What type of Antidiarrheal Agent?
- Antimotility
Opioid agonists
What type of Antidiarrheal Agent?
- Kaolin-pectin mixture
Absorbents
What type of Antidiarrheal Agent?
- Colloidal Bismuth Compounds
- Bile Salt-Binding Resins
- Octrotide
Antisecretory
What are the 4 types of Antidiarrheal Agents
- Antimotility
- Adsorbents
- Antisecretory
- Bacterial replacement and enzymes
Antidiarrheal Agents
- Safe to use for mild to moderate acute diarrhea
- Should not be used in patients w/ what 3 things?
- Due to risk of worsening the underlying condition?
- Discontinue in pts whose diarrhea is worsening despite therapy
- Bloody diarrhea
- High fever
- Systemic toxicity
Antidiarrheals are used to treat which 2 conditions?
IBS and IBD
Which antidiarrheal agent?
- significant constipating effects
- increase colonic phasic segmenting activity through inhibition of presynaptic cholinergic nerves in the submucosal and myenteric plexuses and lead to increased colonic transit time and fecal water absorption
- decrease mass colonic movements and the gastrocolic reflex
Opioid Agonists
Which antidiarrheal agent?
- nonprescription opioid agonist
- does not cross the blood-brain barrier
- no analgesic properties or potential for addiction
- tolerance to long-term use has not been reported
- administered in doses of 2 mg taken one to four times daily
Loperamide
Which antidiarrheal agent?
- prescription opioid agonist
- no analgesic properties in standard doses
- higher doses have central nervous system effects
- prolonged use can lead to opioid dependence
Diphenoxylate
Which antidiarrheal agent?
- Commercial preparations commonly contain small amounts of atropine to discourage overdosage (2.5 mg diphenoxylate with 0.025 mg atropine)
- anticholinergic properties of atropine may contribute to the antidiarrheal action
Diphenoxylate
What type of antidiarrheal agent?
- Kaolin-pectin
- Polycarbophil
- Attapulgite (removed from market)
- Effectiveness unproven
- Adsorb nutrients, toxins, drugs, and digestive juices
Adsorbents
Which antidiarrheal agent?
- Mucosal Protective Agents
Colloidal Bismuth Compounds
Bile Salt-Binding Resins
- Conjugated bile salts are normally absorbed where?
- Disease of this location (Crohn’s Disease) or surgical resection leads to malabsorption of bile salts, which may cause what?
- terminal ileum
- colonic secretory diarrhea
What are the 3 names of the Bile Salt Binding Resins?
- cholestyramine
- colestipol
- colesevelam
Which antidiarrheal agent?
- decrease diarrhea caused by excess fecal bile acids
- powder and pill formulations that may be taken one to three times daily before meals
Bile Salt Binding Resins
- Cholestyramine
- Colestipol
- Colesevelam
4 ADEs of Bile Salt Binding Resins
- bloating
- flatulence
- constipation
- fecal impaction
Bile Salt Binding Resins
- Patients w/ diminished circulating bile acid pools, further removal of bile acids may lead to what?
exacerbation of fat malabsorption
Which 2 Bile Salt Binding Resins?
- bind a number of drugs and reduce their absorption
- not be given within 2 hours of other drugs
- Cholestyramine
- Colestipol
Which Bile Salt Binding Resin?
- does not appear to have significant effects on absorption of other drugs
Colesevelam
Antisecretory : Octreotide
Which drug?
- 14-amino-acid peptide released in the gastrointestinal tract and pancreas from paracrine cells, D cells, and enteric nerves as well as from the hypothalamus
Somatostatin
What are the 3 key regulatory peptide physiologic effects of Somatostatin?
- inhibits the secretion of numerous hormones and transmitters (gastrin, glucagon. insulin)
- reduces intestinal fluid secretion and pancreatic secretion
- slows gastrointestinal motility and inhibits gallbladder contraction
Which drug?
- reduces portal and splanchnic blood flow.
- inhibits secretion of some anterior pituitary hormones.
- clinical usefulness is limited by its short half-life in the circulation (3 minutes) when it is administered by intravenous injection
Somatostatin
Which drug?
- Inhibition of Endocrine Tumor Effects
- Two gastrointestinal neuroendocrine tumors (carcinoid, VIPoma) cause secretory diarrhea and systemic symptoms such as flushing and wheezing
Somatostatin (Octreotide)
Antisecretory: Octreotide - Somatostatin
- Low doses do what?
- Higher doses do what?
- Higher doses for the tx of diarrhea due to vagotomy or dumping syndrome as well as for diarrhea caused by what 2 conditions?
- Low doses to stimulate small bowel motility in pts w/ small bowel bacterial overgrowth or intestinal pseudo-obstruction secondary to what condition?
- Low: stimulate motility
- Higher: inhibit motility
- short bowel syndrome / AIDs
- Scleroderma
3 “other uses” of Somatostatin (Octreotide - Antisecretory)
- inhibits pancreatic secretion-value in patients with pancreatic fistula
- treatment of pituitary tumors (eg, acromegaly)
- gastrointestinal bleeding (decreases splanchnic blood flow-vapreotide)
ADEs of which drug?
- Steatorrhea (can lead to fat soluble vitamin deficiency)
- sludge or gallstones in over 50% of pts
- hyperglycemia / hypoglycemia (less frequent)
- Hypothyroidism from long term tx
- Bradycardia
Somatostatin (Octreotide - Antisecretory)
