GIT - constipation and diarrhoea Flashcards
Drugs for CONSTIPATION (7)
(BOSS COS)
Bulk-Forming Laxatives - increase water in stools
Osmotic Laxatives - increase water in stools
Stool Surfactant Agents (Softeners) - increase water in stools
Stimulant Laxatives - promote peristalsis/motility
Chloride Channel Activators - promote peristalsis/motility
Opioid Receptor Antagonists - promote peristalsis/motility
Serotonin 5-HT4-Receptor Agonists - promote peristalsis/motility
Bulk forming agents
plant products/ synthetic fibres:
Psyllium
Methylcellulose
Polycarbophil
bulk forming agents MOA
Indigestible, hydrophilic colloids (fiber)
Absorb water and form bulk, emollient gel that distends colon (increases stool mass)
Promotes peristalsis -> get rid of food more easily
Stool Surfactant Agents (Softeners)
Docusate (oral or enema - fluid through rectum)
Glycerin (rectal suppository - solid medication through rectum)
Mineral oil (oral)
Stool Surfactant Agents (Softeners) MOA
Lowers surface tension allowing water and lipids to penetrate
Mineral oil lubricates + retards water absorption from stool - so stools still fluid to be passed out
Stool Surfactant Agents (Softeners) concerns
Aspiration can result in severe lipid pneumonitis
Long-term use can impair absorption of fat soluble vitamins (A, D, E and K)
Osmotic Laxatives
nonabsorbable sugars/salts - sorbitol, lactulose, Mg(OH)2, sodium phosphate polyethylene glycol (PEG)** - balanced with osmotically active sugars -> better choice! avoids significant electrolyte shifts
osmotic laxatives MOA
Osmotically-mediated water movement into bowel increases stool liquidity and volume
Increased volume stimulates peristalsis
High doses can produce bowel evacuation (purgation) within 1 to 3 hours
osmotic laxatives ADR
colonic bacteria act on the introduced sugars -> flatus and abdominal cramps
need to maintain adequate hydration
sodium phosphate: hypernatremia, hypocalcemia, hypokalaemia
may cause cardiac arrhythmias or acute renal failure due to tubular deposition of calcium phosphate
osmotic laxatives (sodium phosphate) contraindications
Should not be used in patients who are frail, elderly, on diuretics, unable to maintain adequate hydration or who have renal insufficiency or cardiac disease
Stimulant Laxatives (Cathartics)
Anthraquinone Derivatives:
Aloe, Senna and Cascara (oral or per rectum)
Diphenylmethane Derivatives:
Bisacodyl (faster bowel movement effect if done through rectum, also can be oral): used for bowel prep before colonoscopy
Stimulant Laxatives MOA
Produce migrating colonic contractions
Colonic electrolyte and fluid secretion
Stimulant Laxatives ADR
chronic use may lead to dependence -> long term use
brown pigmentation of the colon
Chloride Channel Activators drug
Lubiprostone
Chloride Channel Activators MOA
Stimulate type 2 chloride channels (ClC-2) in small intestine
Increases chloride-rich fluid secretions
Stimulates motility and shortens intestinal transit time
Chloride Channel Activators ADR + contraindication
return of constipation after discontinuation of drug
nausea caused by delayed gastric emptying
NO PREGNANCY
Opioid Receptor Antagonists
Methylnaltrexone bromide - more for palliative patients
1st line for cancer!!* subcutaneous injection every 2 days
Alvimopan - post GI surgery:
Orally ≤5 hrs before surgery & twice daily after surgery (not >7 days)
Opioid Receptor Antagonists MOA
treatment for opioid induced constipation
blockade of intestinal mu (μ) opioid receptors
– Does not readily cross blood-brain barrier so do not block CNS analgesic effects**
Opioid Receptor Antagonists ADR
only for short term use in hospitalised patients cause of risk of CVS toxicity
5-HT4-Receptor Agonists drugs (2)
Cisapride
Prucalopride
5-HT4-Receptor Agonists MOA
Stimulation of presynaptic 5-HT4 receptors on submucosal intrinsic primary afferent neurone (IPAN) terminals enhances release of neurotransmitters -> stimulate enteric neurons (EN) to promote peristaltic reflex and colonic mass movement
5-HT4-Receptor Agonists ADR
Cisapride: partial agonist. adverse CVS effects due to actions at hERG K+ channel
Prucalopride: high affinity agonist. no CVS effects
Drugs for diarrhoea
(BLOCKS)
Opioid Agonists - time
Colloidal Bismuth Compounds - stool freq and liquidity
Kaolin (clay) and Pectin (indigestable carbohydrate from apples) - stool liquidity
Bile Salt-Binding Resins
Somatostatin-like Peptides - motility
Lyophilizate of killed Lactobacillus acidophilus - intestinal flora
Opioid Agonists drugs (2)
Loperamide
Diphenoxylate
Opioid Agonists MOA
effects in ENS (enteric nervous system): increase colonic transit time
Opioid Agonists ADR
CNS effects: addiction and abuse; dependence - for diphenoxylate: given with atrophine (se: dry mouth) to discourage overdose
Colloidal Bismuth Compounds
Bismuth subsalicylate
Bismuth subcitrate potassium
Colloidal Bismuth Compounds MOA
has antimicrobial effect and binds enterotoxins
which has benefit for treating traveller’s diarrhoea
mucosal protective
agents in acid-peptic diseases
salicylate: inhibits intestinal prostaglandin production and chloride secretion,
reduces stool frequency and liquidity in acute infectious diarrhoea - more solid poop
Kaolin and pectin MOA
Absorbents of bacterial toxins and fluid
Decrease stool liquidity and number
for acute diarrhoea
Kaolin and pectin ADR
bind to and inhibit absorption of other medications -> should not be taken within 2hrs of other medication
not absorbed so less risk of adverse effects
Bile Salt-Binding Resins (3)
Cholestryamine
colestipol
colesevelam
Bile Salt-Binding Resins MOA
bind to bile salts alleviating diarrhoea caused by excess fecal bile salts - because of malabsorption of bile salts due to disease of the ileum (conjugated bile salts are normally absorbed in the terminal ileum)
Bile Salt-Binding Resins ADR
Bloating, flatulence, constipation and fecal impaction
Exacerbation of malabsorption of fat if underlying deficiency is present
affects absorption of other medication -> take 2hrs apart
Somatostatin-like Peptide drugs (2)
somatostatin (super short - 3min - T1/2 through IV)
Octreotide (longe T1/2=1.5hrs)
Somatostatin-like Peptides MOA
Inhibition of release of various transmitters and hormones (e.g. gastrin, VIP, 5-HT)
Reduces intestinal and pancreatic secretions
Slows gastrointestinal motility and inhibits gallbladder contraction
For secretory diarrhoea caused by gastrointestinal neuroendocrine tumours/ vagotomy/ gastric dumping syndrome (rapid gastric emptying)/ short bowel syndrome/ AIDS
Somatostatin-like Peptides ADR
reducing pancreatic secretions: cause steatorrhea -> fat-soluble (ADEK) vit def
Nausea, abdominal pain, flatulence and diarrhoea
Formation of gall sludge or gallstones in 50% of patients
Prolonged treatment can result in hypothyroidism/ bradycardia
Lyophilizate of killed Lactobacillus acidophilus
Lacteol forte - mixed w/ water
Lyophilizate of killed Lactobacillus acidophilus MOA
for travellers diarrhoea
Adheres onto the surface of intestinal cells and normalizes the intestinal flora by competitive exclusion
Prevents over colonization of these organisms
Lyophilizate of killed Lactobacillus acidophilus ADR
+ contraindication
not systemically absorbed = little risk of ADR
need to maintain hydration
contraindicated in pts with lactose intolerance
Activated charcoal MOA
used for emergency treatment of certain types of poisoning: prevents poison from being absorbed from the stomach into the body
not proven to treat diarrhoea yet - might bind to enterotoxins and prevent infectious diarrhoea?
Activated charcoal ADR
nausea and vomitting
risk of charcoal entering the lungs -> respiratory side effects: bronchiolitis obliterans, empyema, and Adult Respiratory Distress Syndrome
interferes with absorption of other nutrients/drugs
