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Year 3 - Clinical (Winter) > 18 - IBS > Flashcards

18 - IBS Flashcards

1
Q

Definition of IBS

A
  • Recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated w/ at least 2 features:
    • Improvement w/ defecation
    • Onset associated w/ a change in stool frequency
    • Onset associated w/ a change in stool form (appearance)
  • Criteria need to be met for at least 3 months w/ onset at least 6 months prior to making the diagnosis
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2
Q

Features of IBS

A
  • Other supporting features = mucous in stool, bloating and distention
  • Key features = abdominal pain or discomfort associated w/ altered bowel pattern
  • ROME III provides subtyping of IBS based on predominant stool pattern:
    • W/ constipation
    • W/ diarrhea
    • Mixed
    • Unsubtyped
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3
Q

Characterization of IBS

A
  • Characterized in terms of multiple physiological determinants contributing to a common set of sx
  • A group of disorders rather than a single disease
  • Difficult to generalize as sx vary among people
  • IBS px have higher rates of non-GI sx including headache, back pain, fatigue, myalgia
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4
Q

Pathophysiology of IBS

A
  • Nervous system (brain gut interactions)
    • CNS and enteric NS
  • Gut flora issues -> post infectious, bacterial overgrowth
  • “Its all in your head”
    • Altered sensitivity to gut distension
    • Altered signaling processes in CNS
    • Altered motor response (ex: hormones)
    • Other perception issues include genetics and psychosocial
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5
Q

Alarm features of IBS

A
  • Weight loss ( >5 kg)
  • Bloody stools
  • Severe diarrhea
  • Recurring fever
  • Onset > 50 y/o
  • Family history of colon cancer, IBD
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6
Q

Psychologic disorders

A
  • Present in minority of all IBS px
  • Present in majority of IBS seeking subspecialist care
  • IBS sx aren’t manifestations of psychological disorders but comorbidity increases likelihood to seek subspecialist
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7
Q

IBS therapy

A
  • Location, severity, previous response to therapy involved in selection process
  • IBS subtypes are highly unstable
  • Predominant sx guide most therapeutic plans
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8
Q

Non-drug therapy for IBS

A
  • Look for sources of constipation and diarrhea
  • Constipation -> low fiber diet, lack of exercise, medications, muscular atony or decreased abdominal pressure, metabolic abnormalities
  • Diarrhea -> foods, lactose, sorbitol, fructose
  • Establish “therapeutic” relationship w/ pt
  • Regulate dietary fiber intake
  • Avoid precipitants (ex: foods that trigger abdominal pain)
  • Avoid excesses (ex: caffeine, fruit intake, carbonated drinks, gum)
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9
Q

Behavioural therapies for IBS

A
  • Relaxation
  • Biofeedback
  • Hypnotherapy
  • Cognitive behavioural (CBT)
  • Psychotherapy
  • Evidence that these are more effective than placebo for some sx of IBS
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10
Q

CBT for IBS

A
  • Short term intervention oriented toward change, especially developing strategies to cope
  • Describes how thoughts, emotions, events and physiologic responses are interlinked
  • Education, monitoring of thoughts, emotions and how they are related, testing assumptions, stress management, and planning activities
  • Best for those w/ some medical intervention, still distressed and open to active involvement in CBT
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11
Q

Drug therapy for IBS

A
  • Has been very difficult to find new drugs that work
  • Difficult to see a good response to a single drug in most people
  • Very high placebo response rate
  • Only a minority of those w/ IBS need extended drug therapy
  • Consider when IBS sx are impacting QoL
  • Short term response over a few weeks reported w/ many therapies
  • Generally, need 3-4 weeks to assess efficacy; antidepressants may be a bit longer
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12
Q

Problems w/ IBS studies

A
  • Hard to compare pt populations between studies
  • Lack of reproducibility
  • Need to develop better definitions of functional bowel conditions to lead to better controlled data to interpret clinical studies
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13
Q

Pharm options for IBS w/ constipation

A
  • Fiber based products
  • Osmotic and salt laxatives
  • Stimulant laxatives
  • Prucalopride
  • Linaclotide, lubiprostone
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14
Q

Fiber based products for IBS w/ constipation

A
  • May provide beneficial effects through a number of mechanisms:
    • Increase stool bulk and frequency
    • Improve GI transit time
    • Reduce gas/bloating by binding bile salts
  • No evidence of benefit over placebo relieving global IBS sx
  • Best benefit likely in abdominal pain and constipation
  • Can get through diet or manufactured agents
  • Bloating more likely on high doses; may increase gas produced in intestines
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15
Q

Osmotic and salt laxatives

A
  • Lactulose -> gas, bloating, and taste a problem
  • Magnesium -> poorly absorbed, act as osmotic laxative
  • Phosphate
  • PEG based
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16
Q

Stimulant laxatives

A
  • Senna based and Bisacodyl
  • Quicker onset (< 24 h)
  • SE = cramping
17
Q

Approach w/ laxatives for IBS

A
  • Often start w/ a regimen as a regular routine and build or subtract from there
  • Ex: start w/ senokot 2 tabs HS, after 3 days if no improvement, add on something else or increase to 4 tabs HS
18
Q

Prucalopride (Resotran)

A
  • Serotonin 4 receptor agonist
  • Much lower affinity to hERG channel than cisapride
  • Labelled indication for chronic idiopathic constipation in adult females w/ inadequate response to laxatives
  • Primary action is via stimulation of colonic transit
  • Renal clearance
  • Not recommended in pregnancy
  • SE = nausea, diarrhea; may be dose related
  • Not covered by plans, about $3/day
19
Q

Linaclotide (Constella, Linzess)

A
  • Peptide guanylate cylase-C (GCC) agonist
  • Indirectly activates cystic fibrosis transmembrane conductance regulator => secretion of Cl and bicarb into bowel and increased transit
  • Approved for IBS C and chronic constipation
  • Frequent SE = diarrhea
  • Not approved for plan coverage
20
Q

IBS w/ constipation – summary

A
  • Dietary measures w/ bran or psyllium usually a good place to start
  • If fiber fails, consider osmotic laxative (ex: magnesium) and/or stimulant (ex: senna, Bisacodyl)
  • Add on therapy w/ lactulose or PEG based products
  • Linaclotide or prucalopride for refractory cases
21
Q

Pharm options for IBS w/ diarrhea

A
  • Loperamide
  • Cholestyramine
  • Alosetron
  • Fiber
  • Newer agents = eluxadoline, rifaximin
22
Q

Loperamide - MOA, SE, dose

A
  • Increased transit time, water and electrolyte absorption, and anal sphincter tone
  • Some evidence to improve stool consistency and abdominal pain over placebo
  • Lack evidence in decreasing global IBS sx
  • May use Lomotil or codeine in refractory cases
  • Can be used prophylactically (ex: prior to travel, stressful situation)
  • SE = bloating may be worsened, abdominal pain may develop
  • Dose = 2-4 mg up to QID
23
Q

Cholestyramine

A
  • 3rd line in IBS w/ diarrhea
  • Can be used as add on therapy w/ other agents
  • Issues w/ taste and drug interactions
  • Often hit or miss agent, so review benefit
24
Q

Eluxadoline (viberzi, truberzi)

A
  • Mu opioid agonist and delta opioid receptor antagonist

- Minimally absorbed, acts locally for IBS w/ diarrhea

25
Q

Alosetron (Lotronex)

A
  • Serotonin 3 receptor antagonist
  • Better than placebo in IBS w/ diarrhea, improves overall sx
  • Major concerns w/ ischemic colitis lead to withdrawal from US market; can still obtain via approval process
26
Q

Fiber for IBS w/ diarrhea

A
  • Used to increase stool consistency

- Target fiber intake usually around 30 g/day but start lower and gradually increase to reach target

27
Q

IBS w/ diarrhea – summary

A
  • Exclude lactose intolerance, celiac disease and other sources in diet for diarrhea
  • Antidiarrheals usually first line w/ loperamide preferred agent
  • Add in fiber slowly if used to increase stool consistency
28
Q

IBS w/ bloating and gas

A
  • These px less likely to obtain benefit w/ drugs than IBS w/ constipation or diarrhea
  • Diet changes and limited fiber intake as can worsen both sx
  • Antidepressants have a role
  • Antispasmodics considered
  • Data on promotility agents less certain
29
Q

Recommendations for IBS w/ gas

A
  • Some foods associated w/ increased gas formation (ex: beans, onions, celery)
  • Gas expulsion stimulated w/ food and exercise (go for a walk after meals)
30
Q

Antispasmodics

A
  • Primarily act via decreasing spontaneous smooth muscle stimulated movements (directly or via anticholinergic or antimuscarinic mechanisms)
  • May provide relief of abdominal pain, distension or bloating (take pre-meals)
  • Can occasionally be used for sx management of IBD as well
  • Most SE are anticholinergic
  • Belladonna, clidinium, dicyclomine, hyoscyamine, pinaverium, propantheline, trimebutine
  • Used to be prescribed frequently, px often on them daily for long periods of time
  • Generally, not recommended for regular basis as tolerance may develop
  • Systematic reviews of the agents generally say no better than placebo
31
Q

IBS and pain

A
  • Behaviour and aversion techniques can be employed
  • Antidepressants and NSAIDs used in refractory cases
  • Narcotic analgesics usually not successful
32
Q

Antidepressants for IBS

A
  • Visceral hypersensitivity (increase pain/ discomfort vs. non-IBS for same degree of colon distension)
  • Increases pain threshold; may also affect GI motility
  • 6-12-week RCTs didn’t show improvement in abdominal pain w/ SSRIs, modest relief w/ TCAs
  • Response may vary amongst the agents (may try more than 1 agent)
  • TCAs most studied (amitriptyline, desipramine); some data w/ SSRIs
  • Used in chronic pain doses (low dose) rather than depression doses
33
Q

Antibiotics and probiotics for IBS

A
  • Antibiotics -> data that they help/worsen IBS, bacterial overgrowth
  • Probiotics -> competition w/ pathogenic bacteria, anti-inflammatory effects, don’t know which ones to use and in what doses
34
Q

What are probiotics and which are most studied?

A
  • Live microorganisms which when administered in adequate amounts confer a health benefit on the host
  • Most studied = lactobacilli and bifidobacterial alone or in different combinations
35
Q

Probiotics in IBS

A
  • Problem is most of GI flora is anaerobic and many strains are difficult to capture and grow
  • Multiple month sampling has reported more instable intestinal flora in IBS and bacterial overgrowth px
  • Studies don’t find consistent findings w/ these mechanisms
  • Bacteria from probiotic are generally cleared from GI tract w/in 1 week after last ingestion
  • Real trial evidence overall still weak (most studies are small, significant placebo response in trials)

Year 3 - Clinical (Winter) (30 decks)

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