Lecture 67

Question 1

characteristics of IBS

Answer 1

abdominal pain or cramping and changes in bowel including bloating, gas, diarrhea, and constipation

Question 2

risk factors of IBS

Answer 2

2:1 ration in women vs men
younger than 50 when diagnosed
lower socioeconomic status
only 15% seek medical attention
1 in 5 US adults

Question 3

IBS epidemiology

Answer 3

chronic condition (a relapsing and remitting disorder)
does not cause inflammation, changes in bowel tissue, or increase risk of colorectal cancer

Question 4

pathophysiology of IBS

Answer 4

unclear
abdominal pain associated with abnormal BM
perhaps due to somatovisceral and motor dysfunction of intestine

Question 5

contributing factors of IBS

Answer 5

host
luminal
environmental

Question 6

host factors of IBS

Answer 6

altered gastrointestinal motility
visceral hypersensitivity
altered brain-gut interactions
increased intestinal permeability
gut mucosal immune activation

Question 7

luminal factors of IBS

Answer 7

dysbiosis
neuroendocrine mediators
bile acids

Question 8

environmental factors of IBS

Answer 8

psychosocial distress
food medications
supplements
antibiotics
enteric infection

Question 9

diagnostic criteria for IBS

Answer 9

recurrent abdominal pain or discomfort for at least 1 day per week in the previous month on average
2 of the following: increase in pain related to defecation, associated with change in frequency of stool, or associated with change in appearance of stool
symptom onset should occur at least 6 months prior to diagnosis

Question 10

subtypes of IBS

Answer 10

IBS-C
IBS-D

Question 11

IBS-C treatment

Answer 11

step 1 - increase fiber and fluid intake (avoid foods also)
step 2 - add bulk-forming laxatives (soluble fiber psyllium, peg)
step 3 - consider adding anti-spasmodic or anticholinergic agent for GI symptoms (hyoscyamine, dicyclomine)
step 4 - consider lubiprostone or linaclotide for treatment of constipation and abdominal pain
step 5 - psychotherapeutic behavior mods, consider antidepressants (SSRIs)
step 6 - consider serotonin-4 agonist (Tegaserod) as last line

Question 12

IBS-D treatment

Answer 12

step 1 - dietary mods (consider eliminating lactose and caffeine)
step 2 - add loperamide or anti-spasmodic agent (dicyclomine)
step 2a - replace with eluxadoline if pain persists
step 2b - consider rifaximin
step 3 - add serotonin-3 antagonist (alosetron)
step 4 - psychotherapeutic behavior mod, consider antidepressants (TCAs)

Question 13

fiber, bulk-forming agents and laxatives in IBS-C

Answer 13

STEP 2 after dietary modifications in IBS-C
soluble fiber psyllium (mechanism - increase stool volume; AE - some fiber contain FODMAPs which can worsen symptoms)
PEG (mechanism - osmotic)

Question 14

anti-spasmodic therapy

Answer 14

step 3 in IBS-C
hyoscyamine (levsin), dicyclomine
mechanism - block ACh on PS receptors; improve abdominal pain

Question 15

anti-spasmodic therapy AE

Answer 15

hyoscyamine - dizziness, somnolence, blurred vision
dicyclomine - dry mouth, dizziness, decreased appeptite, blurred vision

Question 16

education on anti-spasmodic

Answer 16

use caution in elderly (on BEERS list)
avoid in patients with glaucoma, IBS-C
benefits in post-meal abdominal pain, gas, bloating, and fecal urgency
most frequently used pharmacotherapy agents for IBS

Question 17

antidepressants (SSRIs)

Answer 17

step 5 in IBS-C
drugs - citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline
mechanism - reduce visceral sensitivity
AE - transient NV; sexual dysfunction; sedation; insomnia

Question 18

antidepressant (SSRIs) education

Answer 18

generaly used at doses lower than used for depression/anxiety in IBS-C
SNRIs are similar but less data is available

Question 19

pro-secretory agents in IBS-C

Answer 19

step 4 in IBS-C
drugs - lubiprostone (Amitiza) and linaclotide

Question 20

lubiprostone in IBS-C

Answer 20

AE - containdicated if suspected intestinal block
higher dose (24mcg bid) approved for chronic idiopathic and OIC

Question 21

linaclotide in IBS-C

Answer 21

AE - diarrhea (worsened with high fat meals)
BBW - against use in children under 17yo due to dehydration

Question 22

5HT4 agonist in IBS-C

Answer 22

tegasrod
step 6
only available through the FDA under the emergency investigation drug protocol
mechanism - stimulates peristalsis and GI secretion; modulates visceral sensitivity
AE - HA, abdominal pain, dizziness, diarrhea, CV events

Question 23

anti-diarrheal agents in IBS-D

Answer 23

step 2
drugs - loperamide and lomotil
effective at reduce diarrhea; not effect on abdominal pain

Question 24

loperamide in IBS-D

Answer 24

mechanism - inhibits peristalsis and GI secretion; modulates visceral sensitivity
AE - constipation; higher risk of dependence/abuse

Question 25

opioid receptor agonist in IBS-D

Answer 25

step 2a
eluxadoline (viberzi)
contraindicated in patients with history of pancreatitis, alcoholism, over 3 alcoholic drinks per day, child pugh class C
C-4 schedule due to euphoric feeling and abuse potential

Question 26

5HT3 Receptor antagonists in IBS-D

Answer 26

alosetron (lotronex)
step 3
BBW - rare but serious ischemic colitis

Question 27

Rifaximin (Xifaxan) in IBS-D

Answer 27

step 2b
mechanism - poorly absorbed non-systemic broad spectrum antibiotic that targets the gut
AE – dizziness, fatigue, peripheral edema

Question 28

antidepressants (TCAs) in IBS-D

Answer 28

drugs - notriptyline, amitriptyline, trimipramine, desipramine
mechanism - reduce visceral sensitivity; decrease stress

Question 29

antidepressant (TCAs) AE and Education in IBS-D

Answer 29

constipation, dry mouth, drowsiness, weight gain, risk of QT-prolongation
notes - most beneficial in patients with IBS; generally used at lower dose than used for depression or anxiety