IBS Flashcards
What is IBS
a chronic GI disorder with abdominal pain and altered bowel habits
What causes IBS
Visceral hypersensitivity altered bowel motility neurotransmitter imbalance infection psychosocial factors
Symptoms of IBS are
abdominal pain distention bloating indigestion various Sx of defecation
What are the 3 subcategories of IBS
Pain with diarrhea
Pain with constipation
Pain with diarrhea and constipation
Patients with IBS can self administer meds to alleviate these Sx
headache sleep disturbance MSK chest pain nausea heartburn back pain
Foundation for treating IBS is
diet and lifestyle modification
Low FODMAP diet (fermentable oligo-, di-, and monosaccharides and polyols)
Exclude foods that increase flatulence, alcohol, and caffeine
Exercise
What foods are in FODMAP
O: wheat, barley, rye, onion, cashew, pistacchio, legumes, chickpeas
D: lactose
M: apple, pear, mango, cherries, asparagus
P: apricots, nectarines, mushrooms
(there are a ton more i didn’t write)
Pharm therapy principle for treating IBS is
Tx directed at relieving abdominal pain and improving bowel function
For diarrhea predominant IBS, initial Tx is
antidiarrheal agent- Loperamide
For constipation predominant IBS, initial Tx is
Fiber to soften stool and reduce straining (but be careful bc increased gas production can exacerbate bloating)
1. Psyllium/ispaghula
if this fails, try Polyethylene glycol
Alternate: Lubiprostone, Linaclotide
What serotonin receptors are in the gut
Type 3 (5-HT3) Type 4 (5-HT4) They are responsible for secretion, sensitization, and motility
What is polyethylene glycol
Osmotic laxative
Improves constipation but NOT abdominal pain
Start w/ 17g powder in 8oz water, titrate up or down. Max 34g
ADE of PEG are
Bloating
Abdominal discomfort
What is Lubiprostone
Prostanoic acid derivative
Stimulates T2 chloride channels in small intestine= increase chloride secretion into sm. int= stimulate intestinal motility and shorten transit time
Good for women 18+ w/ IBS-C, efficacy for men unproven
ADE for Lubiprostone are
Nausea 2/2 delayed gastric emptying
Pregnancy category C, increased fetal loss in guinea pigs
Dose must be reduced if w/ severe hepatic impairment
What is Guanlyate Cyclase-C Agonist Linaclotide (Linzess)
Stimulates intestinal fluid secretion and transit time
Good for those with persistent constipation where PEG didn’t work- improves abdominal pain, bloating, straining, stool consistency, and spontaneous BM x week
290 mcg daily
MC side effect of Linzess is
Diarrhea
What is Tegaserod
5-HT4 agonist that stimulates the release of NT and increases colonic motility
Used only for emergent Tx of IBS with constipation in women <55 y/o
Do we like Tegaserod
No, it was voluntarily removed from the market (except for emergency) 2/2 increased # of CV death
What does Loperamide do
Inhibit peristalsis Prolong transit time Reduce fecal volume Decrease stool frequency and consistency, but does NOT relieve bloating, abd pain, or global IBS Sx Take 2mg 45 min before meal Good for alternating IBS!
What is Eluxadoline (Viberzi)
Mixed mu&kappa-opioid receptor agonist, and delta antagonist
Reduces abdominal pain and diarrhea w/o constipating effects
BUT has abuse potential!
Contraindications to Eluxadoline are
biliary d/o
pancreatitis (esp. severe in those w/o a gallbladder)
severe liver impairment (adjust dose)
heavy alcohol use
MC ADE of Eluxadoline are
nausea, constipation, abdominal pain
pancreatitis in those w/ biliary d/o or alcoholics
CNS depression
What is second line for IBS-D
Bile acid sequestrants (Cholestyramine, colestipol, colesevelam)
GI ADE of Bile Acid Sequestrants are
bloating
flatulence
abdominal discomfort
constipation
What are 5-HT3 antagonists
Ondansetron, Granisteron, Dolasteron, Palonosteron
Inhibiting this receptor stops the activation of afferent pain sensation from gut to spinal cord/CNS
= Less visceral pain, nausea, and bloating
Ondansetron and the other %-HT3 antagonists can also be used to Tx
Nausea and vomiting (zofran!)
5-HT3 receptor block on terminals of enteric cholinergic neurons inhibits
colonic motility, esp. in left colon= increased total transit time
Alsoteron is good for
women with severe IBS-D who did not respond to conventional therapies, and have been educated on risks
efficacy in men not established- not used for them
What are the PK of Alosteron
Very potent 5-HT3 antagonist
rapidly absorbed from GI tract (duration longer than 1/2 life makes it seem)
Extensive hepatic CYP450 metabolism
Renal excretion
Dissociates slower than other 5-HT3 antag. b/c it binds with higher affinity receptors
What is the efficacy of Alosteron
Reduce IBS related lower abdominal pain, cramps, urgency, and diarrhea
Leads to reduction in mean # of BM per day, and stool consistency
ADE of Alosteron are
rare but serious GI toxicity Constipation Hospitalization or surgery Episodes of ischemic colitis -Requires FDA approved restricted program
Alosteron interacts with
Nothing significant! Even though it is a CYP450 enzyme
Chronic abdominal pain in IBS can be treated with
Low dose TCA (Amitryptaline, Desipramine)- they’re anticholinergics!
They alter central processing of visceral afferent information; Reduce stool frequency and liquidity; Alter NT receptors (serotonin) affectung visceral sensation
What anti-spasmodics are used in IBS
Dicyclomine and Hyoscyamine
They inhibit muscarinic cholinergic receptors in enteric plexus and smooth muscle
Use low dose to avoid autonomic effects
not usually used 2/2 efficacy not convincingly proven
ADE of high dose anti-spasmodics are
dry mouth visual disturbance urinary retention constipation (anticholinergics)
