IBS

Question 1

Lactulose

Answer 1

MOA: metabolized by colonic bacteria to formic
and acetic acid –> increases motility and secretion
breakdown increases osmotic pressure

Use: constipation
* Also used for hepatic encephalopathy (more later)

AEs: abdominal pain, flatulence, diarrhea

Question 2

Lubiprostone

Answer 2

MOA: stimulates EP4 receptors (coupled to Gs)
on GI epithelial cells –> increases chloride channel activity –> increases fluid and electrolyte secretion –> increases motility

Use: constipation

AEs: nausea

Question 3

Linaclotide

Answer 3

MOA: stimulates receptor coupled to GC-C
receptor on GI epithelial cells –> increases chloride channel activity –> increases fluid and electrolyte secretion –> increases motility

Use: constipation

AEs: diarrhea, abdominal pain

Question 4

Loperamide, Diphenoxylate w/atropine

Answer 4

MOA: μ receptor agonist –> increases nonpropulsive contractions and decrease propulsive contractions –> increase transit time

Use: “peripherally restricted” to treat diarrhea

AEs:
Constipation
High doses (diphenoxylate) –> atropine causes dysphoria from antimuscarinic effects

Question 5

Hyoscyamine

Answer 5

MOA: blocks M3 on GI smooth muscle –> decrease contractions
“antispasmodic”

Use: abdominal pain

AEs:
Antimuscarinic