IBS treatment

Question 1

What are some types of drugs used to treat IBS?

Answer 1

Loperamide
Bulk forming laxatives
Osmotic cathartics
TCAs
SSRIs
5-HT3 antagonist
5-HT4 agonist

Question 2

Which TCAs are used to treat IBS?

Answer 2

Amitryptaline

Desipramine

Question 3

What is the MoA of TCA use to treat IBS?

Answer 3

Anticholinergic side effect –> treats diarrhea-predominant IBS

Question 4

Which SSRIs are used to treat IBS?

Answer 4

Paroxetine
Fluoxetine
Sertaline

Question 5

What is the MoA of SSRI use to treat IBS?

Answer 5

Side effect –> treat constipation-predominant IBS

Question 6

What is an example of a 5-HT3 antagonist?

Answer 6

Alosetron

Question 7

What is the MoA of alosetron?

Answer 7

Reversibly inhibits 5-HT3 receptors

Question 8

What is the usual result of 5-HT3 activation?

Answer 8

5-HT3 → stimulation of vagal afferents → activation of interneurons containing NO or VIP → inhibition of ACh motoneurons → decreased contractility

Increasing contractility throws off timing of peristalsis –> longer transit time

Question 9

When is alosetron used?

Answer 9

Women with non-responsive diarrhea-predominant IBS

Question 10

What are the possible side effects of alosetron?

Answer 10

Constipation (30%)
Ischemic colitis (0.3%)

Worse with concomitant use of CYP1A2 inhibitors

Question 11

What is an example of a 5-HT4 agonist?

Answer 11

Tegaserod

Question 12

What is the MoA of tegaserod?

Answer 12

Activation of 5-HT4 receptor –> release of CGRP from submucosal and myenteric plexuses –> stimulation of the peristaltic reflex

Question 13

What are some pharmacokinetics of tegaserod?

Answer 13

Metabolized in the liver
Excreted in urine
Low bioavailability…even lower after eating

Question 14

When is tegaserod used?

Answer 14

For constipation-predominant IBS

Question 15

What are some side effects of tegaserod?

Answer 15

Prolonged QT (in drugs of same class) –> restricted use
Diarrhea in first few days of treatment
Headache