lower GI drugs

Question 1

what is the moa of Fiber / Bulk-Forming agents

Answer 1

Recommended because they approximate physiological mechanism (facilitate passage and stimulate peristalsis via absorption of water and subsequent bulk expansion)

Question 2

name a fiber/bulk forming laxative agent

Answer 2

psyllium

Question 3

name the Saline (osmotically active agents) Cathartics

Answer 3

polyethylene glycol
Milk of magnesia [Mg (OH2)], 
magnesium citrate,
phosphate enemas
lactulose

Question 4

what is Bisacodyl

Answer 4

a laxative in the Stimulant / Irritant catergory.
Thought to act via increase in peristaltic activity by inducing low-grade inflammation (local irritation) in bowel to promote accumulation of water and electrolytes and stimulation of intestinal motility

Question 5

what is Dicyclomine

Answer 5

Antispasmodics. Reduces abdominal spasms and cramps via smooth muscle relaxation (direct myorelaxant effects or antimuscarinic mechanisms). Often used prn for acute attacks of abdominal pain or before meals if postprandial symptoms. Modest efficacy - caution if IBS-C.

Question 6

what is the Mechanism of action for Lubiprostone:

Answer 6

Prostaglandin analog that activates chloride channels, stimulating intestinal fluid secretion.

Question 7

what are the clinical uses of Lubiprostone

Answer 7

Approved for IBS-C in women ≥ 18 years old; also used for opioid -induced constipation

Question 8

what are the adverse effects of Lubiprostone

Answer 8

Nausea and diarrhea

Question 9

what is a DDI of Lubiprostone to be aware of?

Answer 9

Methadone may reduce activation of Cl- channels by lubiprostone (DDI)

Question 10

What is the Mechanism of action of Linaclotide (Linzess):

Answer 10

Activates guanylate cyclase-C on intestinal epithelium with increased cGMP, resulting in increased luminal intestinal secretions and accelerated intestinal transit

Question 11

what are the clinical uses of Linaclotide (Linzess)

Answer 11

IBS-C and chronic idiopathic constipation (CIC)

Question 12

what are the adverse effects of Linaclotide (Linzess)

Answer 12

Diarrhea,
abdominal pain,
flatulence,
abdominal distention

Question 13

•what is the mechanism of action for Tegaserod (Zelnorm)

Answer 13

Agonist at 5-HT4 receptors -> stimulation of peristaltic reflex, promoting gastric emptying and intestinal motility

Question 14

what is the clinical use of tegaserod?

Answer 14

Withdrawn in 2007 - available for emergency use through FDA for IBS-C patients or chronic idiopathic constipation who have not responded to other treatments.

Question 15

what are the Adverse reactions of tegaserod.

Answer 15

Link with heart attacks, strokes, and unstable angina led to withdrawal

Question 16

What is the Mechanism of action for Alosetron.

Answer 16

Block of 5-HT3 receptors on sensory and motor neurons reduces pain and inhibits colonic motility

Question 17

what is the Clinical use alosetron?

Answer 17

Alosetron is restricted to use only for treatment of severe IBS-D in women that have not responded to conventional therapies. Effective in 50-60% of patients.

Question 18

what are the adverse effects of alosetron

Answer 18

Constipation in 30% of patients, requiring discontinuation in 10%. Ischemic colitis in 3 of 1000 patients with some fatalities has led to restricted use.

Question 19

what is rifamaxin?

Answer 19

Minimally absorbed oral antibiotic thought to alter gut flora and may reduce mucosal inflammation and visceral hypersensitivity. used IBS-D

Question 20

Loperamide, and OTC opioid agonist - prn use can reduce ________

Answer 20

postprandial urgency and stool frequency